Microseismicity, Induced Seismicity, Earthquake Mechanism

FOR CITATION: Salem, Hilmi S. (2020). Multi-and Inter-Disciplinary Approaches Towards Understanding the Sinkholes' Phenomenon in the Dead Sea Basin, SN Applied Sciences, (2020) 2:667. https://doi.org/10.1007/s42452-020-2146-0. Springer URL: https://www.researchgate.net/publication/339044303_Multi-and_Inter-Disciplinary_Approaches_Towards_Understanding_the_Sinkholes'_Phenomenon_in_the_Dead_Sea_Basin_SN_Applied_Sciences_Springer_March_2020/stats

ABSTRACT: Over the last few decades, thousands of sinkholes have developed at an increasing pace, with the majority along the western and eastern shores of the Dead Sea. Recent studies indicate that the number of sinkholes in the Dead Sea Basin (DSB) has reached more than 6000; each of them, on average, 1–10 m deep and up to 25–30 m in diameter. These sinkholes can open-up suddenly and swallow whatever exists above them, resulting in an area that looks like an earthquake zone. Sinkholes in the DSB are formed when a subterranean salt layer that once bordered the Dead Sea is dissolved by underground freshwater that follows the migration of the saltwater–freshwater interface, due to receding water level of the Dead Sea. Consequently, large areas of land are subsiding, causing the formation of sinkholes in the region. Also, based on the fact that the Dead Sea’s region is tectonically and seismically active, as being greatly affected by the Dead Sea transform fault system, sinkholes can also be evolved as a result of tectonic and seismic activities. This paper presents multi- and inter-disciplinary approaches towards understanding the occurrence of sinkholes in the DSB, with respect to geomorphology, geology, geophysics, tectonics, seismology, limnology, climatology, biodiversity, and socioeconomics, as well as the steady decline of the Dead Sea’s water level and the continuous shrinkage of its surface area and its water volume, at alarming rates. The occurrence of sinkholes in this region could be attributed to anthropogenic reasons and/or natural reasons.
KEYWORDS: Sinkholes · Dead Sea Basin · Water level’s decline · Surface area’s shrinkage · Anthropogenic causes · Naturally induced · Brine and freshwater · Tectonics and seismicity · Transform fault system

Light Crude Oil (LCO) is currently used for power generation at the 330 MW combined cycle plant at Takoradi Thermal Station. However, the plant is to be modified to operate on Natural Gas (NG). This paper deals with the validation of a thermodynamic model that was used to evaluate the performance of this plant using both LCO and NG. The model inputs and outputs included the ambient air temperature and pressure, compressor pressure ratio, component efficiencies, air flow rate in compressor, mass of fuel, fuel calorific values, compressor power input, pressure of water in the heat recovery steam generator (HRSG), temperature of flue gas at the exit of the HRSG, temperature of water at pump inlet, mass flows of steam and cooling water and the net power from both the gas and steam turbines. Mass and energy balance equations were used for the model development. It is concluded that less mass of NG is required to produce the same power output as compared to LCO at the same operating conditions. Thus, it is economically feasible and beneficial to TTPS to change from LCO to NG for its operations.

Measurements of the strains and earthquakes induced by fluid extraction from a subsurface reservoir reveal a transient, exponential-like increase in seismicity relative to the volume of fluids extracted. If the frictional strength of these reactivating faults is heterogeneously and randomly distributed, then progressive failures of the weakest fault patches account in a general manner for this initial exponential-like trend. Allowing for the observable elastic and geometric heterogeneity of the reservoir, the spatiotemporal evolution of induced seismicity over 5 years is predictable without significant bias using a statistical physics model of poroelastic reservoir deformations inducing extreme threshold frictional failures of previously inactive faults. This model is used to forecast the temporal and spatial probability density of earthquakes within the Groningen natural gas reservoir, conditional on future gas production plans. Probabilistic seismic hazard and risk assessments based on these forecasts inform the current gas production policy and building strengthening plans. Plain Language Summary On rare occasions industrial activities create earthquakes that are sufficiently big and frequent to cause concern about the possibility of building damage and injury. One such example is Western Europe's largest producing natural gas field located next to the city of Groningen in the northeast of the Netherlands. If the physical processes that induce these earthquakes can be understood, then it might be possible to reduce the risks to acceptable levels by reducing the amount of natural gas extracted from below ground each year or by selectively strengthening buildings. A new theory was created to describe how extracting fluids, such as natural gas, from under the ground may distort the surrounding rocks in such a way that they occasionally and abruptly slide past each other forming an earthquake. Using this theory, the timing, location, and number of previous earthquakes within the Groningen gas field may be properly explained and the chance of further earthquakes in the coming few years can be reliably forecasted. These earthquake forecasts are now used to inform choices about how to safely extract the remaining gas from the Groningen field which is capable of supplying the European gas market for at least another 40 years.

