Frequency-dependent rupture process, stress change, and seismogenic mechanism of the 25 April 2015 Nepal Gorkha M w 7.8 earthquake

Yin, Jiuxun; Yao, Huajian; Yang, Hongfeng; Liu, Jing; Qin, Weize; Zhang, Haijiang

doi:10.1007/s11430-016-9006-0

Cited by 22 publications

(17 citation statements)

References 66 publications

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“…The synthetic second peak developed in Cases 2 through 4 strongly disfavors coseismic rupture on the shallower (i.e., southwestern) ramp, at least in the area to the west of the KKN4 station. That inference is further supported by the fact that sources of high‐frequency seismic radiation have been imaged in the area near the lower kink but not near the upper kink where the shallow ramp and the flat decollement intersect (e.g., Avouac et al, ; Yin et al, ). KKN4 was the only bedrock‐based recording sufficiently free of path and site effects for our purposes, and its recorded ground velocity pulse mainly reflects the rupture occurring below and to the west of KKN4.…”

Section: Discussionmentioning

confidence: 94%

“…Journal of Geophysical Research: Solid Earth the area near the lower kink but not near the upper kink where the shallow ramp and the flat decollement intersect (e.g., Avouac et al, 2015;Yin et al, 2017). KKN4 was the only bedrock-based recording sufficiently free of path and site effects for our purposes, and its recorded ground velocity pulse mainly reflects the rupture occurring below and to the west of KKN4.…”

Section: 1029/2018jb016602mentioning

confidence: 99%

“…The event had a pulse‐like rupture mode (Galetzka et al, ; Yue et al, ) with a slip pulse of ~20 km in spatial width and ~6 s in temporal duration (Galetzka et al, ). Moreover, depth‐ and frequency‐varying rupture properties (Denolle et al, ; Yin et al, ; Yue et al, ) have been observed, with patterns broadly resembling those seen on subduction megathrusts (Yao et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

2019

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The 15 April 2015 Mw 7.8 Nepal Gorkha earthquake occurred on a shallowly dipping portion of the Main Himalayan Thrust (MHT). Notable features of the event include (1) the dominance of a slip pulse of about 6‐s duration that unlocked the lower edge of the MHT and (2) the near‐horizontal fault geometry, which, combined with proximity of the free surface, allows surface‐reflected phases to break the across‐fault symmetries of the seismic wavefield. Our dynamic rupture simulations in an elastoplastic medium yield earthquake parameters comparable to those deduced from kinematic inversions, including seismic moment and rupture velocity. The simulations reproduce pulse‐like behavior predicting pulse widths in agreement with those kinematic studies and supporting an interpretation in which the pulse‐like time dependence of slip is principally controlled by rupture geometry. This inference is strongly supported by comparison of synthetic ground velocity with the near‐field high‐rate GPS recording at station KKN4, which shows close agreement in pulse width, amplitude, and pulse shape. That comparison also constrains the updip extent of rupture and disfavors significant coseismic slip on the shallow ramp segment. Over most of the rupture length, the simulated rupture propagates at a near‐constant maximum velocity (~90% of the S wave speed) that is controlled by the antiplane geometry and off‐fault plastic yielding. Simulations also reveal the role of reflected seismic waves from the free surface, which may have contributed ~30% elongation of the slip pulse, and show the potential for significant free‐surface interaction effects in shallow events of similar geometry.

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Section: Discussionmentioning

confidence: 94%

Section: 1029/2018jb016602mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

2019

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“…Moment tensor solutions show that this earthquake was a nearly pure double-couple reverse faulting event, with the fault plane estimated to have a strike of 293°, a dip angle of 7-10°, and a rake of 95-100° (Avouac et al, 2015;Galetzka et al, 2015;Wei et al, 2018). The final slip distribution and rupture speed obtained from kinematic inversions and backprojection methods consistently show that this earthquake had a relative simple rupture pattern with an average speed of 2.8-3.2 km/s Grandin et al, 2015;Lay et al, 2016;Liu et al, 2016;Wei et al, 2018;Yagi & Okuwaki, 2015;Yin et al, 2017;Yue et al, 2016) (Figure 1a and Table 1). A number of seismic and geodetic apparatus, which have been installed in this region over past 20 years, provide a unique opportunity to investigate the rupture process of this event and the frictional properties of the seismogenic fault.…”

Section: Introductionmentioning

confidence: 82%

Constraining Frictional Properties on Fault by Dynamic Rupture Simulations and Near‐Field Observations

