Recent Induced Seismicity Papers IV

Here is the fourth part of our presentation of recent papers related to induced seismicity. If you want to advertise your paper or have any suggestions, do not hesitate to contact us.

Schoenball, M., L. Dorbath, E. Gaucher, J. F. Wellmann, and T. Kohl (2014). Change of stress regime during geothermal reservoir stimulation. Geophysical Research Letters 41, 1163–1170, doi 10.1002/2013GL058514.

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Earthquakes are induced by man-made changes of the stress field by injection or withdrawal of fluids in hydrocarbon production, geothermal exploitation, and wastewater disposal. However, the actual perturbation of the stress field and stress release by injection-induced seismicity remains largely unknown. We provide evidence for currently not understood hydromechanical processes after shut-in of the well. We invert earthquake focal mechanisms from a massive stimulation to invert for stress resolved in time and depth to obtain changes of the stress orientation and magnitude. Prior information about fracture orientations from well logs is taken into account. Comparison with independent stress measures reveals that stresses obtained from inversion of fluid-induced seismicity are highly perturbed and not representative of the initial stress field. The horizontal stresses change by tens of megapascals, turning the stress regime from transitional normal faulting/strike-slip faulting to pure normal faulting. The observed stress changes are attributed to large-scale aseismic deformation.

Link: Article website

Cartlidge, E. (2014). Human Activity May Have Triggered Fatal Italian Earthquakes, Panel Says. Science 344, 141.

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In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly earthquakes that struck the Italian region of Emilia-Romagna in 2012 could have been triggered by the extraction of petroleum at a local oil field. Fear of humanmade seismicity has already sparked fierce opposition against new oil and gas drilling efforts in Italy, and some say the report could lead the country’s regional presidents to turn down new requests for fossil-fuel exploration.

Link: Article website

Guilhem, A., L. Hutchings, D. S. Dreger, and L. R. Johnson (2014), Moment tensor inversions of M~ 3 earthquakes in the Geysers geothermal fields, California, J. Geophys. Res. Solid Earth, 119, doi:10.1002/2013JB010271.

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Microearthquakes have come into high public awareness due to being induced by the development and exploitation of enhanced and natural geothermal fields, hydrofracturing, and CO2 sequestration sites. Characterizing and understanding the faulting process of induced earthquakes, which is generally achieved through moment tensor inversion, could both help in risk prediction and in reservoir development monitoring. However, this is a challenging task because of their lower signal-to-noise ratio at frequencies typically used in earthquake source analyses. Therefore, higher-resolution velocity models and modeling of seismic waves at higher frequencies are required. In this study, we examine both the potentials to obtain moment tensor solutions for small earthquakes and the uncertainty of those solutions. We utilize a short-period seismic network located in the Geysers geothermal field in northern California and limit our study to that which would be achieved by industry in a typical reservoir environment. We obtain full moment tensor solutions of M ~ 3 earthquakes using waveform modeling and first-motion inversions. We find that these two data sets give complimentary but yet different solutions. Some earthquakes correspond possibly to complex processes in which both shear and tensile failures occur simultaneously or sequentially. This illuminates the presence of fluids at depth and their role for the generation of these small-magnitude earthquakes. Finally, since first motions are routinely obtained for all magnitude earthquakes, our approach could be extended to small earthquakes where noise level and complex Green’s functions prohibit using waveforms in moment tensor inversions.

Link: Article website

Zhao, P., D. Kühn, V. Oye, and S. Cesca Evidence for tensile faulting deduced from full waveform moment tensor inversion during the stimulation of the Basel enhanced geothermal system. Geothermics doi 10.1016/j.geothermics.2014.01.003

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Our study presents the results of a moment tensor inversion of 19 microseismic events with ML between 2.0 and 3.4, associated with the stimulation operation of an enhanced geothermal reservoir in Basel, Switzerland, in 2006. We adopt a three-step procedure to retrieve point source solution parameters based on full waveform inversion. The inversion is performed by fitting displacement amplitude spectra and displacement seismograms in the first and second step, respectively, assuming a double couple source model and thus obtaining focal solutions for all 19 events. Our results are in agreement with focal mechanisms from a previous study, which employed P wave first-motion polarities from more than 40 stations, whereas our solutions are achieved using full waveform data recorded by less than 10 surface stations. In the last step, a full moment tensor inversion is performed. The results from the moment tensor inversion show an improvement on the waveform fitting compared to the double couple models, which is verified by an F-test. We investigate the stability of the moment tensor solutions by employing different velocity models. The isotropic components of the moment tensor solutions of some events are not negligible, suggesting source volume changes due to fluid injection. Events with significant isotropic components occurred mainly during the stimulation phase and close to the injection well. On the other hand, events that occurred in the post-stimulation phase are predominantly pure shear failure and located further away from the well bore. These spatio-temporal patterns can be explained by the influence of pore pressure variations during and after the hydraulic stimulation at the geothermal site.