In this work, we modeled double- and triple-cluster 3D hydraulic fracturing in a single-layer, quasi-brittle shale formation using planar CZM and XFEM-based CZM including slit flow and poro-elasticity for fracture and matrix spaces, respectively, in Abaqus. Our fully-coupled pore pressure-stress Geo-mechanics model includes leak-off as a continuum-based fluid flow component coupled with the other unknowns in the problem. Having compared the triple-cluster fracturing results from planar CZM with those from XFEM-based CZM, we found that the stress shadowing effect of multiple hydraulic fractures on each other can cause these fractures to rationally propagate out of plane; this also demonstrates the advantages of the second method compared to the first one. We investigated the effect of this arbitrary propagation direction on not only the fractures’ length, aperture, and the required injection pressure, but also fractures’ connection to the wellbore. Depending on the spacing and the number of clusters per stage, this connection can be gradually disrupted with time due to the near-wellbore fracture closure which may embed proppant particles on the fracture wall, or screen out the fracture at early stimulation times. Comparing all studied cases, we concluded that the double-cluster, simultaneous fracturing with 100-ft spacing provides the most viable fracture set for long-term production.

A Monte Carlo approach to probabilistic seismic-hazard analysis is developed for a case of induced seismicity associated with a compacting gas reservoir. The geomechanical foundation for the method is the work of Kostrov (1974) and McGarr (1976) linking total strain to summed seismic moment in an earthquake catalog. Our Monte Carlo method simulates future seismic hazard consistent with historical seismic and compaction datasets by sampling probability distributions for total seismic moment, event locations and magnitudes, and resulting ground motions. Ground motions are aggregated over an ensemble of simulated catalogs to give a prob-abilistic representation of the ground-motion hazard. This approach is particularly well suited to the specific nature of the time-dependent induced seismicity considered. We demonstrate the method by applying it to seismicity induced by reservoir com-paction following gas production from the Groningen gas field. A new ground-motion prediction equation (GMPE) tailored to the Groningen field, has been derived by calibrating an existing GMPE with local strong-motion data. For 2013–2023, we find a 2% chance of exceeding a peak ground acceleration of 0:57g and a 2% chance of exceeding a peak ground velocity of 22 cm=s above the area of maximum compaction. Disaggregation shows that earthquakes of M w 4–5, at the shortest hypocentral distances of 3 km, and ground motions two standard deviations above the median make the largest contributions to this hazard. Uncertainty in the hazard is primarily due to uncertainty about the future fraction of induced strains that will be seismogenic and how ground motion and its variability will scale to larger magnitudes.