Weng

Yang

2018

JGR Solid Earth

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Frictional properties of seismogenic faults play critical roles in earthquake generation and rupture propagation. Although laboratory measurements have well revealed the frictional parameters of a variety of rock samples, those on seismogenic faults remain difficult to determine due to the strong trade‐off between critical slip‐weakening distance (d0) and strength drop. Here we conduct dynamic rupture simulations to determine the frictional parameters on the fault where the 2015 Mw7.8 Nepal earthquake occurred, with constraints from near‐field seismic and geodetic observations, and kinematic source models. By utilizing different trade‐off patterns of source parameters and multiple observations for the first time, we can determine the frictional parameters of the seismogenic fault. The best fit dynamic model yields a d0value of ~0.6 m, in contrast to the previous kinematical estimation of ~5 m (Galetzka et al., 2015, https://doi.org/10.1126/science.aac6383). The average fracture energy of this event is trueGC¯≃1.4×106 J/m2. Such approach can be used to determine the frictional parameters on seismogenic faults, which could serve for seismic hazard assessment by predicting ground motion from dynamic rupture simulations.

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“…The spatiotemporal distribution of seismic energy bursts from ImCS‐BP potentially brings insight on physical properties on the fault interface. Many backprojection studies of the large subduction zone thrust earthquakes, such as the M w 9.3 2004 and M w 8.8 2005 Sumatra, the M w 9.0 2011 Japan, the M w 8.8 2010 and M w 8.3 2015 southern Chile (Lay et al, ; Wang & Mori, ; Yao et al, , ; Yin et al, ), the M w 8.0 2007 Peru (Sufri et al, ), and in a large continental subduction zone such as the M w 7.9 2015 Nepal (Yin et al, ; Yue et al, ), reveal clear systematic differences between the frequency content of the updip and downdip regions. Our results from ImCS‐BP are consistent with previous studies that identify LF radiation in the updip part and HF radiation in the downdip region of the megathrust earthquakes.…”

Section: Discussionmentioning

confidence: 99%

Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the M_w 8.3 Illapel Earthquake, Chile

2018

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We develop a methodology that combines compressive sensing backprojection (CS‐BP) and source spectral analysis of teleseismic P waves to provide metrics relevant to earthquake dynamics of large events. We improve the CS‐BP method by an autoadaptive source grid refinement as well as a reference source adjustment technique to gain better spatial and temporal resolution of the locations of the radiated bursts. We also use a two‐step source spectral analysis based on (i) simple theoretical Green's functions that include depth phases and water reverberations and on (ii) empirical P wave Green's functions. Furthermore, we propose a source spectrogram methodology that provides the temporal evolution of dynamic parameters such as radiated energy and falloff rates. Bridging backprojection and spectrogram analysis provides a spatial and temporal evolution of these dynamic source parameters. We apply our technique to the recent 2015 Mw 8.3 megathrust Illapel earthquake (Chile). The results from both techniques are consistent and reveal a depth‐varying seismic radiation that is also found in other megathrust earthquakes. The low‐frequency content of the seismic radiation is located in the shallow part of the megathrust, propagating unilaterally from the hypocenter toward the trench while most of the high‐frequency content comes from the downdip part of the fault. Interpretation of multiple rupture stages in the radiation is also supported by the temporal variations of radiated energy and falloff rates. Finally, we discuss the possible mechanisms, either from prestress, fault geometry, and/or frictional properties to explain our observables. Our methodology is an attempt to bridge kinematic observations with earthquake dynamics.

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Frequency-dependent rupture process, stress change, and seismogenic mechanism of the 25 April 2015 Nepal Gorkha M w 7.8 earthquake

Cited by 22 publications

References 66 publications

Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

Constraining Frictional Properties on Fault by Dynamic Rupture Simulations and Near‐Field Observations

Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the M_w 8.3 Illapel Earthquake, Chile

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Frequency-dependent rupture process, stress change, and seismogenic mechanism of the 25 April 2015 Nepal Gorkha M w 7.8 earthquake

Cited by 22 publications

References 66 publications

Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

Geometric Controls on Pulse‐Like Rupture in a Dynamic Model of the 2015 Gorkha Earthquake

Constraining Frictional Properties on Fault by Dynamic Rupture Simulations and Near‐Field Observations

Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the Mw 8.3 Illapel Earthquake, Chile

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Spatial and Temporal Evolution of Earthquake Dynamics: Case Study of the M_w 8.3 Illapel Earthquake, Chile