Hussain Hamid, Shuangxi Zhang, Usman Muhammad, Abid Muhammad
Department of Geophysics, School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China.
Key Laboratory of Geospace Environment and Geodesy of Ministry of Education, Wuhan University, Wuhan 430079, China.
Entropy (Basel). 2020 Sep 11;22(9):1016. doi: 10.3390/e22091016.
The Tibetan Plateau is considered to be one of the best natural laboratories for seismological research. This study sought to determine the spatial variations of -values in the western part of the Tibetan Plateau, along with its surrounding areas, and the relation with the region's fault blocks. The study region lies within 27-36.5° N, 78-89° E, and its fracture structure consists of strike-slip faults, as well as normal and thrust faults. A catalog record from 2009-2019 provided 4431 well-centered earthquakes that varied in magnitude from 0.1 to 8.2 M. The record was obtained from China's seismological network, which is capable of recording low magnitudes to analyze -values in the study area. The key findings of this study are as follows: (1) the range of earthquake depth in the region was 0-256 km, with the depth histogram showing a high frequency occurrence of shallow earthquakes in the area; (2) a time histogram showed that the major earthquakes occurred between 2014-2015, including the notable 2015 Gorkha earthquake (M = 8.2); (3) the -value computed in the study area was 0.5 to 1.6, but in most of the study area, the -value ranged from 0.6 to 0.9, which was a low to intermediate value, due to the presence of strike-slip faults in the central part of the study area and underthrusting in the region (south of the study area); and (4) a high -value was found in the northwestern and eastern regions of the area, which proved that the area is prone to small earthquakes in the near future. The study also showed that the central and southern areas of the study region had low to intermediate -values, meaning that it is prone to destructive and massive earthquakes with high magnitudes, such as the Gorkha earthquake (southern part of the study area). Low -values revealed the degree of variation in rock properties, including large stress and strain, a fractured medium, a high deformation rate, and large faults. Small -values were observed when the stress level was high in the investigated region, which might be used to predict a massive high-magnitude earthquake in the near future.
青藏高原被认为是地震学研究的最佳天然实验室之一。本研究旨在确定青藏高原西部及其周边地区的 值空间变化，以及与该地区断层块的关系。研究区域位于北纬27 - 36.5°，东经78 - 89°，其断裂构造由走滑断层以及正断层和逆冲断层组成。2009 - 2019年的目录记录提供了4431次震中定位良好的地震，震级从0.1到8.2 M不等。该记录来自中国地震台网，该台网能够记录低震级地震以分析研究区域的 值。本研究的主要发现如下：(1) 该区域地震深度范围为0 - 256 km，深度直方图显示该区域浅源地震发生率较高；(2) 时间直方图显示，主要地震发生在2014 - 2015年之间，包括著名的2015年戈尔卡地震（震级M = 8.2）；(3) 研究区域计算出的 值为0.5至1.6，但在研究区域的大部分地区， 值范围为0.6至0.9，这是一个低到中等的值，这是由于研究区域中部存在走滑断层以及该区域（研究区域南部）的俯冲作用；(4) 在该区域的西北部和东部地区发现了高 值，这证明该区域在不久的将来容易发生小地震。研究还表明，研究区域的中部和南部地区 值为低到中等，这意味着它容易发生具有高震级的破坏性大地震，如戈尔卡地震（研究区域南部）。低值揭示了岩石性质的变化程度，包括大应力和应变、破碎介质、高变形率和大断层。当研究区域应力水平较高时观察到小 值，这可能用于预测不久的将来发生的大规模高震级地震。
