The Division Meeting aims at presenting the status of the activities within the Seismology Division and its place within EGU. Statistics of abstracts within the seismology division and EGU and introduce the outstanding researchers, awarded the Beno Gutenberg medal and the Early Career Scientist award.

The session General Contributions on Earthquakes, Earth Structure, Seismology features a wide range of presentations on recent earthquakes and earthquake sequences of local, regional, and global significance, as well as recent advances in characterization of Earth structure using a variety of methods.

The broad scale tectonics of the Eastern Mediterranean is dominated by the interaction of the Nubian and Arabian plates with the Eurasian plate. This complex tectonic frame exhibits almost all types of plate boundary conditions such as continental collision and extension, oceanic subduction, and continental transform. The evolution and present deformation are constrained by diverse geological, geophysical, and geodetic observations and have been explained by different hypotheses, such as (a) tectonic escape system caused by the post-collisional convergence of Eurasian and Arabian plates creating forces at its boundaries with gravitational potential differences of the Anatolian high plateau (b) asthenospheric flow dragging the circular flow of lithosphere from the Levant to Anatolia in the east and the Aegean in the west, (c) slab pull of the Hellenic subduction, (d) mantle upwelling underneath Afar and with the large-scale flow associated with a whole mantle, Tethyan convection cell, (e) or combinations of these mechanisms for the Eastern Mediterranean. Naturally, this tectonic setting generates frequent earthquakes with large magnitudes (M > 7), forming a natural laboratory on understanding the crustal deformation, and crust-mantle interactions for various disciplines of active tectonics.

Multidisciplinary studies, especially within the last three decades, have made significant contributions to our understanding of the processes on the crustal deformation, and interaction of the mantle with the crustal processes of this region. With this session, we aim to bring together the recent findings of these studies, thus we welcome/invite contributions from a wide range of disciplines including, but not limited to, neotectonics, seismology, tectonic geodesy (e.g. GNSS, InSAR), palaeoseismology, tectonic geomorphology, remote sensing, structural geology and geodynamic modelling, which geographically cover the Eastern Mediterranean region, including Anatolia-Aegean Block, Caucasus, Iran, Middle East and Greece.

The Tethyan orogenic belt is one of the largest and most prominent collisional zones on Earth. The belt ranges from the Mediterranean in the west to Papua New Guinea in the east. It results from the subduction and closure of multiple basins of the Tethys Ocean and the subsequent collision of the African, Arabian and Indian continental plates with Eurasia. Its long-lasting geological record of the opening and closure of oceanic basins, the accretion of arcs and microcontinents, the complex interactions of major and smaller plates, and the presence of subduction zones at different evolutionary stages, has progressively grown as a comprehensive test site to investigate fundamental plate tectonics and geodynamic processes with multiple disciplines. Advances in a variety of fields provide a rich and growing set of constraints on the crust-lithosphere and mantle structure and their physical and chemical characteristics, as well as the tectonics and geodynamic evolution of the Tethyan orogenic belt.

We welcome contributions presenting new insights and observations derived from different perspectives, including geology (tectonics, stratigraphy, petrology, geochronology, geochemistry, and geomorphology), geophysics (seismicity, seismic imaging, seismic anisotropy, gravity), geodesy (GPS, InSAR), modelling (numerical and analogue), natural hazards (earthquakes, volcanism). In particular, we encourage the submission of trans-disciplinary studies, which integrate observations across a range of spatial and temporal scales to further our understanding of plate tectonics as a planetary process of fundamental importance.

Extreme events and natural hazards are frequent occurrences on our unstable planet. They are predicted to become more common, severe and costly in the future and this session explores their role in human prehistory and history. In order to understand the potential of contemporary and future extreme events to impact human societies, it is critical to understand the mechanisms of how they may have occurred in the past, and elucidate their effects. This session invites contributions from across relevant disciplines. Global in scope and not limited to specific types of extreme events or natural hazards, we hope to compare and contrast differing methods and datasets that address the character and role of extreme events in the human past. Ultimately, we also seek to discuss how the evidence base of Pleistocene and Holocene calamities can be brought into play in the discussion about sustainability and disaster risk reduction in the Anthropocene, as well as to explore how extreme events may have shaped our past.

Smart monitoring and observation systems for hazards, including satellites, seismometers, global networks, uncrewed vehicles (e.g., UAV), and other linked devices, have become increasingly abundant. With these data, we observe our Earth’s restless nature and work towards improving our understanding of hazard processes such as landslides, debris flows, earthquakes, floods, storms, volcanic eruptions, and tsunamis. The large amount of data we have now accumulated with diverse measurements presents an opportunity for earth scientists to employ statistically driven approaches that speed up data processing, improve model forecasts, and give insights into the underlying physical processes. Such big-data approaches are supported by the wider scientific, computational, and statistical research communities who are constantly developing data science and machine learning techniques and software. Hence, data science and machine learning methods are rapidly impacting the fields of geohazards. In this session, we will see research into hazards spanning a broad range of time and spatial scales.

New developments in translation, rotation and strain sensing (such as fibre-optic gyroscopes and fiber-optic cables) enable the complete observation of seismic ground motion and deformation. Applications are manifold, ranging from the reduction of non-uniqueness in seismic inverse problems over the correction of tilt effects to the characterization, separation and reconstruction of the seismic wavefield.

Instrumental developments in ground-motion sensing overlap with considerable improvements in optical and atom interferometry for inertial rotation and gravity sensing which has led to a variety of improved sensor concepts over the last two decades.

We invite all contributions on theoretical advances to the seismic wavefield gradient analysis, on novel measurement techniques, and on all aspects of applications in seismology, geodesy, planetary exploration, gravitational wave detection and fundamental physics.

