What Governs the Spatial and Temporal Distribution of Aftershocks in Mining-Induced Seismicity: Insight into the Influence of Coseismic Static Stress Changes on Seismicity in Kiruna Mine, Sweden

2020 ◽  
Author(s):  
Maria Kozłowska ◽  
Beata Orlecka-Sikora ◽  
Savka Dineva ◽  
Łukasz Rudziński ◽  
Mirjana Boskovic
Keyword(s):  
Induced Seismicity ◽  
Temporal Distribution ◽  
Aftershock Sequence ◽  
State Model ◽  
Induced Earthquakes ◽  
Good Tool ◽  
Coulomb Stress Changes ◽  
Mining Induced Seismicity ◽  
Stress Changes ◽  
Natural Earthquakes

ABSTRACT Strong mining-induced earthquakes are often followed by aftershocks, similar to natural earthquakes. Although the magnitudes of such in-mine aftershocks are not high, they may pose a threat to mining infrastructure, production, and primarily, people working underground. The existing post-earthquake mining procedures usually do not consider any aspects of the physics of the mainshock. This work aims to estimate the rate and distribution of aftershocks following mining-induced seismic events by applying the rate-and-state model of fault friction, which is commonly used in natural earthquake studies. It was found that both the pre-mainshock level of seismicity and the coseismic stress change following the mainshock rupture have strong effects on the aftershock sequence. For mining-induced seismicity, however, we need to additionally account for the constantly changing stress state caused by the ongoing exploitation. Here, we attempt to model the aftershock sequence, its rate, and distribution of two M≈2 events in iron ore Kiruna mine, Sweden. We could appropriately estimate the aftershock sequence for one of the events because both the modeled rate and distribution of aftershocks matched the observed activity; however, the model underestimated the rate of aftershocks for the other event. The results of modeling showed that aftershocks following mining events occur in the areas of pre-mainshock activity influenced by the positive coulomb stress changes, according to the model’s assumptions. However, we also noted that some additional process not incorporated in the rate-and-state model may influence the aftershock sequence. Nevertheless, this type of modeling is a good tool for evaluating the risk areas in mines following a strong seismic event.

Short-Term Probabilistic Hazard Assessment in Regions of Induced Seismicity

2020 ◽  
Vol 110 (5) ◽  
pp. 2441-2453 ◽  
Author(s):  
Ganyu Teng ◽  
Jack W. Baker
Keyword(s):  
Hydraulic Fracturing ◽  
Induced Seismicity ◽  
Aftershock Sequence ◽  
Earthquake Occurrence ◽  
Induced Earthquakes ◽  
Short Term ◽  
Wastewater Disposal ◽  
West Texas ◽  
Hazard Level ◽  
Natural Earthquakes

ABSTRACT This project introduces short-term hazard assessment frameworks for regions with induced seismicity. The short-term hazard is the hazard induced during the injection for hydraulic-fracturing-induced earthquakes. For wastewater-disposal-induced earthquakes, it is the hazard within a few days after an observed earthquake. In West Texas, hydraulic-fracturing-induced earthquakes cluster around the injection activities, and the earthquake occurrence varies greatly in time and space. We develop a method to estimate the hazard level at the production site during the injection, based on past injection and earthquake records. The results suggest that the injection volume has a negligible effect on short-term earthquake occurrence in this case, because injection volumes per well fall within a relatively narrow range, whereas the regional variations in seismic productivity of wells and b-values are important. The framework could be easily modified for implementation in other regions with hydraulic-fracturing-induced earthquakes. We then compare the framework with wastewater-disposal-induced earthquakes in Oklahoma–Kansas and natural earthquakes in California. We found that drivers of short-term seismic hazard differ for the three cases. In West Texas, clustered earthquakes dominate seismic hazards near production sites. However, for Oklahoma–Kansas and California, the short-term earthquake occurrence after an observed mainshock could be well described by the mainshock–aftershock sequence. For Stillwater in Oklahoma, aftershocks contribute less to the hazard than San Francisco in California, due to the high Poissonian mainshock rate. For the rate of exceeding a modified Mercalli intensity of 3 within 7 days after an M 4 earthquake, the aftershock sequence from natural earthquakes contributed 85% of the hazard level, whereas the aftershock contribution was only 60% for induced earthquakes in Oklahoma. Although different models were implemented for hazard calculations in regions with hydraulic fracturing versus wastewater injection, injection activities could be drivers of short-term hazard in both cases.

