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.
This session aims to bring together modelers and data analysts interested in the physics and computational aspects of earthquake phenomena. We welcome studies focusing on all aspects of the physics of various 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.
We further encourage studies linking earthquake source processes to rock mechanics and the laboratory scale.
Earthquake Source Processes: Recent Advances in Observation, Imaging, and Modeling
This session covers the broad field of earthquake source processes, and includes the topics of observing the surface deformation caused by earthquakes, imaging the rupture kinematics and simulating earthquake dynamics using numerical methods, to develop a deeper understanding of earthquake source physics. We also invite presentation that link novel field observations and laboratory experiments to earthquake dynamics, and studies on earthquake scaling properties. Of particular interest are innovative studies on quantifying the uncertainties in earthquake source-parameter estimation.
Within this framework our session also provides a forum to discuss case studies of field observation, kinematic and dynamic source modeling of recent significant earthquakes.
Earthquake foreshocks: identification, observation, modeling, and lessons to be learned
Over the past several years, interest in earthquake foreshocks has experienced considerable growth. This can, on one side, be explained by a largely improved observational database that spans all seismic scales. A development that is driven by a growing number of permanent seismic stations and large-scale campaign networks, the development of advanced detection and analysis techniques, and by the improvement of laboratory equipment and techniques. In addition, the ongoing endeavor to better understand induced seismicity has been contributing to this upgrowth with densely-monitored underground lab-scale experiments and enhanced microseismic monitoring. On the other side, earthquake foreshocks are widely perceived as one of the few and, as of now, most direct observations of earthquake nucleation processes.
Foreshocks are generally thought to arise by one of two mechanisms: cascading failure or preslip. The cascading model proposes that a mainshock following a foreshock has an identical origin to that of aftershocks. In this case, earthquake frequency-magnitude statistics predict that occasionally an aftershock will be larger than the prior event, which makes the prior event a foreshock only after the fact. The mechanism proposed by the preslip model is that premonitory processes - perhaps fault creep related to mainshock nucleation - result in stress changes that drive the foreshock process. Seismologists have found no agreement so far; this is made more difficult by two facts: that no agreed-upon, universal strategy to identify foreshocks in a seismic catalog exists and that data quality and quantity vary considerably over spatial and temporal scales.
In this session, we want to bring together scientists from all disciplines working on, or interested in, earthquake foreshock occurrence. We invite reports on observational and theoretical studies on all scales. This includes laboratory and deep underground experimental earthquakes, as well as microseismic to megathrust earthquakes. We also encourage submissions from colleagues working on advanced detection and analysis techniques for improved foreshock identification.
Understanding large subduction earthquakes and tsunamigenesis by integrating geological and geophysical observations, laboratory results, and numerical modeling
Since 2004, there have been a number of large subduction earthquakes whose unexpected rupture features contributed to the generation of devastating tsunamis. The impact that these events had on human society highlights the need to improve our knowledge of the key mechanisms behind their origin. Advances in these areas have led to progess in our understanding of the most important parameters affecting tsunamigenesis. For example, unexpectedly large slip was observed during the 2011 Tohoku-Oki earthquake, leading to re-investigations of the geology of other subduction zones and the conditions that can lead to large slip at the trench.
In general, the large amount of geophysical data recorded at present has led to new descriptions of faulting and rupture complexity (e.g., spatial and temporal seismic rupture heterogeneity, fault roughness, geometry and sediment type, interseismic coupling, etc.). Rock physicists have proposed new constitutive laws and parameters based on a new generation of laboratory experiments, which simulate close to natural seismic deformation conditions on natural fault samples. Analog modellers now have apparati that simulate multiple seismic cycles with unprecedented realism. These represent a valuable tool for investigating how various boundary conditions (e.g., frictional segmentation, interplate roughness) influence the seismic behavior of subduction megathrusts. In addition, advances in numerical modelling now allow scientists to test how new geophysical observations, e.g. from ocean drilling projects and laboratory analyses, influence subduction zone processes over a range of temporal and spatial scales (i.e., geodynamic, seismic cycling, earthquake rupture, wave propagation modelling).
In light of these advances, this session has a twofold mission: i) to integrate recent results from different fields to foster a comprehensive understanding of the key parameters controlling the physics of large subduction earthquakes over a range of spatial and temporal scales; ii) to individuate how the tsunami hazard analysis can benefit from using a multi-disciplinary approach.
We invite abstracts that enhance interdisciplinary collaboration and integrate observations, rock physics experiments, analog- and numerical modeling, and tsunami hazard.
The Mechanics of Faulting from shallow to deep earthquakes: Interplay between multiple length scales.
The mechanics of earthquakes is controlled by a spectrum of processes covering a wide range of length scales, from tens of kilometres down to few nanometres. For instance, 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. If this is the case of shallow earthquakes, the nucleation of intermediate and deep earthquakes remains enigmatic since it occurs at elevated ambient pressure-temperature conditions which should favour plastic deformation and suppress frictional processes. Though, recent studies on fault rocks of Earth’s lower crust and upper mantle reveal microstructures comparable to those associated with co-seismic slip and off-fault damage in brittle rocks. 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 to 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 (e.g. seismic, electric and electromagnetic methods);
· 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 (e.g. coseismic slip and rupture velocity distribution) 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.
Solicited oral presentation: Matthew Tarling (University of Otago)
From Oceanic to Continental Subductions: tectonics and earthquakes
Many new high quality and high resolution geophysical and geological data had been acquired in the past years that need to be updated, re-analysed and re-interpreted in the light of our present knowledge in subductions processes. Moreover it is needed to better clarify the temporal and spatial evolution of those processes in order to much precise our geodynamic ideas of mountain building, subduction, transition of collision to subduction, or transition of subduction to collision.