The vast majority of all telecommunications data (99%) transit through submarine and land-based fibre-optic cables. Global networks of cables encircle the Earth and cover the most remote regions of the continents and oceans. At the same time fibre-optic cables are being used as distributed sensors to measure temperature or strain for a variety of objectives (e.g. fault detect) and environments (e.g. land, marine). Consequently, fibre technologies are becoming a standard tool for crustal exploration and seismic monitoring.

In recent years there have been significant breakthroughs in the use of fibre-optic sensing techniques developed to interrogate cables at very high precision over very large distances both on land and at sea, in boreholes and at the surface. For example, laser reflectometry using DAS (Distributed Acoustic Sensing) on both dedicated experimental and commercial fiber optic cables have successfully detected a variety of signals including microseism, local and teleseismic earthquakes, volcanic events, ocean dynamics, etc. Other laser reflectometry techniques have long been used for the monitoring of large-scale engineering infrastructures (dams, tunnels, bridges, pipelines, etc.). Additionally, fibre-optic technologies have also been applied to natural hazard studies on land (for e.g. monitoring landslides or sinkholes), where in the case of cities, signals of cars can be exploited for exploration, allowing new approaches for urban seismic hazard characterisation.

We welcome contributions that involve the application of fiber-optic cables or sensors in seismology, geodesy, geophysics, natural hazards, oceanography, urban environment, geothermal application, etc. with an emphasis on laboratory studies, large-scale field tests and modelling.

The number and quality of seismic stations and networks continually improves in Europe and worldwide. Current state-of-the-art permanent seismic monitoring means dense deployments of modern broadband velocity and acceleration sensors, often co-located, writing on 24- or 26-bit digitisers, with continuous real-time streaming to data centres. Technological improvements have been accompanied by community developments of standards, protocols, strategies and software to ease and homogenise data acquisition, archival, dissemination and processing. Yet, optimizing performance, improving data and metadata quality, enhancing waveform services and products requires continued efforts by seismic network operators and managers. In this session we welcome contributions from all aspects of seismic network deployment, operation and management. This includes site selection; equipment testing and installation; planning and telemetry; policies for redundancy in data acquisition; processing and archiving; data and metadata QC; data management and dissemination policies; technical and scientific products; integration of different datasets like GPS, OBS and portable arrays.
This session is promoted by the EGU sub-division “Seismic Instrumentation & Infrastructure” and ORFEUS (http://orfeus-eu.org/). ORFEUS coordinates waveform seismology in Europe through the collection, archival and distribution (http://www.orfeus-eu.org/data/eida/; http://www.orfeus-eu.org/data/strong/) of seismic waveform data, metadata and closely-related derived products. This session facilitates seismological data discovery and promotes open data sharing and integration.

The International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBT) senses the solid Earth, the oceans and the atmosphere with a global network of seismic, infrasound, and hydroacoustic sensors as well as detectors for atmospheric radioactivity. The primary purpose of the IMS data is for nuclear explosion monitoring regarding all aspects of detecting, locating and characterizing nuclear explosions and their radioactivity releases. On-site verification technologies apply similar methods on smaller scales as well as geophysical methods such as ground penetrating radar and geomagnetic surveying with the goal of identifying evidence for a nuclear explosion close to ground zero. Papers in this session address advances in the sensor technologies, new and historic data, data collection, data processing and analysis methods and algorithms, uncertainty analysis, machine learning and data mining, experiments and simulations including atmospheric transport modelling. This session also welcomes papers on applications of the IMS and OSI instrumentation data. This covers the use of IMS data for disaster risk reduction such as tsunami early warning, earthquake hazard assessment, volcano ash plume warning, radiological emergencies and climate change related monitoring. The scientific applications of IMS data establish another large range of topics, including acoustic wave propagation in the Earth crust, stratospheric wind fields and gravity waves, global atmospheric circulation patterns, deep ocean temperature profiles and whale migration. The use of IMS data for such purposes returns a benefit with regard to calibration, data analysis methods and performance of the primary mission of monitoring for nuclear explosions.

Geophysical and in-situ measurements of the cryosphere offer important baseline datasets, as well as validation for modelling and remote sensing products. In this session we welcome contributions related to a wide spectrum of methods, including, but not limited to radioglaciology, active and passive seismology, acoustic sounding, Global Navigation Satellite System (GNSS) reflectometry or time delay techniques, cosmic ray neutron sensing, remotely operated vehicle (ROV) or drone applications, geoelectrics, nuclear magnetic resonance (NMR) and methods in radiative transfer (i.e. infrared photography, thermal sounding...).

Contributions could be related to field applications, new approaches in geophysical or in-situ survey techniques, or theoretical advances in data analysis processing or inversion. Case studies from all parts of the cryosphere such as snow and firn, alpine glaciers, ice sheets, glacial and periglacial environments, permafrost, or sea ice, are highly welcome. The focus of the session is to compare experiences in the application, processing, analysis and interpretation of different geophysical and in-situ techniques in these highly complex environments.

This year our session will be a virtual PICO session. The session begins with each presenter giving a “quick fire” 2-minute overview of their research, followed by breakout "rooms" - one per presentation, for authors to further discuss their research. We hope the virtual PICO format will provide as much lively discussion as our normal in-person PICO!

