中国南海西北次海盆海底地震记录的短时事件分析

Short duration events on OBS recordings in the Northwest Sub-basin of the South China Sea

本文对2019年10月—2020年5月在中国南海西北次海盆布放的宽频带海底地震仪的数据进行了分析,利用长短时窗均值比算法在单个海底地震仪台站拾取了多达25万个短时事件(SDE)。对拾取到的SDE信号特征进行了分析,并根据信号特征将事件分为连续短时事件(CSDE)和随机短时事件(R-SDE)。探讨C-SDE和R-SDE的信号源,可能的产生机制,结果表明:在布放时间段内中国南海西北次海盆存在着活跃的C-SDE信号源可能来自人类活动,如气枪放炮或者低频水声通信;R-SDE则来源于离台站很近的源,很可能是海底沉积层中的气体逃逸过程造成的沉积层破裂所导致,表明中国南海西北次海盆海底沉积层中存在气体泄露。

Based on the analysis of the data on broadband ocean bottom seismographs deployed in the Northwestern sub-basin of the South China Sea from October 2019 to May 2020.We detected more than 150000 short duration events(SDEs)at each OBS station by using STA/LTA algorithm.The characteristic of SDE signals is analyzed.According to different signal characteristics,these SDEs are classified as consecutive short duration events(C-SDEs)and random short duration events(R-SDEs).The possible generation mechanisms for C-SDEs and R-SDEs are analyzed,respectively.We infer there are active sources of C-SDE signal in the Northwest Sub-basin of the SCS.The source may be caused by human activities,such as air gun firing or low frequency hydroacoustic communication signals.The R-SDE sources appear close to the OBS stations,likely generated by the ruptures due to gas escape from seafloor sediments.RSDEs on OBS recordings indicate persistent gas escape from the sedimentary layer in the northwestern sub-basin of the SCS.