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| Titel |
Describing earthquakes potential through mountain building processes: an example within Nepal Himalaya |
| VerfasserIn |
Zhen Zhang, Huai Zhang, Yaolin Shi, Baptiste Mary, Liangshu Wang |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250123528
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| Publikation (Nr.) |
 EGU/EGU2016-2801.pdf |
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| Zusammenfassung |
| How to reconcile earthquake activities, for instance, the distributions of large-great event
rupture areas and the partitioning of seismic-aseismic slips on the subduction interface, into
geological mountain building period is critical in seismotectonics. In this paper, we try to
scope this issue within a typical and special continental collisional mountain wedge within
Himalayas across the 2015 Mw7.8 Nepal Himalaya earth- quake area. Based on the Critical
Coulomb Wedge (CCW) theory, we show the possible predictions of large-great
earthquake rupture locations by retrieving refined evolutionary sequences with clear
boundary of coulomb wedge and creeping path inferred from interseismic deformation
pattern along the megathrust-Main Himalaya Thrust (MHT). Due to the well-known
thrusting architecture with constraints on the distribution of main exhumation zone
and of the key evolutionary nodes, reasonable and refined (with 500 yr interval)
thrusting sequences are retrieved by applying sequential limit analysis (SLA). We also
use an illustration method-‘G’ gram to localize the relative positions of each fault
within the tectonic wedge. Our model results show that at the early stage, during the
initial wedge accumulation period, because of the small size of mountain wedge,
there’s no large earthquakes happens in this period. Whereas, in the following stage,
the wedge is growing outward with occasionally out-of-sequence thrusting, four
thrusting clusters (thrusting ‘families’) are clarified on the basis of the spatio-temporal
distributions in the mountain wedge. Thrust family 4, located in the hinterland
of the mountain wedge, absorbed the least amount of the total convergence, with
no large earthquakes occurrence in this stage, contributing to the emplacement of
the Greater Himalayan Complex. The slips absorbed by the remnant three thrust
families result in large-great earthquakes rupturing in the Sub-Himalaya, Lesser
Himalaya, and the front of Higher Himalaya. The portion rupturing in Sub-Himalaya is
mainly great Himalaya earthquakes (M>8), with enough energy to rupture the
whole MHT, while the thrusting family 2 and 3 will cause mainly large earthquakes.
The averaged lifespan of single segment (inclined short lines) is growing from
the deformation front to the hinterland, while the occurrence frequency is just in
the opposite way. Thrusting slips in family 1-3 will enhance the coulomb wedge
development resulting in mountain building. Note that, all the large earthquake behaviors
described in this paper is a statistical characteristic, just the tendency distribution on
the MHT in one interval. Although our research domain is a section of the Nepal
Himalaya, the treatment proposed in this paper has universality in continental collisional
orogenic belt which having the same interseismic pattern. We also summary the
differences of seismogenic zones in oceanic subduction zone (Cascadia subduction
zone) and arc-continental subduction zone (Taiwan area). The different types of
interseismic pattern(mechanical patterns) are the controlling factors controlling
seismic potential on megathrust and thus impacting the mountain building history. |
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