++++++++++++++++++++ Invited Speaker ++++++++++++++++++++

Amy R. Macfarlane: Quasi in-situ snow and sea ice interface microstructure measured by micro-computed tomography

Ambient seismic noise-based monitoring and imaging techniques have matured into a core part of the seismological toolkit. The advantages are based on the commonly obtained robust reconstruction of empirical Green’s function estimates that allows seismic imaging and continuous monitoring of a wide range of subsurface structures.
In this session, we focus on open questions and methodological advances in seismic interferometry and ambient noise based seismology. We invite (A) contributions on new methodological approaches in seismic interferometry and noise processing (B) studies of time variations of elastic material properties and (C) investigations of the sources of the ambient seismic noise.
This could, for example, include contributions that (A) further extend the resolution capabilities and sensitivities of methods using the continuously recorded wavefield and its applications; (B) propose ideas that aim to push the imaging resolution of multiple scattered wavefields; (C) report on case studies of established techniques that are applied to data collected by unconventional solid earth and acoustic acquisition systems such as distributed acoustic sensing cables, rotation sensors, or infrasound installations; (D) investigate causes of temporal variations of medium properties, including suggestions for the upscaling of laboratory configurations to local and regional scales; (E) show monitoring applications that connect the obtained velocity change signals with complementary observables such as seismicity rates, geodetic signals, or meltwater drainage to better constrain underlying physical processes and model parameters; (F) study the excitation of the ambient field over the entire frequency range and implications for the stability of the reconstructed signals.

In the last two decades the number of high quality seismic instruments being installed around the world has grown exponentially and probably will continue to grow in the coming decades. This led to a dramatic increase in the volume of available seismic data and pointed out the limits of the current standard routine seismic analysis, often performed manually by seismologists. Exploiting this massive amount of data is a challenge that can be overcome by using new generation, fully automated and noise-robust seismic processing techniques. In the last years waveform-based detection and location methods have grown in popularity and their application have dramatically improved seismic monitoring capability. Moreover, machine learning techniques, which are dedicated methods for data-intensive applications, are showing promising results in seismicity characterization applications opening new horizons for the development of innovative, fully automated and noise-robust seismic analysis methods. Such techniques are particularly useful when working with data sets characterized by large numbers of weak events with low signal-to-noise ratio, such as those collected in induced seismicity, seismic swarms and volcanic monitoring operations. This session aims on bringing to light new methods and also optimizations of existing approaches that make use of High Performance Computing resources (CPU, GPU) and can be applied to large data sets, either retro-actively or in (near) real-time, to characterize seismicity (i.e. perform detection, location, magnitude and source mechanism estimation) at different scales and in different environments. We thus encourage contributions that demonstrate how the proposed methods help improve our understanding of earthquake and/or volcanic processes.

New models based on seismicity patterns, considering their physical meaning and their statistical significance, shed light on the preparation process of large earthquakes and on the evolution in time and space of clustered seismicity.
Opportunities for improved model testing are being opened by the increasing amount of earthquake data available on local to global scales, together with accurate assessments of the catalogues’ reliability in terms of location precision, magnitude of completeness and coherence in magnitude determination.
Moreover, it is possible to reliably integrate the models with additional information, like geodetic deformation, active fault data, source parameters of previously recorded seismicity, fluid contents, tomographic information, or laboratory and numerical experiments of rock fracture and friction. Such integration allows a detailed description of the system and hopefully an improved forecasting of the future distribution of seismicity in space, time and magnitude.
In this session, we invite researchers to submit their latest results and insights on the physical and statistical models and machine learning approaches for the space, time and magnitude evolution of earthquake sequences. Particular emphasis will be placed on:

• physical and statistical models of earthquake occurrence;
• analysis of earthquake clustering;
• spatial, temporal and magnitude properties of earthquake statistics;
• quantitative testing of earthquake occurrence models;
• reliability of earthquake catalogues;
• time-dependent hazard assessment;
• methods for earthquake forecasting;
• data analyses and requirements for model testing;
• pattern recognition in seismology;
• machine learning applied to seismic data; and
• methods for quantifying uncertainty in pattern recognition and machine learning.

Confirmed solicited speaker: Robert Shcherbakov (University of Western Ontario, London, Ontario, Canada)

This interdisciplinary session welcomes contributions on novel conceptual and/or methodological approaches and methods for the analysis and statistical-dynamical modeling of observational as well as model time series from all geoscientific disciplines.
Methods to be discussed include, but are not limited to linear and nonlinear methods of time series analysis. time-frequency methods, statistical inference for nonlinear time series, including empirical inference of causal linkages from multivariate data, nonlinear statistical decomposition and related techniques for multivariate and spatio-temporal data, nonlinear correlation analysis and synchronisation, surrogate data techniques, filtering approaches and nonlinear methods of noise reduction, artificial intelligence and machine learning based analysis and prediction for univariate and multivariate time series.
Contributions on methodological developments and applications to problems across all geoscientific disciplines are equally encouraged. We particularly aim at fostering a transfer of new methodological data analysis and modeling concepts among different fields of the geosciences.

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Sub-Session "Mathematical Climatology and Space-time Data Analysis" (Abdel Hannachi, Amro Elfeki, Christian Franzke, Muhammad Latif, Carlos Pires)

The recent progress in mathematical methods to solve various problems in weather & climate nonlinear dynamics and data analysis calls for the need to develop a new session that focus on those methods. Novel and powerful mathematical methods have been developed and used in different subjects of climate. Because those methods are used within specific contexts they go unnoticed most of the time by climate researchers. The proposed new session will provide the opportunity to climate scientists and researchers working on developing mathematical methods for climate to come together and present their findings in a transparent way. This will also be easily accessible to other climate scientists who look for, and are interested in specific methods to solve their problems.
Contributions are encouraged from researchers working on mathematical methods and their application to weather and climate. We particularly welcome contributions on optimization, dimension reduction and data mining, space-time patterns identification, machine learning, statistical prediction modelling, nonlinear methods , Bayesian statistics, and Monte-Carlo Markov Chain (MCMC) methods in stochastic modelling.

