中国地震局王嘉沛与合作者，在最新研究中报道了泸定M_S6.8地震前重力场动态变化及其地壳物质迁移特征。相关论文于2024年10月22日发表于国际顶尖学术期刊《大地测量与地球动力学》杂志上。

2022年9月5日，四川省泸定县发生6.8级地震。本次地震发生在青藏高原东缘东南-顺时针物质挤压的关键部位，即鲜水河、龙门山和安宁河断裂带的Y型汇合处。

本研究利用2019-2022年地震前典型重力变化资料和生长体重力反演，获得了震区地壳密度的三维动态变化。结果表明，地震前泸定地区重力变化呈明显的四象限和梯度带分布。三维密度水平切片显示，2019.9-2020.9和2019.9-2021.9期间，震中在地壳中上部发生了小的密度变化。同时，周边区域呈现出正、负象限分布。这些观测结果表明，该地区可能处于稳定的锁定状态，锁定剪切力的方向为北西和北东。

2021.9-2022.8期间，震源区密度呈现出负密度变化，表明震源区处于扩张阶段，接近近震状态。三维密度垂向切片显示，在震中附近和鲜水河断裂带西侧，正、负密度向东南向迁移，表明物质向东南方向流出。沿龙门山断裂带观测到的震中局部负密度变化，可能与地震震源机制显示的北东向张应力有关。上述结果可为解释震前重力和密度变化提供依据，从而促进地震前兆理论的发展。

附：英文原文

Title: Dynamic changes of gravity field before the Luding M_S6.8 earthquake and its crustal material migration characteristics

Author: Qingqing Tan, Jiapei Wang

Issue&Volume: 2024/10/22

Abstract: On September 5, 2022, an earthquake of magnitude M_S6.8 occurred in Luding County, Sichuan Province. This earthquake occurred at the key part of the southeast-clockwise extrusion of material on the eastern margin of the Qinghai–Xizang Plateau, the Y-shaped confluence of the Xianshuihe, Longmenshan and Anninghe fault zones. In this study, the three-dimensional dynamic crustal density changes in the earthquake area are obtained by the typical gravity change data from 2019 to 2022 before the earthquake and gravity inversion by growing bodies. The results indicate that gravity changes presented an obvious four-quadrant and gradient belt distribution in the Luding area before the earthquake. The three-dimensional density horizontal slices show that small density changes occurred at the epicenter in the mid-to-upper crust between 2019.9 - 2020.9 and 2019.9–2021.9. At the same time, the surrounding areas exhibited a positive and negative quadrant distribution. These observations indicate that the source region was likely in a stable locked state, with locking-in shear forces oriented in the NW and NE directions. From 2021.9 to 2022.8, the epicentral region showed negative density changes, indicating that the source region was in the expansion stage, approaching a near-seismic state. The three-dimensional density vertical slices reveal a southeastward migration of positive and negative densities near the epicenter and on the western of the Xianshuihe Fault Zone, indicating that the material is flowing out to the southeast. The observed local negative density changes at the epicenter along the Longmenshan Fault Zone are likely associated with the NE-oriented extensional stress shown by the seismic source mechanism. The above results can provide a basis for interpreting pre-earthquake gravity and density changes, thereby contributing to the advancement of earthquake precursor theory.

DOI: 10.1016/j.geog.2024.09.006

Source: https://www.sciencedirect.com/science/article/pii/S1674984724001162