Penelitian mengenai Area Geothermal Kamojang telah banyak dilakukan, namun dari sekian penelitian
tersebut hanya berfokus pada metode gravity. Pada penelitian ini metode yang digunakan untuk monitoring
Area Geothermal Kamojang adalah metode MEQ (Micro-Earthquake) dengan tujuan memperoleh sebaran
hiposenter menggunakan metode penentuan hiposenter SED (Single Event Determination). Gempa mikro
pada suatu area geothermal disebabkan oleh adanya zona lemah yang terbuka akibat injeksi air, zona
tersebut akan semakin terbuka seiring pertambahan volume, laju, dan tekanan air reinjeksi, adanya kontak
antara air dingin dengan batuan reservoir yang panas maupun heat-source, serta berkurangnya pori batuan
akibat hilangnya fluida pengisi peori tersebut sebagai dampak aktivitas produksi. Karakteristik gempa mikro
yaitu memiliki magnitudo 􀂔 3 SR (Skala Richter) serta durasi gempanya yang tidak akan lebih dari satu menit.
Metode penentuan hiposenter gempa yang dikembangkan oleh Geiger (1910) yaitu metode SED merupakan
sebuah proses iterasi dengan optimasi Gauss-Newton untuk menentukan lokasi sumber gempa bumi.
Metode tersebut merupakan pemodelan ke depan dengan tujuan meminimalkan nilai travel time residual
antara arrival time yang teramati dengan arrival time yang diprediksi atau hasil pemodelan. Dari pengolahan
data rekaman gempa selama bulan April – Mei 2014, diperoleh 56 events/kejadian gempa mikro dengan
rincian terdapat 39 events yang memiliki magnitudo gempa 0,1 SR, 14 events dengan magnitudo 0,2 SR, 2
events 0,3 SR, serta 1 events magnitudo 0,4 SR. Mayoritas hiposenter gempa yang diperoleh dari
pengolahan data ternyata berada di luar Area Geothermal Kamojang.

Efforts to diversify the energy portfolio and to alleviate environmental impacts are rendering the activity of injecting fluid into a geologic formation as important as extracting fluid from it. Fluid injection that is associated with a thermal effect can cause more complex geomechanical responses than fluid extraction does. To test these responses, we conducted in-depth investigations of pore-pressure buildup, temperature, and stress changes under isothermal or nonisothermal injection scenarios, using numerical simulations. The numerical simulation method combines fluid flow, poroelasticity, thermal diffusion, and thermal stress, and is based on the single-phase fluid flow condition. We also examined temporal evolutions of stress states and mobilized friction angles across base, injection zone, and caprock layers for two different stress regimes, normal-faulting and reverse-faulting. Results show that injecting cold fluid shifts an area in which the mobilized friction angle becomes maximum, which is where induced-seismic events are likely to be triggered first, for both stress regimes. We also tested a hypothetical stepwise injection of cold fluid; results show that this injection helps to improve the stability of the injection zone to some extent. Finally, we suggest using dimensionless parameters to determine a prevalence of the thermal-stress effect in the injection zone, and discuss the impact of the initial stress regime and implications of using the single-phase fluid flow condition.

Aswan High Dam ( AHD) located at the north of Nasser's Lake in Aswan , Egypt, has a vital role as it is a multipurpose mega project for sustainable irrigation development, hydropower, navigation improvement  etc… In this work we aim to detect the hazardous subsurface structures controlling the south west of Aswan area and the causative source depths through the application of both normalized standard deviations (NSTD) filter and deconvolution procedure utilizing 3-D Euler homogeneity equation with un-prescribed structural indices based on the properties of the differential similarity transformation (DST) on the available Bouguer gravity data. Hence without any bias to definite structural elements (SI), an automatic identification of the effective structural indices in the area is given. Moreover, possible vertical magnetic contacts are estimated from the reduced to pole magnetic anomaly map through the application of tilt depth technique. The integration of potential field data analysis with the analysis of the new seismological catalogue data together with water level data shows that the area began a hazardous cycle of activity which may last for about ten years. The b-value changes and the rate of shallow high magnitude events increased dramatically. More attention has to be paid for such important area.