Tsunamis can produce catastrophic damage on vulnerable coastlines, essentially following major earthquakes, landslides or atmospheric disturbances. After the disastrous tsunamis in 2004 and 2011, tsunami science has grown significantly, opening new fields of research in various domains, and also in regions where the tsunami hazard was previously underestimated.

Tsunamis with the most disastrous impacts at large distances are usually generated following large subduction earthquakes. In this session, the different disciplines used to better understand subduction earthquakes mechanics and quantify the related hazards will be addressed. This includes integrated observations, both seismological and geophysical models, as well as rock physics experiments.

Tsunami hazard can be estimated through numerical modeling, complemented with laboratory experiments. Complete databases are essential to describe past tsunami observations, including both historical events and results of paleotsunami investigations. Furthermore, a robust hazard analysis has to take into account uncertainties and probabilities with the more advanced approaches such as PTHA.
Because the vulnerability of populations, of infrastructures and of the built environment in coastal zones increases, integrated plans for tsunami risk prevention and mitigation should be encouraged in any exposed coastline, consistent with the procedures now in place in a growing number of Tsunami Warning System.
This merged NH5.1/OS4.15/SM4.3 session welcomes multidisciplinary contributions covering any of the aspects mentioned here, encompassing field data, geophysical models, regional hazard studies, observation databases, numerical and experimental modeling, risk studies, real time networks, operational tools and procedures towards a most efficient warning.

Earthquake mechanics is controlled by a spectrum of processes covering a wide range of length scales, from tens of kilometres down to few nanometres. While the geometry of the fault/fracture network and its physical properties control the global stress distribution and the propagation/arrest of the seismic rupture, earthquake nucleation and fault weakening is governed by frictional processes occurring within extremely localized sub-planar slipping zones. The co-seismic rheology of the slipping zones themselves depends on deformation mechanisms and dissipative processes active at the scale of the grain or asperity. The study of such complex multiscale systems requires an interdisciplinary approach spanning from structural geology to seismology, geophysics, petrology, rupture modelling and experimental rock deformation. In this session we aim to convene contributions dealing with different aspects of earthquake mechanics at various depths and scales such as:

· the thermo-hydro-mechanical processes associated with co-seismic fault weakening based on rock deformation experiments, numerical simulations and microstructural studies of fault rocks;
· the study of natural and experimental fault rocks to investigate the nucleation mechanisms of intermediate and deep earthquakes in comparison to their shallow counterparts;
· the elastic, frictional and transport properties of fault rocks from the field (geophysical and hydrogeological data) to the laboratory scale (petrophysical and rock deformation studies);
· the internal architecture of seismogenic fault zones from field structural survey and geophysical investigations;
· the modeling of earthquake ruptures, off-fault dynamic stress fields and long-term mechanical evolution of realistic fault networks;
· the earthquake source energy budget and partitioning between fracture, friction and elastic wave radiation from seismological, theoretical and field observations.
· the interplay between fault geometry and earthquake rupture characteristics from seismological, geodetic, remote sensed or field observations;

We particularly welcome novel observations or innovative approaches to the study of earthquake faulting. Contributions from early career scientists are solicited.

Continental rifting is a complex process spanning from the inception of extension to continental rupture or the formation of a failed rift. This session aims at combining new data, concepts and techniques elucidating the structure and dynamics of rifts and rifted margins. We invite submissions highlighting the time-dependent evolution of processes such as: initiation and growth of faults and ductile shear zones, tectonic and sedimentary history, magma migration, storage and volcanism, lithospheric necking and rift strength loss, influence of the pre-rift lithospheric structure, rift kinematics and plate motion, mantle flow and dynamic topography, as well as break-up and the transition to sea-floor spreading.

We encourage contributions using multi-disciplinary and innovative methods from field geology, geochronology, geochemistry, petrology, seismology, geodesy, marine geophysics, plate reconstruction, or numerical or analogue modelling. Especially welcome are presentations that provide an integrated picture by combining results from active rifts, passive margins, failed rift arms or by bridging the temporal and spatial scales associated with rifting.

Withing this session, a specific segment will be dedicated to studies of rift tectonics in the The Afro-Arabian rift system (the basins of the Gulf of Suez, Gulf of Aqaba, Red Sea, Gulf of Aden, Afar depression and the surrounding regions or related areas). This system contains the world’s largest active continental rift and is the key locality for studying continental breakup processes. Natural phenomena such as basin formation, continental breakup, seismic and volcanic activity, and the formation of mineral resources in and around the three arms of the Afar triple junction highlights some of the key aspects of this complex rift system.

The geological processes that we infer from observations of the Earth’s surface, together with the landscape features are direct consequences of the dynamic Earth, and in particular, of the interaction between tectonic plates. Seismological studies are key for unraveling the present structure and fabric of the lithosphere and the asthenosphere. However, interdisciplinary work is required to fully understand the underlying processes and how features such as anisotropies in the crust, lithospheric mantle or the asthenosphere evolved through time and how they are related. Here we want to gather those studies focusing on seismic anisotropy and deformation patterns that can successfully improve our knowledge of the processes, leading to the observed present geometries (of the crust and the upper mantle). The main goal of the session is to establish closer links between seismological observations and process-oriented modelling studies to demonstrate the potential of different methods, and to share ideas of how we can collaboratively study upper mantle structure, and how the present-day fabrics of the lithosphere relates to the contemporary deformation processes and ongoing dynamics within the asthenospheric mantle.
Contributions from studies employing seismic anisotropy observations, tomography and waveform modeling, geodetic data, numerical and analogue modelling are welcome.

