The 2012 Brawley swarm triggered by injection-induced aseismic slip

Wei, Shengji; Avouac, Jean Philippe; Hudnut, K. W.; Donnellan, Andrea; Parker, Jay; Graves, Robert; Helmberger, Donald V.; Fielding, E. J.; Liu, Zhen; Cappa, Frédéric; Eneva, Mariana

doi:10.1016/j.epsl.2015.03.054

Cited by 167 publications

(215 citation statements)

References 31 publications

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“…It is important to note, however, that a large percentage of the permeability enhancement that accompanies well stimulation may be aseismic, as has been directly observed during a decameter-scale injection experiment described by Guglielmi et al (2015) and in seismic data recorded during hydraulic fracturing (Das & Zoback, 2011). Further evidence of aseismic slip has been inferred at the high-temperature Salton Sea geothermal field in southern California from a combined geodetic and seismic data set (Wei et al, 2015). Riffault et al (2018) have also demonstrated that, in some cases, permeability enhancement may not be coupled to detectable seismic slip at all.…”

Section: Mechanisms Of Microseismicity and Permeability Enhancementmentioning

confidence: 79%

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

Hopp

Sewell

Mroczek

et al. 2019

Geochem Geophys Geosyst

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Fluid injection into the Earth's crust can induce seismic events that cause damage to local infrastructure but also offer valuable insight into seismogenesis. The factors that influence the magnitude, location, and number of induced events remain poorly understood but include injection flow rate and pressure as well as reservoir temperature and permeability. The relationship between injection parameters and injection‐induced seismicity in high‐temperature, high‐permeability reservoirs has not been extensively studied. Here we focus on the Ngatamariki geothermal field in the central Taupō Volcanic Zone, New Zealand, where three stimulation/injection tests have occurred since 2012. We present a catalog of seismicity from 2012 to 2015 created using a matched‐filter detection technique. We analyze the stress state in the reservoir during the injection tests from first motion‐derived focal mechanisms, yielding an average direction of maximum horizontal compressive stress (SHmax) consistent with the regional NE‐SW trend. However, there is significant variation in the direction of maximum compressive stress (σ1), which may reflect geological differences between wells. We use the ratio of injection flow rate to overpressure, referred to as injectivity index, as a proxy for near‐well permeability and compare changes in injectivity index to spatiotemporal characteristics of seismicity accompanying each test. Observed increases in injectivity index are generally poorly correlated with seismicity, suggesting that the locations of microearthquakes are not coincident with the zone of stimulation (i.e., increased permeability). Our findings augment a growing body of work suggesting that aseismic opening or slip, rather than seismic shear, is the active process driving well stimulation in many environments.

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Section: Mechanisms Of Microseismicity and Permeability Enhancementmentioning

confidence: 79%

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

Hopp

Sewell

Mroczek

et al. 2019

Geochem Geophys Geosyst

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“…The Dianjiang earthquake and other shallow earthquakes (e.g., Brune & Allen, 1967;Wei et al, 2015) indicate that earthquakes can still nucleate in the shallow crust. The stress at shallow depth is considered quite different from the seismogenic depth range.…”

Section: Discussionmentioning

confidence: 99%

An Extremely Shallow M_w4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction

