Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake

Avouac, Jean Philippe; Meng, Lingsen; Wei, Shengji; Wang, Teng; Ampuero, Jean‐Paul

doi:10.1038/ngeo2518

Cited by 429 publications

(342 citation statements)

References 33 publications

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“…This is also consistent with Evangelidis & Kao (2013) who imaged a high-frequency (HF) source at this depth and location which they relate to rupture termination or geometric complexity. A similar trend was observed in the location of the HF seismic radiation sources in the 2015 Gorkha Earthquake, Nepal (Avouac et al 2015); Elliott et al (2016) show that the HF sources are co-located with a change in dip of the fault plane, though in that case, they were in the middle of the rupture zone.…”

Section: Fault Geometrysupporting

confidence: 48%

Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Mackenzie¹,

Elliott²,

Altunel

et al. 2016

Geophys. J. Int.

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S U M M A R YThe 2011 October 23 M W 7.1 Van earthquake in eastern Turkey caused ∼600 deaths and caused widespread damage and economic loss. The seismogenic rupture was restricted to 10-25 km in depth, but aseismic surface creep, coincident with outcrop fault exposures, was observed in the hours to months after the earthquake. We combine observations from radar interferometry, seismology, geomorphology and Quaternary dating to investigate the geological slip rate and seismotectonic context of the Van earthquake, and assess the implications for continuing seismic hazard in the region. Transient post-seismic slip on the upper Van fault started immediately following the earthquake, and decayed over a period of weeks; it may not fully account for our long-term surface slip-rate estimate of ≥0.5 mm yr −1 . Post-seismic slip on the Bostaniçi splay fault initiated several days to weeks after the main shock, and we infer that it may have followed the M W 5.9 aftershock on the 9th November. The Van earthquake shows that updip segmentation can be important in arresting seismic ruptures on dip-slip faults. Two large, shallow aftershocks show that the upper 10 km of crust can sustain significant earthquakes, and significant slip is observed to have reached the surface in the late Quaternary, so there may be a continuing seismic hazard from the upper Van fault and the associated splay. The wavelength of folding in the hanging wall of the Van fault is dominated by the structure in the upper 10 km of the crust, masking the effect of deeper seismogenic structures. Thus, models of subsurface faulting based solely on surface folding and faulting in regions of reverse faulting may underestimate the full depth extent of seismogenic structures in the region. In measuring the cumulative post-seismic offsets to anthropogenic structures, we show that Structure-from-Motion can be rapidly deployed to create snapshots of postseismic displacement. We also demonstrate the utility of declassified Corona mission imagery (1960s-1970s) for geomorphic mapping in areas where recent urbanization has concealed the geomorphic markers.

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Section: Fault Geometrysupporting

confidence: 48%

Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Mackenzie¹,

Elliott²,

Altunel

et al. 2016

Geophys. J. Int.

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“…Finally, the rupture speed increased to ∼3.5 km s −1 and split into two segments, swerving around the rupture zone of largest aftershock, which failed 18 days later. The average rupture velocity obtained from our back projection is in agreement with the ∼2.72 km s −1 observed by Avouac et al (2015). The multi-pulsed heterogeneous rupture process with time dependent rupture velocity variation, highlighted in our study, closely matches the slow downdip rupture initiation followed by two stages of faster updip ruptures of .…”

Section: Discussionsupporting

confidence: 76%

“…2a) are aligned along an average azimuth of ∼117 • , in agreement with the direction of observed rupture propagation (Supporting Information Movie S1), with higher order deviation from a linear source, pointing to a heterogeneous rupture process. Most of the observed high-frequency (0.2-5 Hz) energy was released north of Katmandu, and is consistent with the slip inversion study of Avouac et al (2015). The cumulative energy distribution on the main-shock fault is bound to the west by its epicentre, and to the east by the largest aftershock (M w 7.3), which occurred on 2015 May 12.…”

Section: B a C K -P Ro J E C T I O N U S I N G M U Lt I P L E T E L Esupporting

confidence: 69%

The 2015 April 25 Gorkha (Nepal) earthquake and its aftershocks: implications for lateral heterogeneity on the Main Himalayan Thrust

Kumar¹,

Singh²,

Mitra³

et al. 2016

Geophys. J. Int.

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S U M M A R YThe 2015 Gorkha earthquake (M w 7.8) occurred by thrust faulting on a ∼150 km long and ∼70 km wide, locked downdip segment of the Main Himalayan Thrust (MHT), causing the Himalaya to slip SSW over the Indian Plate, and was followed by major-to-moderate aftershocks. Back projection of teleseismic P-wave and inversion of teleseismic body waves provide constraints on the geometry and kinematics of the main-shock rupture and source mechanism of aftershocks. The main-shock initiated ∼80 km west of Katmandu, close to the locking line on the MHT and propagated eastwards along ∼117 • azimuth for a duration of ∼70 s, with varying rupture velocity on a heterogeneous fault surface. The main-shock has been modelled using four subevents, propagating from west-to-east. The first subevent (0-20 s) ruptured at a velocity of ∼3.5 km s −1 on a ∼6 • N dipping flat segment of the MHT with thrust motion. The second subevent (20-35 s) ruptured a ∼18 • W dipping lateral ramp on the MHT in oblique thrust motion. The rupture velocity dropped from 3.5 km s −1 to 2.5 km s −1 , as a result of updip propagation of the rupture. The third subevent (35-50 s) ruptured a ∼7 • N dipping, eastward flat segment of the MHT with thrust motion and resulted in the largest amplitude arrivals at teleseismic distances. The fourth subevent (50-70 s) occurred by left-lateral strikeslip motion on a steeply dipping transverse fault, at high angle to the MHT and arrested the eastward propagation of the main-shock rupture. Eastward stress build-up following the mainshock resulted in the largest aftershock (M w 7.3), which occurred on the MHT, immediately east of the main-shock rupture. Source mechanisms of moderate aftershocks reveal stress adjustment at the edges of the main-shock fault, flexural faulting on top of the downgoing Indian Plate and extensional faulting in the hanging wall of the MHT.

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“…As discussed earlier (Section 1), various catastrophic disasters (floods, landslides and other natural calamities) have frequently hit the region, with a death toll of thousands of people each year. The Himalayas are an tectonically active zone and are prone to geological catastrophes (Avouac et al, 2015), as evident from the recent major earthquakes in Nepal and Pakistan/Afghanistan.…”

Section: Severity and Frequency Of Climate Related Disastersmentioning

confidence: 99%

A new Himalayan crisis? Exploring transformative resilience pathways

Satyal

Shrestha

Ojha

et al. 2017

Environmental Development

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Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake

Cited by 429 publications

References 33 publications

Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

The 2015 April 25 Gorkha (Nepal) earthquake and its aftershocks: implications for lateral heterogeneity on the Main Himalayan Thrust

A new Himalayan crisis? Exploring transformative resilience pathways

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Lower edge of locked Main Himalayan Thrust unzipped by the 2015 Gorkha earthquake

Cited by 429 publications

References 33 publications

Seismotectonics and rupture process of theMW 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Seismotectonics and rupture process of theMW 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

The 2015 April 25 Gorkha (Nepal) earthquake and its aftershocks: implications for lateral heterogeneity on the Main Himalayan Thrust

A new Himalayan crisis? Exploring transformative resilience pathways

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Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening

Seismotectonics and rupture process of theM_W 7.1 2011 Van reverse-faulting earthquake, eastern Turkey, and implications for hazard in regions of distributed shortening