scholarly journals Statistical physics models for aftershocks and induced seismicity

2018 ◽  
Vol 377 (2136) ◽  
pp. 20170397 ◽  
Author(s):  
Molly Luginbuhl ◽  
John B. Rundle ◽  
Donald L. Turcotte
Keyword(s):  
Induced Seismicity ◽  
Statistical Physics ◽  
Aftershock Sequence ◽  
Induced Earthquakes ◽  
Aftershock Activity ◽  
Gas Field ◽  
Natural Time ◽  
Parkfield Earthquake ◽  
Groningen Gas Field

A standard approach to quantifying the seismic hazard is the relative intensity (RI) method. It is assumed that the rate of seismicity is constant in time and the rate of occurrence of small earthquakes is extrapolated to large earthquakes using Gutenberg–Richter scaling. We introduce nowcasting to extend RI forecasting to time-dependent seismicity, for example, during an aftershock sequence. Nowcasting uses ‘natural time’; in seismicity natural time is the event count of small earthquakes. The event count for small earthquakes is extrapolated to larger earthquakes using Gutenberg–Richter scaling. We first review the concepts of natural time and nowcasting and then illustrate seismic nowcasting with three examples. We first consider the aftershock sequence of the 2004 Parkfield earthquake on the San Andreas fault in California. Some earthquakes have higher rates of aftershock activity than other earthquakes of the same magnitude. Our approach allows the determination of the rate in real time during the aftershock sequence. We also consider two examples of induced earthquakes. Large injections of waste water from petroleum extraction have generated high rates of induced seismicity in Oklahoma. The extraction of natural gas from the Groningen gas field in The Netherlands has also generated very damaging earthquakes. In order to reduce the seismic activity, rates of injection and withdrawal have been reduced in these two cases. We show how nowcasting can be used to assess the success of these efforts. This article is part of the theme issue ‘Statistical physics of fracture and earthquakes’.

Multi-phase hydromechanical modeling of induced seismicity: general insights and the case study of the deep geothermal project in St. Gallen, Switzerland

2020 ◽  
Author(s):  
Dominik Zbinden ◽  
Antonio Pio Rinaldi ◽  
Tobias Diehl ◽  
Stefan Wiemer
Keyword(s):  
Fluid Flow ◽  
Induced Seismicity ◽  
Gas Flow ◽  
Fluid Injection ◽  
Induced Earthquakes ◽  
Stress Changes ◽  
Reservoir Conditions ◽  
Multi Phase ◽  
Phase Fluid

<p>Industrial projects that involve fluid injection into the deep underground (e.g., geothermal energy, wastewater disposal) can induce seismicity, which may jeopardize the acceptance of such geo-energy projects and, in the case of larger induced earthquakes, damage infrastructure and pose a threat to the population. Such earthquakes can occur because fluid injection yields pressure and stress changes in the subsurface, which can reactivate pre-existing faults. Many studies have so far focused on injection into undisturbed reservoir conditions (i.e., hydrostatic pressure and single-phase flow), while only very few studies consider disturbed <em>in-situ</em> conditions including multi-phase fluid flow (i.e., gas and water). Gas flow has been suggested as a trigger mechanism of aftershocks in natural seismic sequences and can play an important role at volcanic sites. In addition, the deep geothermal project in St. Gallen, Switzerland, is a unique case study where an induced seismic sequence occurred almost simultaneously with a gas kick, suggesting that the gas may have affected the induced seismicity.</p><p>Here, we focus on the hydro-mechanical modeling of fluid injection into disturbed reservoir conditions considering multi-phase fluid flow. We couple the fluid flow simulator TOUGH2 with different geomechanical codes to study the effect of gas on induced seismicity in general and in the case of St. Gallen. The results show that overpressurized gas can affect the size and timing of induced earthquakes and that it may have contributed to enhance the induced seismicity in St. Gallen. Our findings can lead to a more detailed understanding of the influence of a gas phase on the induced seismicity.</p>

scholarly journals Pore-pressure diffusion, enhanced by poroelastic stresses, controls induced seismicity in Oklahoma

