Microseismic Activity in the Last Five Months before the
            <i>M</i>
            <sub>w</sub>
             7.9 Wenchuan Earthquake

Ruan, Xiang; Meng, Xiaofeng; Peng, Zhigang; Feng, Li; Xie, Rongan

doi:10.1785/0120160332

Cited by 8 publications

(8 citation statements)

References 57 publications

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“…Moreover, by visually examining the spectrogram ~1.5 hr before the mainshock (Figure S4), we confirm that no immediate foreshocks were observed. This observation adds to a growing body of evidences that no clear foreshock activity exists before moderate and large intraplate earthquakes (e.g., Doi & Kawakata, ; Ruan et al, ; C. Wu et al, ; Yang et al, ). However, there were also several mainshocks in eastern North American Plate preceded by foreshock activity, including several felt tremors days before the 1886 M 6.9–7.3 Charleston earthquake (Dutton, ) and a M 4.7 event 2 days before the 1988 M 5.9 Saguenay, Quebec, earthquake (Somerville et al, ).…”

Section: Interpretations and Discussionsupporting

confidence: 59%

Section: Foreshock Activitysupporting

confidence: 58%

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Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake

2018

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The 2011 Mw 5.7 Virginia earthquake and subsequent dense deployment provide us an unprecedented opportunity to study in detail an earthquake sequence within stable continental United States. Here we apply the waveform‐based matched filter technique to obtain more complete earthquake catalogs around the origin time of the Virginia mainshock. With the enhanced earthquake catalogs, we conclude that no foreshock activity existed prior to the Virginia mainshock. The b value map shows significant variations across the aftershock zone, suggesting strong heterogeneity in stress distribution or crustal material in the study region. We also investigate multiple earthquake triggering mechanisms, including static and dynamic triggering, afterslip, and atmospheric pressure changes. We find that dynamic triggering best explains aftershock distributions close to the mainshock's rupture plane, while the activation of off‐fault seismicity is consistent with static Coulomb stress changes. Moreover, an off‐fault earthquake swarm occurred as the Category 2 Hurricane Irene passed by the aftershock zone 5 days after the mainshock, which might be promoted by stress changes associated with atmospheric pressure drop. Our observations suggest that multiple mechanisms may be responsible for triggering aftershocks following one earthquake.

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Section: Interpretations and Discussionsupporting

confidence: 59%

Section: Foreshock Activitysupporting

confidence: 58%

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake

2018

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“…This method utilizes waveforms of existing events as templates and scans through continuous waveforms to detect additional events with high similarities (Gibbons & Ringdal, ; Shelly et al, ). This method has been widely used to detect early aftershocks following large mainshocks (A. Kato & Obara, ; Lengline et al, ; Peng & Zhao, ; Wu et al, ; H. Yang et al, ; Yao et al, ), as well as preceding foreshocks (A. Kato et al, , ; Ruan et al, ; Walter et al, ) and remotely triggered seismicity (W. Wang et al, ; Yao et al, ), resulting in a few to tens of times more events than listed in the standard earthquake catalogs. Slinkard et al () used waveform correlation with a composite regional network to detect the Wenchuan aftershock sequence and identified more than 6,000 additional events in the 3 months following the Wenchuan mainshock.…”

Section: Introductionmentioning

confidence: 99%

“…Yang et al, 2009;Yao et al, 2017), as well as preceding foreshocks (A. Kato et al, 2016Kato et al, , 2012Ruan et al, 2017;Walter et al, 2015) and remotely triggered seismicity (W. Wang et al, 2015;Yao et al, 2015), resulting in a few to tens of times more events than listed in the standard earthquake catalogs. Slinkard et al (2016) used waveform correlation with a composite regional network to detect the Wenchuan aftershock sequence and identified more than 6,000 additional events in the 3 months following the Wenchuan mainshock.…”

