卡奇大陆断层(印度西部)的分段地质电学特征及其对地震危害的意义

IF 2.7 3区 地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS Tectonophysics Pub Date : 2024-07-14 DOI:10.1016/j.tecto.2024.230422
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引用次数: 0

摘要

确定震源特征对于评估地震灾害至关重要,尤其是像卡奇地区长达 150 公里的卡奇大陆断层(KMF)这样的活动断层。KMF 被不同方向(西北-东南到东北-西南)的横向断层横向移位。为了更好地了解 KMF,我们对该断层各段的五个南北走向磁能图勒(MT)剖面(两个最近获得的剖面和三个之前公布的剖面)进行了联合解释。这些剖面覆盖了断层的不同段落,长度从 15 公里到 81 公里不等。根据二维 MT 数据反演得出的地电剖面分析表明,KMF 在横断层附近向南倾斜,而在远离横断层的地方则陡然向北倾斜。孔明盆地的中部和东部地区地震活动频繁。因此,在进行地震灾害评估时,我们考虑在高明区的所有四个地段发生一次北倾的 Mw 7.6 级地震。为了考虑不确定性,我们进行了参数测试,探索了一系列应力下降值、Kappa 值和质量因子 (Q),这些都是由卡奇地区的多项研究提出的。据估计,所有四个地段的最大峰值地面加速度(PGA)为 0.85 g(软岩条件下,Vs 为 500 m/s)。研究显示,与基于向南倾斜的 KMF 的估计值相比,KMF 以南的地点(如布吉和巴查乌)的 PGA 下降了 14-38%,而 KMF 以北的地点(如拉帕尔和卡夫达)的 PGA 上升了 30-47%。这强调了考虑和估计断层倾角沿其长度变化的重要性,以及这种变化如何影响构造板块内部的地震危险评估。
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Segmented geoelectrical characterization of the Kachchh Mainland Fault (Western India) and significance for seismic Hazard

Characterizing seismic sources is crucial for assessing seismic hazards, particularly for active faults like the Kachchh Mainland Fault (KMF), a 150 km long fault in the Kachchh region. The KMF is laterally displaced by transverse faults with different orientations (NW-SE to NE-SW). To better understand the KMF, a joint interpretation of the five North-South trending Magnetotelluric (MT) profiles (two recently acquired profiles and three earlier published ones) is conducted across various segments of the fault. These profiles covered diverse stretches across the fault, ranging from 15 to 81 km in length. Analysis of the geoelectric sections derived from 2-D MT data inversion revealed that the KMF dips to the south in the vicinity of the transverse faults while it takes on a steep north-dipping orientation farther away from the transverse faults. The central and eastern parts of the KMF are seismically active. Therefore, seismic hazard assessments is carried out by considering a magnitude Mw 7.6 scenario earthquake with a northward dip for all four segments of the KMF. To account for uncertainty, parametric testing was conducted, exploring a range of stress drop values, Kappa values, and quality factors (Q) as proposed by various studies in the Kachchh region. The maximum peak ground acceleration (PGA), of 0.85 g (under soft rock conditions with Vs of 500 m/s), is estimated due to the considered scenario earthquake along all four segments. The study revealed that the PGA decreased by 14–38% at sites south of the KMF (such as Bhuj and Bhachau) and increased by 30–47% at sites located north of the KMF (like Rapar and Khavda) compared to estimates based on a southward dipping KMF. This underlines the significance of considering and estimating variations in fault dip along its length and how such variations can impact seismic hazard assessments within tectonic plate interiors.

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来源期刊
Tectonophysics
Tectonophysics 地学-地球化学与地球物理
CiteScore
4.90
自引率
6.90%
发文量
300
审稿时长
6 months
期刊介绍: The prime focus of Tectonophysics will be high-impact original research and reviews in the fields of kinematics, structure, composition, and dynamics of the solid arth at all scales. Tectonophysics particularly encourages submission of papers based on the integration of a multitude of geophysical, geological, geochemical, geodynamic, and geotectonic methods
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