The occurrence time of earthquakes can be anticipated or delayed by external phenomena that induce strain energy changes on the faults. ‘Anticipated’ earthquakes are generally called ‘triggered’, however it can be controversial to label a specific earthquake as such, mostly because of the stochastic nature of earthquake occurrence and of the large uncertainties usually as- sociated to stress modelling. Here we introduce a physical approach to quantify the probability that a given earthquake was triggered by a given stress-inducing phenomenon. As an example, we consider an earthquake that was likely triggered by a natural event: the M=6.2 13 Jan 1976 Ko ́pasker earthquake on the Gr ́ımsey Lineament (Tj ̈ornes Fracture Zone, Iceland), which occurred about three weeks after a large dike injection in the nearby Krafla fissure swarm. By using Coulomb stress calculations and the rate-and-state earthquake nucleation theory, we calculate the likelihood of the earthquake in a scenario that contains only the tectonic background and excludes the dike, and in a scenario that includes the dike but excludes the background. Applying the Bayes’ theorem, we obtain that the probability that the earthquake was indeed triggered by the dike, rather than purely due to the accumulation of tectonic strain, is about 60% to 90%. This methodology allows us to assign quantitative probabilities to different scenarios and can help in classifying earthquakes as triggered or not-triggered by natural or human-induced changes of stress in the crust.combined statistical and

We study the surface deformation of a moderate size M5+ earthquake swarm-type activity which burst at the tip of the Biga peninsula (western Turkey) in early 2017. No previous M5+earthquakes have been recorded in the instrumental period on land, however, offshore normal faults, have ruptured to produce strong (M > 6) earthquakes. We use the Interferometric Synthetic Aperture Radar (InSAR) technique and exploit a data set of Sentinel-1 and ALOS-2 images, to successfully detect the surface deformation caused by three M5+ events of the sequence and constrain their source models, furtherly strengthened by seismic waveform analysis. The sequence occurred at shallow depths (<12 km) and is related with the activation of a normal fault. Our geodetic inversions constrained the rupture distribution of the main events and led us to conclude that they belong to a single fault plane, striking N110 • E and dipping ∼40 • to the SW, compatible with the regional tectonics. Furthermore, the InSAR analysis revealed that no aseismic transients occurred during the Biga swarm. InSAR applications in seismic swarms are limited mainly due to the low displacement signal they produce, which is not always easily detectable by radar satellites. Another obstacle is the time frequency of radar satellites acquisitions that often does not allow the temporal isolation of distinct seismic events. However, here we present a study that exploits InSAR data to isolate seismic sources of a swarm and proposes its use for the understanding of shallow seismic swarms in a systematic manner.

Coastal upwelling along the coast of California has become more variable than during nearly any period in the past 600 years. Black et al. used a 576-year tree ring record to construct a record of wintertime climate along the California coast. Because wintertime climate and coastal upwelling are so closely linked there, they were able to determine that upwelling variability has increased more over the past 60 years than for all but two intervals during that time. The apparent causes of the recent trend appear to be unique, resulting in reduced marine productivity and negative impacts on fish, seabirds, and mammals.

Seismic moment tensors provide a general mathematical representation of point sources that can be used to distinguish between various microseismic source types. We use synthetic tests with borehole receiver arrays to determine the geometrical conditions necessary to estimate reliably the six independent components of a full moment tensor by leastsquares inversion. We show that the solid angle subtended by the receiver array, as viewed from the source location, plays a fundamental role in the stability of the inversion. In particular, the condition number of the generalized inverse scales linearly with the solid angle, implying that for a solid angle of zero (as is the case for a single vertical borehole) the inversion is ill-conditioned. Our numerical tests indicate that least squares moment-tensor solutions obtained under such nonideal conditions tend to be biased toward double-couple (i.e., mode II or II fracture) mechanisms. Our findings suggest that caution should be exercised in the interpretation of momenttensor solutions from microseismic field experiments. Possible strategies to alleviate this concern could be to ensure a nonzero solid-angle aperture by using multiple observation wells, or to incorporate other types of data such as a priori knowledge of fracture orientation to constrain the solutions.

Una secuencia sísmica, que culminó en terremotos de magnitud hasta 4.3, se originó en septiembre y octubre de 2013 frente a las costas de Castellón (España), cerca de donde se estaba inyectando subterráneamente gas natural para almacenarlo en un yacimiento petrolífero agotado (el llamado Proyecto Castor). Este artículo analiza esta serie de terremotos desde el punto de vista tectónico y sismológico, y su relación con la inyección de gas.