We invite, in particular multidisciplinary, contributions which focus on the structure and evolution of the continental crust and upper mantle and on the nature of mantle discontinuities. The latter include, but are not limited to, the mid-lithosphere discontinuity (MLD), the lithosphere-asthenosphere boundary (LAB), and the mantle transition zone, as imaged by various seismological techniques and interpreted within interdisciplinary approaches. Papers with focus on the structure of the crust and the nature of the Moho are also welcome. Methodologically, the contributions will include studies based on seismic, thermal, gravity, petrological, and/or electro-magnetic data interpretations.

Invited presentations by
Irina M. Artemieva (Augustus Love Medal Lecture) and
Shun-Ichiro Karato

Slip at faults generate ground motion over a wide range of time-scales, from milliseconds to decades and centuries. While geodesy and seismology have been used independently in the past to study the fault behavior, new capabilities in space geodesy as well as seismology analysis argue for a further integration of both disciplines. A non-limitative list of progresses include the development of continuous GNSS networks allowing to monitor motion over a frequency bandwidth overlapping with seismology, new radar satellite missions, optic imaging capabilities allowing to capture new signals, before, during and after earthquakes, new detection techniques of seismic signal and the ability to build high quality earthquakes, tremors and low-frequency earthquakes catalogues, opening new prospects for the study of the Earth’deformation and earthquakes.

This session will gather colleagues interested in integrating seismological and geodetic observations, data, and analysis to better understand the Earth’s deformation and earthquakes. Welcome are contributions about new technologies aiming at improving our ability to monitor ground motion at various time-scales inland and offshore at the sea-floor.
Comparison, validation and dissemination of high-quality accessible data and software are also encouraged. Finally, we encourage submission of joint analysis integrating seismology and geodesy to better understand earthquakes from regional to local approaches. Detection and characterization of transient slip through their joint geodetic and seismic signatures are most welcome.

This session is proposed by the joint IAG-IASPEI Seismo-geodesy sub-commission.

On 29 December 2020, a major earthquake (Mw 6.4) occurred in Croatia close to Petrinja, only nine months after another Mw 5.5 damaging earthquake in Zagreb, the capital city located 45 km north of Petrinja. The December shock is the strongest event in continental Europe since the Norcia sequence (Italy) in 2016 and was caused by the rupture of a NW-SE dextral strike-slip fault at the boundary between the Dinarides and the Pannonian basin ; it was preceded by two strong foreshocks (M~5) the day before. Seismic shaking was widely felt across Europe, and caused extensive damage to buildings and infrastructures in the epicentral region. The earthquake resulted in liquefaction over large areas, and many cracks and a surface rupture have been observed in the field.
This late-breaking session aims at gathering contributions to discuss the 2020 Petrinja earthquake sequence, its surface effects on human and natural environment in terms of shaking and faulting. We encourage presentations dealing with the seismological, geodetical or geological observations related to this earthquake and the ongoing seismic sequence, as well as insights on the regional faults, their historical seismicity or recent geological activity. All this together can help in understanding the geodynamics of this seismically active but poorly characterized region.

This session will cover applied and theoretical aspects of geophysical imaging, modelling and inversion using active- and passive-source seismic measurements as well as other geophysical techniques (e.g., gravity, magnetic and electromagnetic) to investigate properties of the Earth’s crust and uppermost mantle, and explore the processes involved. We invite contributions focused on methodological developments, theoretical aspects, and applications. Studies across the scales and disciplines are particularly welcome.

Among others, the session may cover the following topics:
- Active- and passive-source imaging using body- and surface-waves;
- Full waveform inversion developments and applications;
- Advancements and case studies in 2D and 3D imaging;
- Interferometry and Marchenko imaging;
- Seismic attenuation and anisotropy;
- Developments and applications of multi-scale and multi-parameter inversion; and,
- Joint inversion of seismic and complementary geophysical data.

Geophysical imaging techniques are widely used to characterize structures and processes in the shallow subsurface. Methods include active imaging using seismic, (complex) electrical resistivity, electromagnetic, and ground-penetrating radar methods, as well as passive monitoring based on ambient noise or electrical self-potentials. Advances in experimental design, instrumentation, data acquisition, data processing, numerical modeling, and inversion constantly push the limits of spatial and temporal resolution. Despite these advances, the interpretation of geophysical images often remains ambiguous. Persistent challenges addressed in this session include optimal data acquisition strategies, (automated) data processing and error quantification, appropriate spatial and temporal regularization of model parameters, integration of non-geophysical measurements and geological realism into the imaging process, joint inversion, as well as the quantitative interpretation of tomograms through suitable petrophysical relations.

In light of these topics, we invite submissions concerning a broad spectrum of near-surface geophysical imaging methods and applications at different spatial and temporal scales. Novel developments in the combination of complementary measurement methods, machine learning, and process-monitoring applications are particularly welcome.

