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An estimation of probable seismic hazard in the active deformation front of the Himalayan arc
Journal of Earth System Science ( IF 1.3 ) Pub Date : 2021-02-17 , DOI: 10.1007/s12040-020-01544-4
Basab Mukhopadhyay

Research highlights

  • The earthquake catalogue of Himalaya between 1225 and 2017 is compiled.

  • The active tectonic front of the Himalaya is subdivided into 14 zones (1–14) between MFT and MCT.

  • The moment ratio < 1 in 10 zones [1 (Kashmir), 3 (Kangra), 5 (Almora), 6 (Central-gap1), 8 (Pokhra–Kathmandu), 9 (Everest), 11 (W Bhutan), 12 (E Bhutan), 13 (Arunachal) and 14 (Eastern Syntaxis)], show good agreement between geodetic and seismic moment rates, and are vulnerable for large earthquake (Mw 8.15–8.95) in distant future.

  • Presently, zones 2 (Kishtwar), 4 (Nahan), 7 (Central-Gap 2) and 10 (Sikkim) are vulnerable as they show moderate-low b-values, high moment-ratio (>1) and long seismic hiatus. Moreover, zones 2, 4, 10, 12 and 13 have un-ruptured patches of Main Himalayan Thrust (MHT) and have capacity to spawn Mw 6.75–7.95 earthquake any point of time.

  • The rupture generated in these zones will transgress the zone boundaries and terminate in the sub-surface Precambrian ridge systems continuing from Peninsular India below Himalaya.

Abstract

In this study, the strain rate (SR) in grid-nodes in and around Himalaya that was computed from 1252 GPS station data, is also used. The earthquake catalogue of Himalaya between 1225 and 2017 is compiled. The active tectonic front of the Himalaya is subdivided into 14 zones between MFT and MCT, where MHT is locked. For each zone, magnitude-completeness (Mc), ‘a’ and ‘b’ values, geodetic moment rate (Mgd), seismic moment rate (Msm), moment ratio (Mgd/Msm) are calculated. It is observed that the moment ratio is <1 in zone 1 (Kashmir), 3 (Kangra), 5 (Almora), 6 (Central-gap 1), 8 (Pokhra–Kathmandu), 9 (Everest), 11 (W Bhutan), 12 (E Bhutan), 13 (Arunachal) and 14 (Eastern Syntaxis). These zones show good agreement between geodetic and seismic moment rates, and are vulnerable to large earthquakes (Mw 8.15–8.95) in the distant future. Presently, zone 2 (Kishtwar), 4 (Nahan), 7 (Central-Gap 2), and 10 (Sikkim) are vulnerable as they show moderate-low b-values, high moment ratio (>1), and long seismic hiatus for large earthquakes. Moreover, zones 2, 4, 10, 12, and 13 have un-ruptured patches of MHT and have the capacity to spawn Mw 6.75–7.95 earthquake at any point of time. The rupture generated in these zones will transgress the zone boundaries and terminate in the sub-surface Precambrian ridge systems continuing from Peninsular India below Himalaya.



中文翻译:

喜马拉雅弧活动变形前的可能地震危险性估算

研究重点

  • 编制了喜马拉雅1225年至2017年的地震目录。

  • 喜马拉雅山的活跃构造锋被划分为MFT和MCT之间的14个区域(1-14)。

  • 力矩比<10个区域中的1 [1(克什米尔),3(坎格拉),5(阿尔莫拉),6(中央差距1),8(波赫拉–加德满都),9(珠穆朗玛峰),11(不丹),12 (不丹),13(阿鲁纳恰尔)和14(东部语法)]显示出大地和地震矩率之间的良好一致性,并且很容易在遥远的将来遭受大地震(M w 8.15–8.95)。

  • 目前,第2区(基什瓦尔),第4区(纳汉),第7区(中央缺口2)和第10区(锡金)很脆弱,因为它们显示出中等低的b值,高的矩比(> 1)和长的地震间隔。此外,第2、4、10、12和13区具有未破裂的喜马拉雅主冲断面(MHT),并具有在任何时间点产生6.75–7.95 M w地震的能力。

  • 在这些区域中产生的破裂将越过区域边界,并终止于从喜马拉雅山以下的印度半岛延续的地下前寒武纪山脊系统。

抽象的

在这项研究中,还使用了从1252 GPS站数据计算出的喜马拉雅山内及周围的网格节点的应变率(SR)。编制了喜马拉雅1225年至2017年的地震目录。喜马拉雅山的活跃构造锋被划分为MFT和MCT之间的14个区域,MHT被锁定。对于每个区域,幅度完整性(M c),“ a ”和“ b”值,大地矩速率(Mgd),地震矩速率(Msm),力矩比(Mgd / Msm)被计算。在区域1(克什米尔),3(Kangra),5(Almora),6(中央空隙1),8(Pokhra–加德满都),9(珠穆朗玛峰),11(W)中,观察到的力矩比<1不丹),12(不丹),13(阿鲁纳恰尔)和14(东部语法)。这些区域在大地动量和地震矩速率之间显示出良好的一致性,并且在不久的将来很容易受到大地震(M w 8.15–8.95)的影响。目前,第2区(基什瓦尔),第4区(纳汉),第7区(中央差距2)和第10区(锡金)很脆弱,因为它们显示出中等低的b值,高的矩比(> 1)和长的地震间隔大地震。此外,区域2、4、10、12和13具有未破裂的MHT斑,并具有产卵的能力中号W¯¯在任何时间点6.75-7.95地震。在这些区域中产生的破裂将越过区域边界,并终止于从喜马拉雅山以下的印度半岛延续的地下前寒武纪山脊系统。

更新日期:2021-02-17
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