Among other global places, the zone from Japan, Taiwan to the Philippines is a key area to study such subduction/collision transition due to the rapid convergence between Eurasian and Philippine Sea plates. There are geodynamic inversion of the east dipping Manila oceanic subduction, that evolves northward, first, into a Continental Subduction (also called Collision) onshore Taiwan, then secondly, east of Taiwan, into the north dipping Ryukyu arc/continent subduction. Due to the so rapid Plates shortening rate (10cm.y-1), those active Oceanic to Continental Subductions processes in Taiwan creates 1/8 of the annual seismicity in the World !
There are other places in the World active or not, that should also be taken into careful consideration in order to reveal and lead us to better understand new tectonic processes (e.g.: Alpes, Pyrénées, Cascades and so on).
To conclude in this EGU session, we aim to update the existing geodynamic state of the art of the oceanic to continental subductions processes after so numerous data that had been collected recently and all the works that had been done on this subject. Therefore this EGU Session should help us to much better understand the tectonics related to plate, plate collision and the transition between the subduction and collision.
Crust-Lithosphere-Asthenosphere Interplay, Deformation and Dynamics
Knowledge of the lithosphere-asthenosphere system and its dynamics is one of the key questions for understanding geological processes. Constraints on the style, mechanism, and pattern of deformation in the crust and upper mantle come from direct and indirect observations using a variety of methods. Seismological studies focusing on anisotropy have successfully improved our knowledge of deformation patterns, and when combined with tomographic models, anisotropy can shed light on the geometry of deformation in the lithosphere and asthenosphere. Sophisticated geodynamic modeling (numerical and physical analogue) and laboratory (rock physics) experiments enhance our understanding of flow patterns in the Earth’s upper mantle and their bearing on vertical motions of crust and lithosphere. Combined with seismic anisotropy data these methods have the potential to reveal the mechanisms that create deformation-induced features such as shape preferred orientation (SPO) and lattice-preferred orientation (LPO). Structural and kinematic characterization of deformation events by geometric and kinematic analyses infer the direction and magnitude of the tectonic forces involved in driving deformation within crust and upper mantle. Additionally, physical analogue and numerical modeling studies have fostered our understanding of complex 3D-plate interaction on various time-scales, regulated through the degree of plate coupling and the rheology of the lithosphere.
However, more work is required to better integrate the various experimental and modelling techniques and to link them to multi-scale observations. This session will bring together different disciplines that focus on the deformation of the lithosphere and upper mantle as well as on the dynamics and nature of the lithosphere-asthenosphere system. The main goal is to demonstrate the potential of different methods, and to share ideas of how we can collaboratively study lithospheric deformation, and how it relates to the ongoing dynamics within the asthenospheric mantle. Contributions are sought from studies employing seismic observation, geodynamical modeling (analogue and numerical), structural geology, and mineral and rock physics.
Greg Houseman (Institute of Geophysics and Tectonics, University of Leeds)
Agnes Kiraly (Department of Geosciences, University of Oslo)
Earthquakes: from slow to fast, from the field to the laboratory and models.
The advent of novel technologies have boosted our capability of acquiring new evidences that faults behavior is various and extremely sensitive to a large number of parameters. These evidences are supported in natural earthquakes by the occurence of a large pletora of events spanning from slow to fast earthquakes, precursory slips, non volcanic tremors and low frequency earthquakes. The aim of this session is to convey interdisciplinary studies on fault behaviour and processes controlling the propagation of slip instabilities in rocks, granular materials and/or laboratory analogs; we invite contributions at the frontiers between Rock Mechanics, Models, Seismology, Tectonics and Mineralogy dealing with either slow, fast or transient evolution of earthquakes and earthquake sequences in shallow and deep environments; we welcome studies performed at the laboratory and field scale, providing insights on earthquake evolution and/or constraining observed seismological statistical laws like Omori’s and Gutenberg-Richter’s; we welcome innovative techniques that help the observations and take advantage of high-speed imaging and continuous acoustic emission streaming data.
Earthquakes, active tectonics, and seismic hazard in regions of slow lithospheric deformation
Earthquakes that occur within regions of slow lithospheric deformation (low-strain regions) are inherently difficult to study. The long interval between earthquakes, coupled with natural and anthropogenic modification, limit preservation of paleoearthquakes in the landscape. Low deformation rates push the limits of modern geodetic observation techniques. The short instrumental record challenges extrapolation of small earthquake recurrence based on modern seismological measurement to characterize the probability of larger, more damaging earthquakes. Characterizing the earthquake cycle in low-strain settings is further compounded by temporal clustering of earthquakes, punctuated by long periods of quiescence (e.g. non-steady recurrence intervals). However, earthquakes in slowly deforming regions can reach high magnitudes and pose significant risk to populations.
This session seeks to integrate paleoseismic, geomorphic, geodetic, geophysical, and seismologic datasets to provide a comprehensive understanding of the earthquake cycle in low-strain regions. This session will draw upon recent advances in high-resolution topography, geochronology, satellite geodesy techniques, subsurface imaging techniques, longer seismological records, high-density geophysical networks and unprecedented computational power to explore the driving mechanisms for earthquakes in low-strain settings. We welcome 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 recurrence, and (3) provide insight into the mechanisms that control earthquakes in regions of slow deformation via observation and/or modeling.