Invited speaker: Burke Minsley (USGS)

In recent years, the application of shear-wave seismic methods for shallow investigations (< 500 m depth) has become more and more popular. Shear waves are utilized for structural imaging, geotechnical investigations, and elastic parameter analysis. Methods using shear waves comprise, e.g., reflection imaging, tomography, and full waveform inversion.
Shear-wave imaging has great potential for shallow studies. For instance, near-surface resolution profits from low shear-wave velocities. Especially, shear wave reflection signals can be detected at small offsets compared to P-waves, which makes shear-wave reflection surveying cost efficient.
Shear-wave surveys can profit from sealed ground conditions due to the suppression of Lovewaves, and, thus, are predesignated for urban areas. But shallow shear-wave and multicomponent seismic requires a continuous technical development of specialized sources and customized equipment and makes innovative concepts for acquisition and data processing necessary (e.g. interferometry, full waveform inversion, converted waves).
Exciting as well as recording several components of the ground motion simultaneously is further beneficial, since it allows separating vertically (SV) and horizontally (SH) polarized shear wavefields, which is mandatory for 3-D surveys. Wave conversion and scattering effects can be distinguished, and differently polarised shear waves simplify the detection of seismic anisotropy. This session promotes the exchange of experience using shear waves in shallow applications and triggers discussions about their potential in seismic imaging. Combined studies using P- and shear waves are a plus. With the focus on shear waves, we invite, but do not restrict, contributions to technical development, data analysis, seismic processing, and case studies. The latter may comprise, e.g., (a) geotechnical studies, such as examination of soil rigidity, (b) exploration of structures, such as volcanic craters or groundwater resources, (c) analysis of neotectonics, active faults, quick clays, landslides, sinkholes, and subrosion structures, and (d) more exotic applications, such as the exploration of glacier ice thickness.

Major advances on imaging subsurface structures have been made in recent years thanks to 3D seismic exploration, tomography, numerical and forward modelling techniques. However, significant problems, and ambiguities in geological interpretation of subsurface data still remain. This session seeks contributions directly related to the practice of interpretation of the Earth's subsurface tectonic structure using subsurface imaging techniques but also combining geophysical geological observations with numerical modelling approaches. The session will address problems related to deep tectonic features, fault structure, fluid-rock interactions using time lapse imaging, storage structure and more generally basin and tectonic analysis. Contributions may include submissions that advance geophysical or geological concepts and principles of seismic interpretation; correlation with and calibration by geological and engineering data; case studies; algorithms for interpretation; image processing and forward modelling techniques. Contributions that describe interpretation methods and applications involving an integration of multiple datasets to quantify as well as visualize subsurface structure are strongly encouraged. Presentations that focus on the large scale structure , basin exploration , CO2 sequestration, and extraction of mineral resources, using seismic datasets, and coupled to geological observations with numerical experiments are welcomed.

Our understanding of the iron cores in Earth and other bodies is progressing rapidly thanks to cross-fertilization between a number of observational, theoretical and experimental disciplines.

Improved seismic observations continue to provide better images and prompt refinements in structural and geodynamic models. Mineral physics provides constraints for dynamic, structural, and thermodynamic models. Improved constraints on the core heat budget, paleomagnetic observations of long-term magnetic field variations, and high-resolution numerical simulations promote the exploration of new dynamo mechanisms. Geomagnetic observations from both ground and satellite, along with magneto-hydrodynamic experiments, provide additional insight to our ever expanding view of planetary cores.

This session welcomes contributions from all disciplines, as well as interdisciplinary efforts, on attempts to proceed towards an integrated, self-consistent picture of planetary core structure, dynamics and history, and to understand their overwhelming complexity.

Many regions of the Earth, from crust to core, exhibit anisotropic fabrics which can reveal much about geodynamic processes in the subsurface. These fabrics can exist at a variety of scales, from crystallographic orientations to regional structure alignments. In the past few decades, a tremendous body of multidisciplinary research has been dedicated to characterizing anisotropy in the solid Earth and understanding its geodynamical implications. This has included work in fields such as: (1) geophysics, to make in situ observations and construct models of anisotropic properties at a range of depths; (2) mineral physics, to explain the cause of some of these observations; and (3) numerical modelling, to relate the inferred fabrics to regional stress and flow regimes and, thus, geodynamic processes in the Earth. The study of anisotropy in the Solid Earth encompasses topics so diverse that it often appears fragmented according to regions of interest, e.g., the upper or lower crust, oceanic lithosphere, continental lithosphere, cratons, subduction zones, D'', or the inner core. The aim of this session is to bring together scientists working on different aspects of anisotropy to provide a comprehensive overview of the field. We encourage contributions from all disciplines of the earth sciences (including mineral physics, seismology, magnetotellurics, geodynamic modelling) focused on anisotropy at all scales and depths within the Earth.

Seismic techniques are becoming widely used to detect and quantitatively characterise a wide variety of natural processes occurring at the Earth’s surface. These processes include mass movements such as landslides, rock falls, debris flows and lahars; glacial phenomena such as icequakes, glacier calving/serac falls, glacier melt and supra- to sub-glacial hydrology; snow avalanches; water storage and water dynamics phenomena such as water table changes, river flow turbulence and fluvial sediment transport. Where other methods often provide limited spatial and temporal coverage, seismic observations allow recovering sequences of events with high temporal resolution and over large areas. These observational capabilities allow establishing connections with meteorological drivers, and give unprecedented insights on the underlying physics of the various Earth’s surface processes as well as on their interactions (chains of events). These capabilities are also of first interest for real time hazards monitoring and early warning purposes. In particular, seismic monitoring techniques can provide relevant information on the dynamics of flows and unstable slopes, and thus allow for the identification of precursory patterns of hazardous events and timely warning.

This session aims at bringing together scientists who use seismic methods to study Earth surface dynamics. We invite contributions from the field of geomorphology, cryospheric sciences, seismology, natural hazards, volcanology, soil system sciences and hydrology. Theoretical, field based and experimental approaches are highly welcome.