Section: Introductionmentioning

confidence: 99%

Evolution and Distribution of the Early Aftershocks Following the 2008 Mw 7.9 Wenchuan Earthquake in Sichuan, China

et al. 2018

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Using seismic data recorded by a dense temporary seismic array, we apply a waveform matched‐filter technique and obtain an early aftershock catalog around the mainshock rupture zone of the 2008 Wenchuan, Sichuan, China, earthquake. Specifically, we use 1,273 events in a relocated aftershock catalog as templates and scan through the waveforms within 7 days following the mainshock. We obtain up to ∼5.3 and ∼10 times more aftershocks than the standard and relocated catalogs, respectively. We find that early aftershocks mostly occurred below 10 km depth, downdip to large coseismic slip areas. Early aftershocks also show minor along‐strike migration with time since the mainshock, indicating triggering of afterslip following the mainshock. From the epicentral region to Beichuan where the mainshock slip was primarily reverse faulting, early aftershocks illustrated the Yingxiu‐Beichuan and Guanxian‐Jiangyou faults as high‐angle listric feature and rooted to a gentle dipping plane at the depth of ∼20 km. The aftershocks in the northeast segment of the Longmen Shan faults mostly occurred along a near‐vertical dipping fault, consistent with the primary strike‐slip component of mainshock slip in this region. In addition, differences in early and long‐term aftershock distribution indicate significant postseismic deformation along the conjugate Xiaoyudong fault. Our results help to illuminate the deep geometry of the Longmen Shan fault zone and the early evolution after the Wenchuan mainshock, which provides additional constraints to the mechanism of plateau uplifting.

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“…WMFT has been successfully applied to detect missing earthquakes before (e.g. Kato et al 2012;Kato & Nakagawa 2014;Walter et al 2015;Ruan et al 2017) and after large shallow earthquakes (Peng & Zhao 2009;Meng et al 2013;Meng & Peng 2014), as well as lowfrequency earthquakes within deep tectonic tremors (e.g. Shelly et al 2007;Brown et al 2008;Shelly & Hardebeck 2010;Tang et al 2010;Frank & Shapiro 2014;Chao et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

Peng

Yao

et al. 2018

Geophysical Journal International

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The 2015 M w 7.5 Hindu Kush earthquake occurred at a depth of 213 km beneath the Hindu Kush region of Afghanistan. While many early aftershocks were missing from the global earthquake catalogues, this sequence was recorded continuously by eight broad-band stations within 500 km. Here we use a waveform matching technique to systematically detect earthquakes around the main shock. More than 3000 events are detected within 35 d after the main shock, as compared with 42 listed in the Advanced National Seismic System catalogue (or 196 in the International Seismological Centre catalogue). The aftershock sequence generally follows the Omori's law with a decay constant p = 0.92. We also apply the recently developed double-pair double-difference technique to relocate all detected aftershocks. Most of them are located to the west of the hypocentre of the main shock, consistent with the westward propagation of the main-shock rupture. The aftershocks outline a nearly vertical southward dipping plane, which matches well with one of the nodal planes of the main shock. We conclude that the aftershock sequence of this intermediate-depth earthquake shares many similarities with those for shallow earthquakes and infer that there are some common mechanisms responsible for shallow and intermediate-depth earthquakes.

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Microseismic Activity in the Last Five Months before the M _w 7.9 Wenchuan Earthquake

Cited by 8 publications

References 57 publications

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake

Evolution and Distribution of the Early Aftershocks Following the 2008 Mw 7.9 Wenchuan Earthquake in Sichuan, China

Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

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Microseismic Activity in the Last Five Months before the M w 7.9 Wenchuan Earthquake

Cited by 8 publications

References 57 publications

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 Mw 5.7 Virginia Earthquake

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 Mw 5.7 Virginia Earthquake

Evolution and Distribution of the Early Aftershocks Following the 2008 Mw 7.9 Wenchuan Earthquake in Sichuan, China

Abundant aftershock sequence of the 2015 Mw7.5 Hindu Kush intermediate-depth earthquake

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Resources

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Microseismic Activity in the Last Five Months before the M _w 7.9 Wenchuan Earthquake

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake

Foreshocks, b Value Map, and Aftershock Triggering for the 2011 M_w 5.7 Virginia Earthquake