Earthquakes can be induced by reservoir impoundment, fluid injection, mining, or oil and gas extraction. These induced quakes create a risk of personal injury or damage to property. The quakes induced at the Rocky Mountain Arsenal near Denver in the 1960's caused significant property damage. Currently, low level seismicity is being induced at several sites in Colorado, including the Rangely Oilfield, Paradox Valley, and Ridgway Reservoir areas. However, no Colorado statute specifically prohibits or regulates induced seismicity. If individuals are injured by seismicity induced in Colorado, they could claim compensation under trespass, negligence or nuisance theories of liability, but Colorado courts are unlikely to apply strict liability to the activities that can induce earthquakes.

Institute of Ural Branch of Russian Academy of Sciences Cover: Evolution of the sinkhole in Berezniki-1 potash mine (Perm region, Russia) and associated seismicity Backcover: Cross-section of fossilized Permian tree conserved in salt layer Printed by Inter-YES ltd, Perm, Russia SEISMICITY ASSOCIATED WITH KARST IN FLOODED SALT MINES -511 -

Over the past three decades, a significant number of small-magnitude and shallow earthquakes have occurred in the Western Canada Sedimentary Basin and are located along its western flank near areas of oil and gas production. One of the better documented examples is the swarm of earthquakes associated with the Strachan field, in the Alberta foothills. A model based on Segall's poroelastic theory is developed to account for the occurrence of earthquakes below the Strachan reservoir. Using this methodology, we show that the earthquake of 19 October 1996, underneath the Strachan field, was most probably triggered by gas extraction. The numerical model also implies that gas extraction would cause subsidence and localized changes in in situ stress magnitudes. There is a strong correlation between rates of production and the number of seismic events, but the onset of major seismic activity postdates the commencement of production by approximately 5 years. Poroelastic modelling can account neatly for this observed delay. The modelled stress changes due to gas extraction point to a regime which favours reverse or thrust faulting that is compatible with stress magnitude measurements in the area. The proposed mechanism involves volume changes which decrease the vertical stress S v and increase the larger horizontal stress S Hmax . The mean stress increase beneath the reservoir appears to be small, but increasing the deviatoric stress permits Mohr-Coulomb failure. As a result, the initially high rate and long history of gas extraction appear likely to be the main trigger for the seismicity beneath the Strachan field.

The Groningen gas field in the Netherlands is one of the largest gas fields of Europe and has been in production since the 60’s. Due to the progressive depletion of the reservoir, induced seismic activity has increased in recent years. In 2012, an earthquake of magnitude 3.6 initiated further research in prediction and management of risks related to man-induced earthquakes.

The work reported here deals with the derivation of spatially distributed Shear Wave Velocity (Vs) for the upper 30 m of the subsurface column (Vs30). The Geological Survey of the Netherlands and Deltares combined a beta version of the GeoTOP model of the area and seismic cone penetration tests (SECPT) into a Vs30 model of the area covering the gas field. The GeoTOP model is a 3D voxel model, in which each voxel is attributed with lithostratigraphy and lithological classes (peat, clay, fine sand, etc.). The modelling procedure of GeoTOP starts with the modelling of top and bottom of each stratigraphical unit. Next, the 3D volume in between top and bottom (voxels) is filled with lithoclasses using geostatistical indicator simulation routines. This results in a 3D model in which each voxel has attributes describing the lithostratigraphial unit and the most likely lithoclass.

60 SECPT’s were used to derive statistical distributions (with mean and standard deviation) of Vs for each combination of lithostratigraphical unit and lithoclass. In this way it was possible to assign a specific Vs to each voxel in the model.

For each voxel in the stack of voxels that covers the upper 30 m (i.e. 60 voxels), a Vs value was randomly drawn from the statistical distribution of the lithostratigraphical – lithoclass combination it belongs to. The Vs30 for each voxelstack is then calculated using the harmonic mean of the Vs of the 60 voxels. By repeating this procedure 100 times, the uncertainty in Vs30 was determined.