Solicited presenter: Kate Allstadt - USGS Geologic Hazards Science Center, Golden, CO, USA

Earthquake swarms are characterized by a complex temporal evolution and a delayed occurrence of the largest magnitude event. In addition, seismicity often manifests with intense foreshock activity or develops in more complex sequences where doublets or triplets of large comparable magnitude earthquakes occur. The difference between earthquake swarms and these complex sequences is subtle and usually flagged as such only a posteriori. This complexity derives from aseismic transient forcing acting on top of the long-term tectonic loading: pressurization of crustal fluids, slow-slip and creeping events, and at volcanoes, magmatic processes (i.e. dike and sill intrusions or magma degassing). From an observational standpoint, these complex sequences in volcanic and tectonic regions share many similarities: seismicity rate fluctuations, earthquakes migration, and activation of large seismogenic volume despite the usual small seismic moment released. The underlying mechanisms are local increases of the pore-pressure, loading/stressing rate due to aseismic processes (creeping, slow slip events), magma-induced stress changes, earthquake-earthquake interaction via static stress transfer or a combination of those. Yet, the physics behind such processes and the ultimate reasons for the occurrence of swarm-like rather than mainshock-aftershocks sequences, is still far beyond a full understanding.

This session aims at putting together studies of swarms and complex seismic sequences driven by aseismic transients in order to enhance our insights on the physics of such processes. Contributions focusing on the characterization of these sequences in terms of spatial and temporal evolution, scaling properties, and insight on the triggering physical processes are welcome. Multidisciplinary studies using observation complementary to seismological data, such as fluid geochemistry, deformation, and geology are also welcome, as well as laboratory and numerical modeling simulating the mechanical condition yielding to swarm-like and complex seismic sequences.

Numerous cases of induced/triggered seismicity resulting either directly or indirectly from injection/extraction associated with anthropogenic activity related to geo-resources exploration have been reported in the last decades. Induced earthquakes felt by the general public can often negatively affect public perception of geo-energies and may lead to the cancellation of important projects. Furthermore, large earthquakes may jeopardize wellbore stability and damage surface infrastructure. Thus, monitoring and modeling processes leading to fault slip, either seismic or aseismic, are critical to developing effective and reliable forecasting methodologies during deep underground exploitation. The complex interaction between injected fluids, subsurface geology, stress interactions, and resulting fault slip requires an interdisciplinary approach to understand the triggering mechanisms, and may require taking coupled thermo-hydro-mechanical-chemical processes into account.
In this session, we invite contributions from research aimed at investigating the interaction of the above processes during exploitation of underground resources, including hydrocarbon extraction, wastewater disposal, geothermal energy exploitation, hydraulic fracturing, gas storage and production, mining, and reservoir impoundment for hydro-energy. We particularly encourage novel contributions based on laboratory and underground near-fault experiments, numerical modeling, the spatio-temporal relationship between seismic properties, injection/extraction parameters, and/or geology, and fieldwork. Contributions covering both theoretical and experimental aspects of induced and triggered seismicity at multiple spatial and temporal scales are welcome.

Over the past few years, major technological advances allowed to significantly increase both the spatial coverage and frequency bandwidth of multi-disciplinary observations at active volcanoes. Networks of instruments for the quantitative measurement of many parameters now permit an unprecedented, multi-parameter vision of the surface manifestations of mass transport beneath volcanoes. Furthermore, new models and processing techniques have led to innovative paradigms for inverting observational data to image the structures and interpret the dynamics of volcanoes. Within this context, this session aims at bringing together a multidisciplinary audience to discuss the most recent innovations in volcano imaging and monitoring, and to present observations, methods and models that increase our understanding of volcanic processes. New attention has recently been paid to quiescent volcanoes since multidisciplinary investigations showed that magma accumulation at depth can contribute to degassing of volatiles for a long time after the last activity, highlighting the risk of reactivation after a long phase of inactivity. Furthermore, mantle degassing and magma accumulation in continental regions far from volcanism might play an active role in seismicity.
We welcome contributions (1) related to methodological and instrumental advances in geophysical, geological and geochemical imaging of volcanoes, and (2) to explore new knowledge provided by these studies on the internal structure and physical processes of volcanic systems.
We invite contributors from all geophysical, geological and geochemical disciplines such as seismology, electromagnetics, geoelectrics, gravimetry, magnetics, muon tomography, volatile measurements and analysis; from in-situ monitoring networks to high resolution remote sensing and innovative processing methods, applied to volcanic systems ranging from near-surface hydrothermal activity to magmatic processes at depth. We hope in this way to highlight the scientific advances available through the combination of these complementary research areas and to encourage future collaborative efforts.

Vetted probabilistic earthquake forecasts can contribute to more earthquake-resilient societies. Forecasts underpin seismic hazard assessments and thus determine building and life safety. They also provide scientifically sound information about the time-dependence of earthquake potential before, during and after earthquake sequences. To ensure forecasts are trustworthy and to assess the scientific hypotheses underlying the forecasts, models should be tested both retrospectively and prospectively (i.e., against yet-to-be-collected data). For this purpose, the Collaboratory for the Study of Earthquake Predictability (CSEP) provides tools and methods for testing the consistency and precision of earthquake forecasts. This session welcomes contributions that showcase advances in the science of earthquake forecasting and model testing. These can include: new approaches for identifying precursory activity (e.g. b-value variations, aseismic slip transients); forecasts based on empirical machine-learning or physical stress-transfer algorithms; applications of models to earthquake sequences around the globe; advances in model evaluation techniques; or contributions to software tools for model developers. Presentations may also highlight progress of community efforts, such as the EU H2020 project RISE (Real-time earthquake rIsk reduction for a reSilient Europe, www.rise-eu.org) and other initiatives.

