Induced and Triggered Seismic Activity: Observation, Theory and Hazard Analysis
Induced and triggered seismicity are common phenomena associated with sub-surface exploration and remote seismic events, respectively, and have been related to hydrocarbon extraction, hydraulic fracturing, geothermal exploitation, open-pit crater formation and underground mining operations, CO2 sequestration, and filling of new water reservoirs. Public awareness and concern of induced seismicity has become ubiquitous in locations where subsurface exploration and storage is carried out in close proximity to communities. Of particular concerns are massive fluid injections for hydro-fracturing to increase subsurface permeability as well as long-term injection in disposal wells. These concerns have led to regulations to passively monitor induced seismicity and consequently to a wealth of continuous seismic data. In contrast to the increase in data volume, our understanding of the relationship between exploitation techniques and induced seismicity as well as earthquake-earthquake interactions is still limited. New processing methods to analyze data and quantitative models to improve our understanding of the causal relationship between exploitation and seismicity have been developped. The current session is intended to provide a platform to present the latest research, field studies, theoretical and modelling aspects as well as methods for seismic hazard analysis related to induced and triggered seismicity. Topics to be presented include spatio-temporal variations of physical parameters in reservoirs and natural environments including stress and pressure changes, spatial-temporal patterns of seismicity, source mechanisms of micro- or larger-scale seismicity, mechanisms for induced events and seismic interaction, as well as, fracture-induced anisotropy. Contributions are sought from fundamental and applied research covering the fields of oil and gas operations including hydro-fracturing, geothermal exploitation particularly related to enhanced geothermal systems, open pit and underground mining, CO2 storage, and other fields such as volcano-seismology where induced and triggered seismic activity is observed.
Seismic sources, signals and structural imaging on volcanoes: observations and modelling
Volcanic seismicity is fundamental for monitoring and investigating volcanic systems, their structure and processes that occur therein. Volcanoes are very complex objects, where both the pronounced heterogeneity and topography can modify the recorded signals to a great extent. In source inversion work, one of the challenges is to capture the effect of small scale heterogeneities in order to remove complex path effects from seismic data. This requires high resolution imagery, which is a significant challenge in heterogeneous volcanoes. If not removed, the path effect signature may significantly alter our interpretation of the seismic source location and mechanism. In addition, the link between the variety of physical processes beneath volcanoes and their seismic response (or lack of) is often not well known, leading to large uncertainties in the interpretation of volcano dynamics based on the seismic observations. Taking into account all these complexities, many standard techniques for seismic analysis may fail to produce breakthrough results.
In order to address the outlined challenges, this session aims to bring together seismologists, volcano and geothermal seismologists, wave propagation and source modellers, working on different aspects of volcano seismology including: (i) seismicity catalogues, statistics & spatio-temporal evolution of seismicity, (ii) seismic wave propagation & scattering, (iii) new developments in volcano imagery, (iii) seismic source inversions, and (iv) seismic time-lapse monitoring. Contribution on controlled geothermal systems in volcanic environments are also welcome.
By considering interrelationships in these complementary seismological areas, we aim to build up a coherent picture of the latest advances and outstanding challenges in volcano seismology.
Hydraulic testing, frac operations and induced seismicity in geoenergy projects
Hydraulic stimulation is a well-operation that aims at enhancing fluid flow at depth. It is applied to exploit unconventional hydrocarbon reservoirs with low permeability and deep geothermal resources. Induced earthquakes frequently accompany the injection of fluids into boreholes potentially leading to damage to infrastructure at the surface and thus generally raising public concern. Damage caused by such events have already terminated Enhanced Geothermal Energy projects in South Korea and Switzerland. Hence, finding safe stimulation methods is critical for future use and public acceptance of geothermal energy projects and potential other forms of energy extraction from the underground. A range of stimulation techniques have been developed to increase the permeability of low-permeable reservoirs, however, our understanding of the processes involved in the formation of hydrofracs and hydroshears and the effectiveness of these operations regarding flow enhancement are still rather limited. A series of successful mine-back experiments have been performed in a range of underground laboratories in Europe. For this session, we invite presentations covering the full range of rock mechanics experiments, underground laboratory testing, and field-scale operations aiming at improving the fundamental understanding of stimulation operations.
Induced/triggered seismicity in geo-energy applications: monitoring, modeling, mitigation, and forecasting
Numerous cases of induced/triggered seismicity have been reported in the last decades as a result of the increasing interest in fluid injection/extraction projects related to geo-resources exploration. When such seismicity is felt by the population, it can 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, a key issue is to better understand how to monitor and model the processes leading to seismicity, in order to facilitate the development of effective and reliable forecasting methodologies during deep underground exploitation.
Given the complexity of induced seismicity processes and their interdisciplinary nature, understanding the triggering mechanisms implies to take into account coupled thermo-hydro-mechanical-chemical processes.
In this session, we invite contributions from research aimed at understanding such processes during exploitation of deep 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 modelling, spatio-temporal variations of physical parameters and seismicity, and fieldwork, covering both theoretical and experimental aspects of induced and triggered seismicity at multiple spatial and temporal scales.
Subduction zones are arguably the most important geological features of our planet, where plates plunge into the deep, metamorphic reactions take place, large earthquakes happen and melting induces volcanism and creation of continental crust. None of these processes would be possible without the cycling of volatiles, and this session aims to explore their role in convergent margins. Questions to address include the following. Do Atlantic and Pacific subduction zones cycle volatiles in different ways? What dynamic or chemical roles are played by subducted fracture zones and plate bending faults? How do fluids and melts interact with the mantle wedge and overlying lithosphere? Why do some of the Earth’s largest mineral resources form in subduction settings? We aim to bring together geodynamicists, geochemists, petrologists, seismologists, mineral and rock physicists, and structural geologists to understand how plate hydration/slab dynamics/dehydration, and subsequent mantle wedge melting/fluid percolation, and ultimately melt segregation/accumulation lead to the diverse range of phenomena observed at convergence zones around the globe.
Lena Melekhova (Bristol University)
Ingo Grevemeyer (GEOMAR)
We invite multidisciplinary contributions - both observational (seismology, geodetics, geobarometry etc.) and modelling (computational, analogue etc.) - on magma transport in the crust through dykes and sills. Understanding dykes and sills is vital as they serve both as the conduits that feed eruptions (and must be monitored to evaluate volcanic hazards), and as the bodies that build the crust. Although considerable uncertainties in our understanding of magma plumbing systems remain, recent events in Iceland (2014 Bárðarbunga-Holuhraun rifting event) have demonstrated how progress can be made by combining diverse observations from traditionally distinct disciplines.