Seismic imaging of the Main Frontal Thrust in Nepal reveals a shallow décollement and blind thrusting

Almeida, Rafael; Hubbard, Judith; Liberty, Lee M.; Foster, A. E.; Sapkota, Soma Nath

doi:10.1016/j.epsl.2018.04.045

Cited by 28 publications

(86 citation statements)

References 32 publications

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“…4). They extend 1-10 km south of the Main Himalayan Thrust (Bashyal 1998;Kayastha et al 1998;Almeida et al 2018). The Main Himalayan Thrust has evolved southwards, successively incorporating these blind thrusts as they grow in amplitude and eventually rupture the surface.…”

Section: Twentieth and Twenty-first Century Himalayan Earthquakesmentioning

confidence: 99%

“…Widening the downdip width of the 1934 rupture to 110 km, for example, and retaining the same c. 100 km-long, along-strike length, would require mean slip of 13 m similar to the pre-1934 slip deficit. Almeida et al (2018) speculated that slip in recent earthquakes may have been absorbed south of the Main Frontal Thrust by slip on the blind Bardibas thrust near 86°E.…”

Section: Twentieth and Twenty-first Century Himalayan Earthquakesmentioning

confidence: 99%

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Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Bilham

2019

250

198

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This article summarizes recent advances in our knowledge of the past 1000 years of earthquakes in the Himalaya using geodetic, historical and seismological data, and identifies segments of the Himalaya that remain unruptured. The width of the Main Himalayan Thrust is quantified along the arc, together with estimates for the bounding coordinates of historical rupture zones, convergence rates, rupture propagation directions as constrained by felt intensities. The 2018 slip potential for fifteen segments of the Himalaya are evaluated and potential magnitudes assessed for future earthquakes should these segments fail in isolation or as contiguous ruptures. Ten of these fifteen segments are sufficiently mature currently to host a great earthquake (M w ≥ 8). Fatal Himalayan earthquakes have in the past occurred mostly in the daylight hours. The death toll from a future nocturnal earthquake in the Himalaya could possibly exceed 100 000 due to increased populations and the vulnerability of present-day construction methods. Himalayan geodesy The rate of convergence of India relative to EuroAsia is fundamental to quantifying the anticipated

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Section: Twentieth and Twenty-first Century Himalayan Earthquakesmentioning

confidence: 99%

Section: Twentieth and Twenty-first Century Himalayan Earthquakesmentioning

confidence: 99%

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Bilham

2019

250

198

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“…Many attempts have been made to determine the structure of the Main Himalayan Thrust (MHT) fault in Nepal. Some studies have found evidence that the MHT has a ramp-flat-ramp structure (Nábělek et al, 2009;Wang and Fialko, 2015;Elliott et al, 2016;Wang et al, 2017;Almeida et al, 2018b). A recent study using aftershock data from the Gorkha earthquake argued that instead of a lower ramp, the MHT has a duplex system of steeply dipping faults (Mendoza et al, 2019).…”

Section: Assumed Mht Fault Geometrymentioning

confidence: 99%

Impact of topography on earthquake static slip estimates

et al. 2020

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Our understanding of earthquakes is limited by our knowledge, and our description, of the physics of the Earth. When solving for subsurface fault slip, it is common practice to assume minimum complexity for the Earth's characteristics such as topography, fault geometry and elastic properties. These characteristics are difficult to include in simulations and our knowledge of them is incomplete, leading many to believe that there is minimal advantage to be gained by accounting for these effects. However, 3D structure can be easily included with the newly-developed software package SPECFEM-X, and topography and bathymetry can be measured directly and are well known all over the Earth's surface. Accounting for topography thus seems to be an efficient strategy for incorporating accurate and extensive information into the inverse problem. Here, we explore the impact of topography on static slip estimates, with a particular focus on how topography may impact slip resolution on the fault. We also wonder if the influence of topography can be accounted for by simply using a receiver elevation correction. To this end, we analyze the 2015 M w 7.5 Gorkha, Nepal, and the 2010 M w 8.8 Maule, Chile, earthquakes within a Bayesian framework. The regions affected by these events represent two different types of topography. Chile, which contains both the Peru-Chile trench and the Andes mountains, has a greater elevation range and steeper gradients than Nepal, where the primary topographic feature is the Himalayan mountain range. Additionally, the slip of the continental Nepal event is well constrained, whereas observations are less informative in a subduction context. We show that topography has a non-negligible impact on inferred slip models. Our results suggest that the effect of topography on slip estimates increases with two main factors: poor observational constraints and high elevation gradients. In particular, we find that accounting for topography improves slip resolution where topographic gradients are large and the data is less informative: at depths for the Gorkha event, and near the trench for the Maule

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“…However, it is observed that much of the large surface rupturing earthquakes have cut-across such segmentation and evidence has been reported over large distances (see Bilham, 2019; references therein). Another point to be reckoned with is that the décollement may also have shallower ramps up-dip like the deeper one beneath the High Himalaya that act as geometric barriers to earthquake propagation (Hubbard et al, 2016;Almeida et al, 2018;Bai et al, 2019). The last decade has witnessed a vigorous seismological research in the Himalayas.…”

Section: The Himalayamentioning

confidence: 99%

“…The recent paper on the crustal structure derived from Pwave receiver function analysis by Mitra et al (2018) implies faulting beneath the Brahmaputra rather than along the topographic front. For blind thrust scenarios trenching may not provide much information on fault geometry, and therefore, high resolution seismic data may be highly useful in imaging the geometry of the faulted strata (Almeida et al, 2018).…”

Section: Future Directionsmentioning

confidence: 99%

Paleoseismological Studies in India (2016-2020): Status and Prospects

Rajendran¹,

Singh²,

Mukul³

et al. 2020

PINSA

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The last few years have witnessed consistent growth in paleoseismic investigations and active fault research in India. An overview of relevant publications during 2016-2020 indicates that this field is now widely accepted as a tool to characterize the seismic hazard in the country. Such studies initiated in the country in early nineties have gained momentum and widened its scope into a variety of tectonic and morphological settings.While earthquake frequency and fault activations are major objectives of such studies, the Indian researchers are now equally interested in constraining the fault geometry and the nature of near-surface crustal deformation, thereby contributing to earthquake hazard evaluations. This has been driven by an ever-increasing interaction between experts from associated fields like geomorphology, neotectonics, seismology, geodesy, modeling etc. Future challenges would include integrating the paleoseismological observations with the relevant geophysical inputs to develop physical models of the earthquake cycles, ultimately leading to an inventory of the active faults. Although there are gaps and disagreements on how things operated at different spatial and temporal scales, there have been broad agreements in general. The future should focus on evolving new strategies and methodologies to integrate different datasets in a coherent manner to yield practically relevant results and models that can explain data from various spatial and temporal scales.

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Seismic imaging of the Main Frontal Thrust in Nepal reveals a shallow décollement and blind thrusting

Cited by 28 publications

References 32 publications

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Himalayan earthquakes: a review of historical seismicity and early 21st century slip potential

Impact of topography on earthquake static slip estimates

Paleoseismological Studies in India (2016-2020): Status and Prospects

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