Qian

Chen

Luo³

et al. 2019

Geophysical Research Letters

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Triggered or induced earthquakes have been widely reported as resulting from various human activities, yet seismicity triggered by small-scale infrastructure construction is rare. Here, we report on an investigation of an extremely shallow M w 4.1 earthquake which occurred on 11 August 2016 in the Sichuan Basin (China), a region with historically low seismicity. Our seismic waveform analyses indicate an almost pure thrust focal mechanism at a centroid depth of~1 km. Furthermore, 18 Sentinel-1 synthetic aperture radar interferograms, stacked to obtain subcentimeter accuracy, reveal up to 3 cm line-of-sight deformation which overlaps with an automotive testing site constructed in 2014. Removal of 10 m of a surface rock layer during the construction may have produced an unloading effect and resulted in up to 0.11 MPa Coulomb stress changes on a blind fault, larger than the 0.01 MPa threshold typically invoked in studies of tectonic earthquakes. However, the delayed triggering still requires further investigation. Plain Language SummaryWhile induced earthquakes in the shallow part of the crust have been observed globally, a remaining knowledge gap is whether small-scale infrastructure construction can trigger earthquakes or not. We investigate these questions on an extremely shallow M w 4.1 earthquake in the eastern Sichuan Basin (China). To determine earthquake source parameters, we combine seismological data with satellite imaging. We find this thrust event ruptured at the depth of~1 km, located just beneath an automotive testing site constructed in 2014. Crucially, we note the testing site construction involved removal of a large volume of surface rock. We further analyze the stress changes produced by the unloading of the surface rock. We find a possible triggering relationship between the infrastructure construction and the occurrence of this shallow earthquake. Our results thus shed new light on the causes of shallow earthquakes associated with small-scale infrastructure construction.

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“…Thus, another interpretation might be that the blank area corresponds with a barrier encountered within the source area that was broken leading to the mainshock. Actually this gap is an interesting phenomenon, as pointed out in Wei et al (2013Wei et al ( , 2015; this could be caused by the rupture asperity of the big events in the sequence.…”

Section: Data From the Rsh Stationmentioning

confidence: 96%

Rushan earthquake swarm in eastern China and its indications of fluid-triggered rupture

Zheng

et al. 2017

Earthq Sci

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An extraordinary earthquake swarm occurred at Rushan on the Jiaodong Peninsula from October 1, 2013, onwards, and more than 12,000 aftershocks had been detected by December 31, 2015. All the activities of the whole swarm were recorded at the nearest station, RSH, which is located about 12 km from the epicenter. We examine the statistical characteristics of the Rushan swarm in this paper using RSH station data to assess the arrival time difference, t S À P , of Pg and Sg phases. A temporary network comprising 18 seismometers was set up on May 6, 2014, within the area of the epicenter; based on the data from this network and use of the double difference method, we determine precise hypocenter locations. As the distribution of relocated sources reveals migration of seismic activity, we applied the mean-shift cluster method to perform clustering analysis on relocated catalogs. The results of this study show that there were at least 16 clusters of seismic activities between May 6, 2014, and June 30, 2014, and that each was characterized by a hypocenter spreading process. We estimated the hydraulic diffusivity, D, of each cluster using envelope curve fitting; the results show that D values range between 1.2 and 3.5 m 2 /d and that approximate values for clusters on the edge of the source area are lower than those within the central area. We utilize an epidemic-type aftershock sequence (ETAS) model to separate external triggered events from self-excited aftershocks within the Rushan swarm. The estimated parameters for this model suggest that a = 1.156, equivalent to sequences induced by fluid-injection, and that the forcing rate (l) implies just 0.15 events per day. These estimates indicate that around 3% of the events within the swarm were externally triggered. The fact that variation in l is synchronous with swarm activity implies that pulses in fluid pressure likely drove this series of earthquakes.

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The 2012 Brawley swarm triggered by injection-induced aseismic slip

Cited by 167 publications

References 31 publications

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

An Extremely Shallow M_w4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction

Rushan earthquake swarm in eastern China and its indications of fluid-triggered rupture

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The 2012 Brawley swarm triggered by injection-induced aseismic slip

Cited by 167 publications

References 31 publications

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

Seismic Response to Injection Well Stimulation in a High‐Temperature, High‐Permeability Reservoir

An Extremely Shallow Mw4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction

Rushan earthquake swarm in eastern China and its indications of fluid-triggered rupture

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An Extremely Shallow M_w4.1 Thrust Earthquake in the Eastern Sichuan Basin (China) Likely Triggered by Unloading During Infrastructure Construction