2019 ◽  
Vol 116 (33) ◽  
pp. 16228-16233 ◽  
Author(s):  
Guang Zhai ◽  
Manoochehr Shirzaei ◽  
Michael Manga ◽  
Xiaowei Chen
Keyword(s):  
Pore Pressure ◽  
Induced Seismicity ◽  
Energy Demand ◽  
Regional Scale ◽  
Exceedance Probability ◽  
Resource Exploitation ◽  
Induced Earthquakes ◽  
Seismicity Rate ◽  
Pressure Diffusion ◽  
Stress Changes

Induced seismicity linked to geothermal resource exploitation, hydraulic fracturing, and wastewater disposal is evolving into a global issue because of the increasing energy demand. Moderate to large induced earthquakes, causing widespread hazards, are often related to fluid injection into deep permeable formations that are hydraulically connected to the underlying crystalline basement. Using injection data combined with a physics-based linear poroelastic model and rate-and-state friction law, we compute the changes in crustal stress and seismicity rate in Oklahoma. This model can be used to assess earthquake potential on specific fault segments. The regional magnitude–time distribution of the observed magnitude (M) 3+ earthquakes during 2008–2017 is reproducible and is the same for the 2 optimal, conjugate fault orientations suggested for Oklahoma. At the regional scale, the timing of predicted seismicity rate, as opposed to its pattern and amplitude, is insensitive to hydrogeological and nucleation parameters in Oklahoma. Poroelastic stress changes alone have a small effect on the seismic hazard. However, their addition to pore-pressure changes can increase the seismicity rate by 6-fold and 2-fold for central and western Oklahoma, respectively. The injection-rate reduction in 2016 mitigates the exceedance probability of M5.0 by 22% in western Oklahoma, while that of central Oklahoma remains unchanged. A hypothetical injection shut-in in April 2017 causes the earthquake probability to approach its background level by ∼2025. We conclude that stress perturbation on prestressed faults due to pore-pressure diffusion, enhanced by poroelastic effects, is the primary driver of the induced earthquakes in Oklahoma.

scholarly journals SEISMICITY CHANGES DETECTION DURING THE SEISMIC SEQUENCES EVOLUTION AS EVIDENCE OF STRESS CHANGES

2017 ◽  
Vol 43 (4) ◽  
pp. 1994
Author(s):  
A.C. Astiopoulos ◽  
E. Papadimitriou ◽  
V. Karakostas ◽  
D. Gospodinov ◽  
G. Drakatos
Keyword(s):  
Temporal Distribution ◽  
Aftershock Sequence ◽  
Occurrence Rate ◽  
Generation Process ◽  
Seismicity Rate ◽  
Seismic Sequences ◽  
Epidemic Type Aftershock Sequence ◽  
Stress Changes ◽  
Lefkada Island ◽  
Seismicity Rate Changes

The statistical properties of the aftershock occurrence are among the main issues in investigating the earthquake generation process. Seismicity rate changes during a seismic sequence, which are detected by the application of statistical models, are proved to be precursors of strong events occurring during the seismic excitation. Application of these models provides a tool in assessing the imminent seismic hazard, oftentimes by the estimation of the expected occurrence rate and comparison of the predicted rate with the observed one. The aim of this study is to examine the temporal distribution and especially the occurrence rate variations of aftershocks for two seismic sequences that took place, the first one near Skyros island in 2001 and the second one near Lefkada island in 2003, in order to detect and determine rate changes in connection with the evolution of the seismic activity. Analysis is performed through space–time stochastic models which are developed, based upon both aftershocks clustering studies and specific assumptions. The models applied are the Modified Omori Formula (MOF), the Epidemic Type Aftershock Sequence (ETAS) and the Restricted Epidemic Type Aftershock Sequence (RETAS). The modelling of seismicity rate changes, during the evolution of the particular seismic sequences, is then attempted in association with and as evidence of static stress changes

