Seismic imaging of the double seismic zone in the subducting slab in Northern Chile

作     者：Pan Lu Haijiang Zhang Lei Gao Diana Comte Pan Lu;Haijiang Zhang;Lei Gao;Diana Comte

作者机构：Laboratory of Seismology and Physics of Earth's InteriorSchool of Earth and Space SciencesUniversity of Science and Technology of ChinaHefeiAnhui230026China Departamento de GeofísicaAdvanced Mining Technology CenterFacultad de Ciencias Físicas y Matem
aticasUniversidad de ChileBlanco Encalada2002SantiagoChile 

出 版 物：《Earthquake Research Advances》 (地震研究进展（英文）)

年 卷 期：2021年第1卷第1期

页      面：25-33页

核心收录：

学科分类：070801[理学-固体地球物理学] 07[理学] 0708[理学-地球物理学] 

基　　金：We are grateful for two anonymous reviewers for their constructive comments.This research is supported by National Natural Science Foundation of China under grant(41861134009) the PIA ANID grant(AFB180004) the ANID grant(PCI PII-180003) 

主　　题：Chile subduction Zone Double difference seismic tomography Double seismic zone Dehydration embrittlement 

摘      要：Double seismic zones are commonly observed in the subducting slabs in a global scale,serving as ideal examples for studying the seismogenetic mechanism of the intermediate-depth *** this study,we relocate earthquakes and determine seismic velocity models using the double-difference seismic tomography method in the northern Chile subduction zone where a double seismic zone *** results suggest that the double seismic zone in northern Chile is located at about 50-140 km depth,with an interval of approximately 20 km between the two *** upper seismic zone is characterized by relatively low Vp(~7.8-8.0 km/s),low Vs(~4.4-4.5 km/s)and high Vp/Vs(~1.85)above the depth of~90 km,while the region below~90 km is distinguished by relatively high Vp(~8.2 km/s),high Vs(~4.8 km/s)and slightly high Vp/Vs(~1.75),which may be related to a series of dehydration reactions of hydrous minerals in the subducted oceanic *** comparison,the lower seismic zone is featured by the anomaly of low Vp/Vs(~1.7),although some local areas may consist of relatively high Vp/Vs values(~1.8),possibly due to the dehydration reaction of *** on the Vp,Vs,Vp/Vs anomalies combined with previous petrological experiments and thermodynamic models,it can be derived that intermediate-depth earthquakes are mainly related to the dehydration of various hydrous minerals in the subducting *** dehydration process of hydrous minerals releases water into the subducting slab and subsequently leads to the increase of pore fluid pressure and the decrease of effective normal stress,thus causing the occurrence of brittle failure and intermediate-depth earthquakes in subduction *** imaging results of the northern Chile subduction zone further indicate that the existence of the double seismic zone is related to the dehydration process of different hydrous minerals.