Lithospheric mantle dynamics in Central and East Java Region, Indonesia from local shear wave splitting measurements

IF 2.1 3区地球科学 Q2 GEOCHEMISTRY & GEOPHYSICS

Journal of Geodynamics Pub Date : 2023-09-20 DOI:10.1016/j.jog.2023.101998

Faiz Muttaqy , Syuhada Syuhada , Andri Dian Nugraha , James Mori , Nanang Tyasbudi Puspito , Pepen Supendi , Supriyanto Rohadi

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Abstract

We have investigated the local shear wave splitting of 30–300 km depth earthquakes from 38 BMKG stations between 2009 and 2020 to determine upper mantle dynamics beneath the Central and East Java (CEJ) region, Indonesia. A total of 2338 measurements is obtained and divided the analysis into two focal depths, i.e., shallow (≤ 100 km) and deep (100 – 300 km) events. (1) Both individual station measurements and spatially averaged data using shallow events (≤ 100 km) show the trench-perpendicular fast direction in the northern CEJ region. Thus, anisotropy in this domain may be associated with the downdip subduction-induced 2-D corner flow in the mantle wedge allowing A-type olivine fabric to develop. Meanwhile, the trench-parallel fast directions in the southern CEJ region may reflect some possible causes of anisotropy: the presence of a serpentinized mantle wedge that promotes the development of B-type olivine fabric and anisotropy through alignment of the melt pockets. We also suggest a change in the hydration state of the subducting slab can cause the predominant trench-perpendicular fast directions in the eastern CEJ region. (2) For deep events (100 – 300 km), fast directions are relatively trench-parallel in the eastern CEJ region and trench-perpendicular in the western CEJ region, suggesting the presence of fossilized anisotropy and 2-D mantle flow-induced anisotropy, respectively.

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印尼中爪哇和东爪哇地区岩石圈地幔动力学的局部剪切波分裂测量

我们研究了2009年至2020年间来自38个BMKG台站的30–300公里深度地震的局部剪切波分裂，以确定印度尼西亚中爪哇和东爪哇（CEJ）地区下方的上地幔动力学。共获得2338次测量，并将分析分为两个震源深度，即浅层（≤100 km）和深层（100-300 km）事件。（1）使用浅层事件（≤100km）的单站测量和空间平均数据都显示了CEJ北部地区的沟槽垂直快速方向。因此，该区域的各向异性可能与地幔楔中下倾俯冲引起的二维角流有关，从而使A型橄榄石组构得以发育。同时，南部CEJ区域的沟槽平行快速方向可能反映了各向异性的一些可能原因：蛇纹化地幔楔的存在促进了B型橄榄石组构的发展，并通过熔穴的排列促进了各向异性。我们还认为，俯冲板水化状态的变化可能导致东部CEJ地区的主要沟槽垂直快速方向。（2）对于深部事件（100–300 km），快速方向在东部CEJ区域相对平行于沟槽，在西部CEJ区域垂直于沟槽，分别表明存在石化各向异性和二维地幔流诱导的各向异性。

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来源期刊

Journal of Geodynamics 地学-地球化学与地球物理

CiteScore

4.60

自引率

0.00%

发文量

审稿时长

6-12 weeks

期刊介绍： The Journal of Geodynamics is an international and interdisciplinary forum for the publication of results and discussions of solid earth research in geodetic, geophysical, geological and geochemical geodynamics, with special emphasis on the large scale processes involved.