The role of afterslip in driving aftershock sequences

2020 ◽  
Author(s):  
Robert Churchill ◽  
Maximilian Werner ◽  
Juliet Biggs ◽  
Ake Fagereng
Keyword(s):  
Empirical Relationship ◽  
Individual Case ◽  
Aftershock Sequence ◽  
Sequence Evolution ◽  
Coulomb Stress Changes ◽  
Temporal Decay ◽  
Aftershock Sequences ◽  
Stress Changes ◽  
Tectonic Earthquakes ◽  
Spatio Temporal

<p>Aftershock sequences following large tectonic earthquakes exhibit considerable spatio-temporal complexity and suggest causative mechanisms beyond co-seismic, elasto-static Coulomb stress changes in the crust. Candidate mechanisms include dynamic triggering and postseismic processes such as viscoelastic relaxation, poroelastic rebound and aseismic afterslip, which has garnered particular interest recently. Aseismic afterslip – whereby localized frictional sliding within velocity-strengthening rheologies acts to redistribute lithospheric stresses in the postseismic phase – has been suggested by numerous studies to exert dominant control on aftershock sequence evolution, including productivity, spatial distribution and temporal decay.</p><p>As evidence is based overwhelmingly on individual case study analysis, we wish to systematically compare key metrics of aseismic afterslip and corresponding aftershock sequences to investigate this relationship. We specifically look for any empirical relationship between the seismic-equivalent moment of aseismic afterslip episodes and the corresponding aftershock sequence productivity. We first compile published afterslip models into a database containing moment estimates over varying time periods, as well as spatial distributions, temporal decays and modelling methodology as a supplementary resource. We then identify the corresponding aftershock sequence from the globally comparable USGS PDE catalog. As expected, coseismic moment exerts an obvious control on both afterslip moment and aftershock productivity – an effect we control for by normalising by mainshock moment and expected productivity (the Utsu-Seki law) respectively. Preliminary results suggest broad variability of both afterslip moment and aftershock productivity with no obvious control of afterslip on aftershocks beyond the scaling with mainshock size, including when separated by mainshock mechanism or region. As this study is insensitive to spatial and temporal distributions, we cannot rule out the potential influence afterslip exerts in these but find no evidence that afterslip drives overall productivity of aftershock sequences.</p>

More Than 40 yr of Potentially Induced Seismicity Close to the San Andreas Fault in San Ardo, Central California

2020 ◽  
Vol 92 (1) ◽  
pp. 187-198
Author(s):  
Thomas H. W. Goebel ◽  
Manoochehr Shirzaei
Keyword(s):  
Induced Seismicity ◽  
Surface Deformation ◽  
Active Faults ◽  
Stress Transfer ◽  
Correlation Coefficients ◽  
Spatial Proximity ◽  
Fluid Injection ◽  
Induced Earthquakes ◽  
Temporal Correlations ◽  
Stress Changes

Abstract Evidence for fluid-injection-induced seismicity is rare in California hydrocarbon basins, despite widespread injection close to seismically active faults. We investigate a potential case of injection-induced earthquakes associated with San Ardo oilfield operations that began in the early 1950s. The largest potentially induced events occurred in 1955 (ML 5.2) and 1985 (Mw 4.5) within ∼6  km from the oilfield. We analyze Synthetic Aperture Radar interferometric images acquired by Sentinel-1A/B satellites between 2016 and 2020 and find surface deformation of up to 1.5  cm/yr, indicating pressure-imbalance in parts of the oilfield. Fluid injection in San Ardo is concentrated within highly permeable rocks directly above the granitic basement at a depth of ∼800  m. Seismicity predominantly occurs along basement faults at 6–13 km depths. Seismicity and wastewater disposal wells are spatially correlated to the north of the oilfield. Temporal correlations are observed over more than 40 yr with correlation coefficients of up to 0.71 for seismicity within a 24 km distance from the oilfield. Such large distances have not previously been observed in California but are similar to the large spatial footprint of injection in Oklahoma. The San Ardo seismicity shows anomalous clustering with earthquakes consistently occurring at close spatial proximity but long interevent times. Similar clustering has previously been reported in California geothermal fields and may be indicative of seismicity driven by long-term, spatially persistent external forcing. The complexity of seismic behavior at San Ardo suggests that multiple processes, such as elastic stress transfer and aseismic slip transients, contribute to the potentially induced earthquakes. The present observations show that fluid-injection operations occur close to seismically active faults in California. Yet, seismicity is predominantly observed on smaller unmapped faults with little observational evidence that large faults are sensitive to induced stress changes.

