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首页> 外文期刊>Pure and Applied Geophysics >Earthquakes in the Garhwal Himalaya of the Central Seismic Gap: A Study of Historical and Present Seismicity and Their Implications to the Seismotectonics
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Earthquakes in the Garhwal Himalaya of the Central Seismic Gap: A Study of Historical and Present Seismicity and Their Implications to the Seismotectonics

机译：中央地震差距Garhwal Himalaya的地震：对历史和呈现地震性的研究及其对地震术的影响

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摘要

The historical and the present seismicity catalogues of the Garhwal Himalaya have been studied for their spatio-temporal variations and their implications on the seismotectonics of the region. The Micro-Seismicity, Fractal dimensions (D-c) and Frequency Magnitude Distribution (b-value) coupled with the available literature on geology, geomorphology and geophysics have been used to derive the seismotectonics and stress level changes in the region. The seismic cross sections for the relocated micro-seismicity, focal mechanisms and the swath profiles (for the presence of Physiographic Transition 2 (PT2) at the foothill of the Higher Himalaya) indicate the constant presence of the Mid-Crustal Ramp (MCR) in the detachment plane and its active seismogenic nature. The comparison of this scenario suggests the constant presence of seismogenically active MCR structure throughout the Central Seismic Gap. The seismic cross sections further reveal that the sensu stricto Main Central Thrust (Munsiari Thrust) is also a site of generation of the micro-seismicity in few segments due to its reactivation by thrusting along the MCR. The high fractal dimension value (D-c = 1.47) suggests the heterogeneous nature of the region, owing to the presence of local faults and transverse tectonics. The high stress accumulation in the Garhwal Himalaya with low b value (b = 0.70) suggests the high probability of occurrence of a larger or greater earthquake in the near-future. Further, the study also reveals that the 2011 Chamoli earthquake of M 5.0, preceded by a quiescence period of nearly a year shows different stress levels before and after its occurrence, which is well constrained with the increased moderate earthquake activity around the Chamoli region. This increased seismic activity and stress conditions in the Chamoli region suggest the high possibility of the occurrence of major earthquakes, hence the study recommend for a detailed seismic hazard evaluation of the region.
机译：研究了加尔瓦尔-喜马拉雅山的历史和当前地震活动目录的时空变化及其对该地区地震构造的影响。利用微震活动性、分维（D-c）和频率-震级分布（b值）以及地质学、地貌学和地球物理学的现有文献，得出了该地区的地震构造和应力水平变化。重新定位的微地震活动性、震源机制和swath剖面的地震横截面（在较高喜马拉雅山麓存在地形转换2（PT2））表明，滑脱面中持续存在中地壳斜坡（MCR）及其活跃的孕震性质。这种情况的比较表明，在整个中央地震带间隙中，持续存在地震活跃的MCR结构。地震横截面进一步显示，狭义主中央逆冲断层（Munsiari逆冲断层）也是在少数地段产生微地震活动的场所，这是由于其沿MCR逆冲重新激活。高分维值（D-c=1.47）表明，由于局部断层和横向构造的存在，该区域具有非均质性。低b值（b=0.70）的加尔瓦尔喜马拉雅山脉的高应力累积表明，在不久的将来发生更大或更大地震的可能性很高。此外，该研究还显示，2011年查莫利5.0级地震（之前有近一年的平静期）在其发生前后表现出不同的应力水平，这与查莫利地区周围中等地震活动的增加有很好的制约作用。查莫利地区地震活动和应力条件的增加表明，发生大地震的可能性很高，因此研究建议对该地区进行详细的地震危险性评估。

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