Link: Article website

Orlecka-Sikora, B., S. Cesca, S. Lasocki, G. Lizurek, P. Wiejacz, and Ł. Rudziński (2014). Seismogenesis of exceptional ground motion due to a sequence of mining induced tremors from Legnica-Głogów Copper District in Poland. Geophysical Journal International. doi

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A series of six seismic events that occurred in one panel of Rudna copper-ore mine in Poland is studied. Although the events had comparable magnitudes, from 3.0 to 3.7, their ground effects were very diverse. Comparing the accelerations observed at various locations with their estimates from ground motion prediction equation the events split into three distinct pairs. The first pair ground effects exceed considerably the estimates at most of observation points, the second pair effects are abnormally high at short epicentral distances, whereas the third pair effects are much less than the estimates at most of observation points. The similarities in ground effects correlate with the fault mechanisms similarities. The first two pairs’ events, whose ground effects were strong, exhibit thrust faulting and the third pair events, which caused unexpectedly low ground motion exhibit normal faulting mechanisms. The paired events have also similar apparent stress values. These stress values of the two events of very weak ground effects are distinctly lower than the values of other four events. All events demonstrate dominating non-double-couple components in the overall mechanisms. A kinematic source analysis indicates that these events have extended rather than point sources, and five of them have distinct directivity effects. A static stress transfer analysis signifies interrelations between these events. The rupture of all events started in areas of Coulomb failure function increase due to the cumulative effect of previous events. Linking results of the ground effects, source, rupture and interaction analyses tentative geodynamic conclusions are formulated. The untypical and diverse ground effects of the studied events result likely from the events’ complexity expressed by tensile source mechanisms, finite sources, directivity of ruptures and nearly horizontal rupture planes. The above features seem to be implied by a superposition of coseismic alterations of stress field and stress changes due to mining. One cannot, therefore, exclude the possibility of other cases of significant deviations from the expected ground motion amplitudes, due to specific geodynamics in another parts of the mine. An analysis like that done within this work can allow, however, foreseeing such extreme surface impacts.

Link: Article website

IASPEI Regional Assembly – Reminder

Dear Colleagues,

Let us remind you that within a few days from today we shall reach the deadline for submitting abstracts (May 23rd) to IASPEI – REGIONAL ASSEMBLY, Latin American and Caribbean Seismological Commission – LACSC: BOGOTA, COLOMBIA: JULY 23 – 25, 2014.

To submit an abstract please visit the web page: http://geoslac.org/english

Best regards and wishes
Stan Lasocki, Adi do Nascimento, Carlos Vargas
Conveners, ANST – LACSC IASPEI 2014

SESSION DESCRIPTION

The phenomenon of anthropogenic seismic activity is an unwanted rockmass response to human technological processes. With rising demands for energy and minerals this type seismicity appears in areas previously known as aseismic and  in association with quite diverse technological processes. The induced earthquakes accompany underground and open-pit mining, conventional and unconventional hydrocarbon production, reservoir impoundment, geothermal energy production, underground fluid and gas storage including carbon sequestration and many other technological processes that perturb the boundary conditions in the affected rockmass. The socio-economic impact of the induced seismicity is very significant. On the one hand, these events, though being small compared to tectonic earthquakes, because of their shallowness are often damaging and occasionally devastating. On the other hand, the hazards associated with triggered earthquakes can be and are often overrated. It is clear that vital technological activities can lose public confidence unless the accompanying seismic risks are accurately assessed and properly presented to public. Finally, earthquakes whose origin, whether natural or anthropogenic, is under debate, pose questions that need to be answered with high certainty.

The goal of this session is to recognize the severity of the induced and triggered seismicity world-widely, and to summarize the present state of knowledge about these seismic processes. We welcome both cross-sectional multi-aspect theoretical, methodical and experimental studies as well as interesting case histories linked to particular inducing technologies. The session is meant, among others, to help in identifying common areas of seismic processes induced by different technologies. Consideration on the predictability and controllability of anthropogenic earthquakes are especially invited.