From the real-time integration of multi-parametric observations is expected the major contribution to the development of operational t-DASH systems suitable for supporting decision makers with continuously updated seismic hazard scenarios. A very preliminary step in this direction is the identification of those parameters (seismological, chemical, physical, biological, etc.) whose space-time dynamics and/or anomalous variability can be, to some extent, associated with the complex process of preparation of major earthquakes.
This session wants then to encourage studies devoted to demonstrate the added value of the introduction of specific, observations and/or data analysis methods within the t-DASH and StEF perspectives. Therefore, studies based on long-term data analyses, including different conditions of seismic activity, are particularly encouraged. Similarly welcome will be the presentation of infrastructures devoted to maintain and further develop our present observational capabilities of earthquake related phenomena also contributing in this way to build a global multi-parametric Earthquakes Observing System (EQuOS) to complement the existing GEOSS initiative.
To this aim this session is not addressed just to seismology and natural hazards scientists but also to geologist, atmospheric sciences and electromagnetism researchers, whose collaboration is particular important for fully understand mechanisms of earthquake preparation and their possible relation with other measurable quantities. For this reason, all contributions devoted to the description of genetic models of earthquake’s precursory phenomena are equally welcome.

Seismic hazard assessment in regions of low lithospheric strain rely on a global-analogues approach for parameterizing seismic hazard models. In this approach, seismicity rate and earthquake recurrence distributions are generated by amalgamating aerial source zones with limited seismicity data or by drawing on more far‐field analogue regions of slow lithospheric strain. The premise is that regions of low lithospheric strain have the same seismogenic potential. This session seeks to discuss new insights into this premise.

We invite contributions that (1) present new observations that place constraints on earthquake occurrence in low-strain regions, (2) explore patterns of stable or temporally varying earthquake occurrence, and (3) provide insight into the mechanisms that control earthquakes in regions of slow deformation via observation and/or modeling.

These contributions cover two different research components. The first component calls upon researchers with recently developed paleoseismic, geomorphic, geodetic, geophysical, and seismologic datasets that provide insight into the earthquake cycle in low-strain settings. The second component includes contributions that more broadly synthesize recent insights into the seismotectonics of low strain regions and/or explore the driving mechanisms for earthquakes in these regions. Collectively, these contributions provide a current view of the global-analogues premise.

Earthquake disaster mitigation involves different elements, ranging from analysis of hazards (e.g. physical description of ground shaking) to its impact on built and natural environment, from vulnerability and exposure to hazards to capacity building and resilience, from long-term preparedness to post-event response. The scientific base of this process involves various seismic hazard/risk models, developed at different time scales and by different methods, as well as the use of heterogeneous observations and multi-disciplinary information. Accordingly, we welcome contributions about different types of seismic hazards research and assessments, both methodological and practical, and their applications to disaster risk reduction in terms of physical and social vulnerability, capacity and resilience.
This session aims to tackle theoretical and implementation issues, as well as aspects of communication and science policy, which are all essential elements towards effective disasters mitigation, and include:
⇒ earthquake hazard and risk estimation at different time and space scales, including their performance verification against observations (including unconventional seismological observations);
⇒ time-dependent seismic hazard and risk assessments (including contribution of aftershocks), and post-event information (early warning, alerts) for emergency management;
⇒ earthquake-induced cascading effects (e.g. landslides, tsunamis, etc) and multi-risk assessment (e.g. earthquake plus flooding).
Different hazards can combine and mutually enhance their impact, turning into a disaster. The COVID-19 pandemic pointed out the low preparedness of human society to large-scale crises. In particular, there have been several damaging earthquakes during the pandemic (Croatia, Greece, USA, Iran), which highlighted the impacts of concurrent hazards and the complexity in handling such situations.
The interdisciplinary session will provide an opportunity to share lessons learned from recent events, best practices and experience gained with different methods, providing opportunities to advance our understanding of disaster risk in "all its dimensions of vulnerability, capacity, exposure of persons and assets, hazard characteristics and the environment", while simultaneously highlighting existing gaps and future research directions.

Innovative forward and inverse modeling techniques, advances in numerical solvers and the ever-increasing power of high-performance compute clusters have driven recent developments in inverting seismic and other geophysical data to reveal properties of the Earth at all scales.

This session provides a forum to present, discuss and learn the state-of-the-art as well as future directions in seismic tomography, computational inverse problems, and uncertainty quantification.

We welcome contributions focusing on, but not limited to:

- innovative modeling techniques and advancements in numerical solvers,
- seismic tomography and full-waveform inversion from local to global scales,
- multi-scale, multi-parameter and joint inversions of Earth structure and sources,
- statistical inverse problems and uncertainty quantification,
- homogenization and effective medium theory,
- machine learning algorithms for seismic problems,
- big data (seismic & computational) problems on emerging HPC architectures.

Numerical modeling of earthquakes provides new approaches to apprehend the physics of earthquake rupture and the seismic cycle, seismic wave propagation, fault zone evolution and seismic hazard assessment.
Recent advances in numerical algorithms and increasing computational power enable unforeseen precision and multi-physics components in physics-based earthquake simulation but also pose challenges in terms of fully exploiting modern supercomputing infrastructure, realistic parameterization of simulation ingredients and the analysis of large synthetic datasets while advances in laboratory experiments link earthquake source processes to rock mechanics.
This session aims to bring together modelers and data analysts interested in the physics and computational aspects of earthquake phenomena and earthquake engineering. We welcome studies focusing on all aspects of seismic hazard assessment and the physics of earthquakes - from slow slip events, fault mechanics and rupture dynamics, to wave propagation and ground motion analysis, to the seismic cycle and inter seismic deformation - and studies which further the state-of-the art in the related computational and numerical aspects.