Using the above described procedure we were able to delineate zones with distinct Vs30 characteristics: areas containing predominantly soft Holocene deposits with low Vs30 and areas with predominantly stiff Pleistocene deposits with high Vs30. Also the uncertainty in Vs30 could be quantified. This is a huge improvement compared to the previously used Vs30, which was one value for the entire gas field. The Vs30 will be used as input for site amplification predictions.

A spatially localized seismic sequence originated few tens of kilometres offshore the Mediterranean coast of Spain, close to the Ebro river delta, starting on 2013 September 5, and lasting at least until 2013 October. The sequence culminated in a maximal moment magnitude Mw 4.3 earthquake, on 2013 October 1. The most relevant seismogenic feature in the area is the Fosa de Amposta fault system, which includes different strands mapped at different distances to the coast, with a general NE–SW orientation, roughly parallel to the coastline. However, no significant known historical seismicity has involved this fault system in the past. The epicentral region is also located near the offshore platform of the Castor project, where gas is conducted through a pipeline from mainland and where it was recently injected in a depleted oil reservoir, at about 2 km depth. We analyse the temporal evolution of the seismic sequence and use full waveform techniques to derive absolute and relative locations, estimate depths and focal mechanisms for the largest events in the sequence (with magnitude mbLg larger than 3), and compare them to a previous event (2012 April 8, mbLg 3.3) taking place in the same region prior to the gas injection. Moment tensor inversion results show that the overall seismicity in this sequence is characterized by oblique mechanisms with a normal fault component, with a 30? low-dip angle plane oriented NNE–SSW and a subvertical plane oriented NW–SE. The combined analysis of hypocentral location and focal mechanisms could indicate that the seismic sequence corresponds to rupture processes along shallow low-dip surfaces, which could have been triggered by the gas injection in the reservoir, and excludes the activation of the Amposta fault, as its known orientation is inconsistent with focal mechanism results. An alternative scenario includes the iterated triggering of a system of steep faults oriented NW–SE, which were identified by prior marine seismics investigations.

Cover: Evolution of the sinkhole in Berezniki-1 potash mine (Perm region, Russia) and associated seismicity Backcover: Cross-section of fossilized Permian tree conserved in salt layer Verkhnekamskoye potash deposit (VPD) is the only exploited potash deposit in Russia. It is second in the world on reserves after the Saskatchewan deposit in Canada. The first mine at the VPD was brought into production in 1933. Intensive mining began in the middle of the 1980s, when 6 mines were in operation. Ores are extracted from potash beds at the depths of 200-400 meters below surface. There is no evidence of any natural seismic activity in the vicinity of the potash mines prior to the beginning of mining. Large induced seismic events with magnitudes 2.6-4.7 that were felt by residents appeared in the 1990s. The epicentres of these earthquakes were within the VPD boundaries. Since 1995 underground monitoring systems were installed in all 6 working potash mines. Fifteen years of monitoring enabled accurate observation of induced seismicity at mines.

We show that microseismic events—earthquakes with small magnitudes—can be fruitfully used to gain insight into the properties of the fracture network of large-scale porous media, such as oil, gas, and geothermal reservoirs. As an example, we analyze extensive data for the Geysers geothermal field in northeast California. Injection of cold water into the reservoir to produce steam leads to microseismic events. It is demonstrated that the analysis can also lead to insight into whether the fractures are of tectonic type or induced by injection of cold water. To demonstrate this we estimate, using the catalogue of the microseismic events, the fractal dimension D f of the spatial distribution of hypocenters of the events in three seismic clusters associated with the injection of cold water into the field, as well as the b values in the Gutenberg-Richter frequency-magnitude distribution. The fractal dimensions are all in a narrow range centered around D f 2.57 ± 0.06, comparable to the measured fractal dimension of fracture sets in the greywacke reservoir rock. For most cases the b values are about b 1.3 ± 0.1, consistent with the Aki relation, D f = 2b. Both D f and b are significantly higher than those commonly observed for regional tectonic seismicity or aftershock sequences for which D f ≈ 2 and b ≈ 1 are typical. Our results do not imply that no tectonic triggering exists in the reservoir, but rather that the overpressure allows the activation of less favorably oriented fractures that produce an increase in both b and D f. The estimate D f ≈ 2 for tectonic seismicity has been interpreted as indicating that most tectonic events occur on the subset of near-vertical faults—because they have lower normal stress—or that they occur on the backbone of the fracture and fault network, the multiply connected part of the network that enables finite shear strain. Our results lend support to the latter. The results that the entire fracture network, and not just its backbone, is active at the Geysers indicate that the seismicity is not a result of the triggered release of tectonic stress, but is induced by the release of local stress concentrations, driven by thermal contraction that is not constrained by friction. The possible implication for hydraulic fracturing—so-called fracking—is also briefly discussed.