IASPEI Regional Assembly, Session on Antropogenic Seismicity

Please find enclosed the information on the IASPEI – REGIONAL ASSEMBLY of the Latin American and Caribbean Seismological Commission – LACSC, BOGOTA, COLOMBIA: JULY 23 – 25, 2014. The session ANST – ANTHROPOGENIC SEISMICITY is conveyed by Stanislaw Lasocki (Institute of Geophysics Polish Academy of Sciences, Warsaw, Poland),  Aderson Farias do Nascimento (Departamento de Fisica – UFRN – Natal RN, Brasil) and Carlos Alberto Vargas Jimenez (Departamento de de Geociencias – Universidad Nacional de Colombia).

Abstract

The phenomenon of anthropogenic seismic activity is an unwanted rockmass response to human technological processes. With rising demands for energy and minerals this type seismicity appears in areas previously known as aseismic and in association with quite diverse technological processes. The induced earthquakes accompany underground and open-pit mining, conventional and unconventional hydrocarbon production, reservoir impoundment, geothermal energy production, underground fluid and gas storage including carbon sequestration and many other technological processes that perturb the boundary conditions in the affected rockmass. The socio-economic impact of the induced seismicity is very significant. On the one hand, these events, though being small compared to tectonic earthquakes, because of their shallowness are often damaging and occasionally devastating. On the other hand, the hazards associated with triggered earthquakes can be and are often overrated. It is clear that vital technological activities can lose public confidence unless the accompanying seismic risks are accurately assessed and properly presented to public. Finally, earthquakes whose origin, whether natural or anthropogenic, is under debate, pose questions that need to be answered with high certainty.

The goal of this session is to recognize the severity of the induced and triggered seismicity world-widely, and to summarize the present state of knowledge about these seismic processes. We welcome both cross-sectional multi-aspect theoretical, methodical and experimental studies as well as interesting case histories linked to particular inducing technologies. The session is meant, among others, to help in identifying common areas of seismic processes induced by different technologies. Consideration on the predictability and controllability of anthropogenic earthquakes are especially invited.

The deadline for submission of abstracts is May 23, 2014.

For details and to submit an abstract please contact the web page: http://geoslac.org/english/

 

Sessions at EGU

As the deadline for submitting an abstract for EGU 2014 general assembly in Vienna is approaching (16 January!), I would like to draw your attention on three sessions that are induced-seismicity related:

Induced and Triggered Seismicity: Theory and Observations (co-organized)

Convener: Philippe Jousset | Co-Conveners: Roland Gritto , Matteo Lupi

Link: Abstract submission

Earthquake source processes – Imaging methods, physical rupture models and scaling (co-organized)

Convener: P. Martin Mai | Co-Conveners: Grzegorz Kwiatek, Rebecca M. Harrington, Henriette Sudhaus, Alice Gabriel

Link: Abstract submission

Induced seismicity and geomechanics in mining and reservoir production: Laboratory and field perspective.

Convener: Grzegorz Kwiatek | Co-Conveners: Hiroki Sone, Beata Orlecka-Sikora, Katrin Plenkers, Philip Benson, D. Kuehn

Link: Abstract submission

Session on Induced Seismicity at SSA2014

On behalf of Conveners, I would like to draw your attention to the Induced Seismicity session organized by Ivan Wong, Justin Rubinstein and Thomas Braun during SSA2014 meeting in Anchorage, Alaska. The meeting will take place between 30 April – 2 May, 2014, and the abstract submission deadline is January 10th, 2014. Below we attach the abstract of the Induced Seismicity session; the detailed information on the conference can be found here together with SSA2014 programme webpage.

Abstract

Recent damaging earthquakes in Oklahoma, Colorado, and Arkansas have renewed interest in induced seismicity. Across the central and eastern United States, the seismicity rate has doubled over the past 11 years. This rate change can largely be attributed to earthquakes induced by fluid injection associated with oil and gas production. Given the occurrence of damaging earthquakes and the large increase in seismicity rate observed in the United States, it is of critical importance that induced earthquakes are better understood such that their hazards may be mitigated. Topics of interest to address these issues include: the causes of fluid-injection induced earthquakes; methods to distinguish natural and induced earthquakes; why some wells trigger earthquakes, but the vast majority of wells do not; how fluid-injection induced earthquakes may be controlled; and how to estimate the hazard associated with already developed and new fluid injection fields. We invite papers on all forms of induced seismicity but particularly those associated with waste water-injection, geothermal production, carbon sequestration, and hydraulic fracturing. Papers from industry are particularly welcome to better inform the research community on the state of knowledge and practices within the community. As part of this session, a roundtable discussion will be held to discuss (1) the factors influencing induced seismicity, (2) the uncertainties in characterizing induced seismicity, (3) strategies to control induced seismicity, and (4) methods to characterize the earthquake hazards associated with fluid injection.

Thanks to Thomas Braun for information regarding the session.