scholarly journals Induced seismicity in geologic carbon storage

2019 ◽  
Author(s):  
Víctor Vilarrasa ◽  
Jesus Carrera ◽  
Sebastià Olivella ◽  
Jonny Rutqvist ◽  
Lyesse Laloui
Keyword(s):  
Carbon Storage ◽  
Induced Seismicity ◽  
Public Perception ◽  
Fault Reactivation ◽  
Wellbore Stability ◽  
Rock Properties ◽  
Induced Earthquakes ◽  
Geologic Carbon Storage ◽  
Stress Changes ◽  
Injection Formation

Abstract. Geologic carbon storage, as well as other geo-energy applications, such as geothermal energy, seasonal natural gas storage and subsurface energy storage, imply fluid injection/extraction that causes changes in the effective stress field and induces (micro)seismicity. If felt, seismicity has a negative effect on public perception and may jeopardize wellbore stability and damage infrastructure. Thus, induced earthquakes should be minimized to successfully deploy geo-energies. However, the processes that trigger induced seismicity are not fully understood, which translates into a limited forecast ability of current predictive models. We aim at understanding the triggering mechanisms of induced seismicity and to develop methodologies to minimize its occurrence through dimensional and numerical analysis. We find that the properties of the injected fluid, e.g., water or CO2, have a significant effect on pressure buildup evolution and thus, on fracture/fault stability. In addition to pressure changes, the injected fluid usually reaches the injection formation at a lower temperature than that of the rock, inducing rock contraction, thermal stress reduction and stress redistribution around the cooled region. If low-permeable faults cross the injection formation, local stress changes are induced around them which may reduce their stability and eventually cause fault reactivation. To minimize the risk of inducing felt seismicity, we have developed characterization techniques to reduce the uncertainty on rock properties and subsurface heterogeneity both for the screening of injection sites and for the operation of projects. Overall, we contend that felt induced seismicity can be minimized provided that a proper site characterization, monitoring and pressure management are performed.

scholarly journals Coulomb static stress changes before and after the 23 October 2011 Van, eastern Turkey, earthquake (<i>M</i><sub>W</sub>= 7.1): implications for the earthquake hazard mitigation

2013 ◽  
Vol 13 (7) ◽  
pp. 1889-1902 ◽  
Author(s):  
M. Utkucu ◽  
H. Durmuş ◽  
H. Yalçın ◽  
E. Budakoğlu ◽  
E. Işık
Keyword(s):  
Earthquake Hazard ◽  
Aftershock Sequence ◽  
Coulomb Stress ◽  
Van Earthquake ◽  
Coulomb Stress Changes ◽  
Stress Shadow ◽  
Eastern Turkey ◽  
Stress Changes ◽  
Before And After ◽  
2011 Van Earthquake

Abstract. Coulomb stress changes before and after the 23 October 2011 Van, eastern Turkey, earthquake have been analysed using available data related to the background and the aftershock seismicity and the source faults. The coseismic stress changes of the background seismicity had slightly promoted stress over the rupture plane of the 2011 Van earthquake, while it yielded a stress shadow over the Gürpı nar Fault which has been argued to have produced the 7 April 1646 Van earthquake. The stress shadow over the Gürp\\i nar fault has become more pronounced following the occurrence of the 2011 Van earthquake, meaning that the repetition of the 1646 Van earthquake has been further suppressed. Spatial distribution and source mechanisms of the 2011 Van earthquake's aftershocks have been utilised to define four clusters with regard to their relative location to the mainshock rupture. In addition, the aftershock sequence covers a much broader area toward the northeast. Correlations between the observed spatial patterns of the aftershocks and the coseismic Coulomb stress changes caused by the mainshock are determined by calculating the stress changes over both optimally oriented and specified fault planes. It is shown here that there is an apparent correlation between the mainshock stress changes and the observed spatial pattern of the aftershock occurrence, demonstrating the usefulness of the stress maps in constraining the likely locations of the upcoming aftershocks and mitigating earthquake hazard.

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