Estimation of the spatial variation of the b-value of the Gutenberg-Richter relationship is important for both the general interpretation of the mechanism of rock mass response and seismic hazard assessment. The interpretation of b-value as a parameter of rock mass response is discussed in this paper. The methods applied to evaluate the spatial variation of the b-value and the algorithm for obtaining the magnitude of completeness and b-value for subsets of data is presented with some verification analyses. The algorithms presented in the paper enables the automation of a spatial evaluation of the b-value.

A seismological model is developed for earthquakes induced by subsurface reservoir volume Q2 changes. The approach is based on the work of Kostrov (1974) and McGarr (1976) linking total strain to the summed seismic moment in an earthquake catalog. We refer to the fraction of the total strain expressed as seismic moment as the strain partitioning function,. A probability distribution for total seismic moment as a function of time is derived from an evolving earthquake catalog. The moment distribution is taken to be a Pareto Sum Distribution with confidence bounds estimated using approximations given by Zaliapin et al. (2005). In this way available seismic moment is expressed in terms of reservoir volume change and hence compaction in the case of a depleting reservoir. The Pareto Sum Distribution for moment and the Pareto Distribution underpinning the Gutenberg-Richter Law are sampled using Monte Carlo methods to simulate synthetic earthquake catalogs for subsequent estimation of seismic ground motion hazard. We demonstrate the method by applying it to the Groningen gas field. A compaction model for the field calibrated using various geodetic data allows reservoir strain due to gas extraction to be expressed as a function of both spatial position and time since the start of production. Fitting with a generalized logistic function gives an empirical expression for the dependence of on reservoir compaction. Probability density maps for earthquake event locations can then be calculated from the compaction maps. Predicted seismic moment is shown to be strongly dependent on planned gas production.

“Frackquakes” that are man-made injection-induced earthquakes increase sharply in the booming areas of oil and gas field development in the United States of America.  The hydraulic fracturing practices usually trigger only tiny earthquakes (or rather “acoustic emissions(AE)” in other words) smaller than magnitude 2 in tight impermeable shale layers. However, massive underground wastewater injections into permeable formations are more likely to drive widespread underground pore pressure fluctuation that may provoke instability of existing faults and trigger larger “injection-induced earthquakes”.  The growing human activities such as oil, gas and other mineral developments, geothermal developments, large-scale reservoirs, irrigation and drainage system and groundwater management affect the widespread underground pore pressures and increase the risk of induced seismicity.  The largest man-made induced earthquake is the 2008 M8 Sichuan earthquake triggered by a dam reservoir in a large-scale fault zone in China. The 2011 M9 Great East Japan earthquake was a natural fluid injection-induced earthquake. The M7-8 New Madrid earthquakes shaked central United States in 1811 and in 1812 reactivating an old mid-continental rift structure “Reelfoot rift”.  The hydraulic fracturing and wastewater injection should be cautious not to reactivate another old mid-continental rift structure “Southern Oklahoma Aulacogen”.
The Griffith inclusion model of fault, the effective stress control of hydraulic fracturing and the Coulomb failure stress on fault are discussed to analyze the mechanism of induced earthquakes. The “man-made” induced earthquake is actually an artificially accelerated natural earthquake. The geological and geophysical survey of natural critical faults, estimation of underground stress state, properties of underground rocks and investigation of underground fluids and groundwater regime are important to minimize the risk of induced seismicity.