南海西北次海盆海底地震记录的短时事件分析

王宜志 杨挺 刘晨光 刘丹 吴越楚

王宜志,杨挺,刘晨光,刘丹,吴越楚. 2023. 南海西北次海盆海底地震记录的短时事件分析. 地震学报,45(0):1−14 doi: 10.11939/jass.20220175
引用本文: 王宜志,杨挺,刘晨光,刘丹,吴越楚. 2023. 南海西北次海盆海底地震记录的短时事件分析. 地震学报,45(0):1−14 doi: 10.11939/jass.20220175
Wang Y Z,Yang T,Liu C N A,Liu D,Wu Y C. 2023. Short Duration Events on OBS recordings in the Northwestern Sub-basin of the South China Sea. Acta Seismologica Sinica,45(0):1−14 doi: 10.11939/jass.20220175
Citation: Wang Y Z,Yang T,Liu C N A,Liu D,Wu Y C. 2023. Short Duration Events on OBS recordings in the Northwestern Sub-basin of the South China Sea. Acta Seismologica Sinica45(0):1−14 doi: 10.11939/jass.20220175

南海西北次海盆海底地震记录的短时事件分析

doi: 10.11939/jass.20220175
基金项目: 国家自然科学基金(92058209)和深圳市科创委项目(KQTD20170810111725321; JCYJ20180504170422082)共同资助
详细信息
    作者简介:

    王宜志,在读博士研究生,主要从事海底地震仪研制及其非地震信号研究,e-mail:wangyz@mail.sustech.edu.cn

    通讯作者:

    杨挺,博士,教授,主要从事海洋地球物理和地震学研究以及相关仪器研发工作,e-mail:tyang@sustech.edu.cn

  • 中图分类号: P315.6

Short Duration Events on OBS recordings in the Northwestern Sub-basin of the South China Sea

  • 摘要: 本文对2019年10月—2020年5月在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,利用长短时窗均值算法在单个OBS台站拾取了多达12万个短时事件。根据信号特征以及可能的成因机制,可将事件分为连续性短时事件(C-SDE)和随机短时事件(R-SDE)。C-SDE的主要特征是在一段时间内连续且有规律发生的短时事件;包含多个事件组,事件组间隔约100—300 s,每个事件组包括3—10个持续约1 s的单波;其主频介于20—44 Hz之间,不同台站信号主频的不同可能是因信号源到台站距离不同而衰减的结果;C-SDE能量较强,在间距约105 km的三个OBS台站的三个分量上均有记录。R-SDE的主要特征是随机发生,持续时间约0.3—2 s;主频集中于8—25 Hz,在频谱上常呈现双波峰;由于其事件能量较小,很难在多个台站上拾取到同一个事件。本文探讨了C-SDE和R-SDE的信号源可能的产生机制,推断该时间段内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所产生的破裂过程所导致,表明南海西北次海盆海底沉积层中存在气体泄露。

     

  • 图  1  典型SDE波形及幅度频谱

    (a—b)马尔马拉海2011年布放的OBS(OBS-01台站)记录的海底沉积层中气泡逃逸产生的SDE的三分量波形和幅度频谱( Tsang Hin Sun et al,2019); (c—d)东北太平洋布放的OBS台站记录的2012-11-03 19:00:00的鲸鱼叫声产生的SDE的三分量波形和幅度频谱(数据来源:IRIS ,网络号:X9 ,台站号:BS080) ( Kuna,Nábělek,2021)。

    Figure  1.  Waveforms and amplitude spectra of typical SDEs。

    (a,b) Three-component waveforms and amplitude spectra of SDEs from bubble escape in seafloor sediment recorded by OBS (OBS-01 station) in the Sea of Marmara (Tsang Hin Sun et al,2019); (c,d) Three-component waveforms and amplitude spectra of SDEs produced by whale calls on OBS stations (IRIS data. Network:X9,Station:BS080,Begin time:2012-11-03 21:16:52) in the Northeast Pacific.) (Kuna ,Nábělek,2021).

    图  2  海底地震仪在南海西北次海盆布放位置

    Figure  2.  Sites of OBSs in the northwest sub-basin of the SCS

    图  3  STA/LTA方法拾取SDE示意

    (a)单个SDE波形序列;(b)连续SDE波形序列;(c)单个SDE的STA/LTA的特征曲线;(d)连续SDE的STA/LTA的特征曲线 。粉色区域为噪音数据,浅绿色区域为SDE信号数据。

    Figure  3.  Example of SDEs detected by the STA/LTA method

    (a,b). The waveform of a single SDE and consecutive SDEs. The pink box is noise data and the light green box is the SDE signal data. (c,d). Character curves of a single SDE and the consecutive SDEs in detections using STA/LTA method.

    图  4  SDE数量随时间的变化

    (a) 2019年10月—2020年5月间,K02,K03,K08数量变化(日统计)的时序图; (b) 2020年5月3日—10日间,SDE在K02,K03,K08台站拾取的数量变化(小时统计)时序图; (c) 2020年1月3日—10日间,SDE在K02,K03,K08台站拾取的数量变化(小时统计)时序图

    Figure  4.  Temporal distribution of the SDE number

    (a). Temporal distribution of the SDE number in OBS stations (K02,K03,K08) from October 2019 to May 2020;(b). Temporal distribution of the SDE number in OBS stations (K02,K03,K08) from May 3 to 10, 2020;(c). Temporal distribution of the SDE number in OBS stations (K02,K03,K08) from January 3 to 10,2020.

    图  6  C-SDE波形图

    (a)相距约52 km的K02,K03,K08台站上垂直分量的C-SDE信号,R1,R2,R3,R4分别表示R-SDE, E1表示地震事件;(b) 相距约52 km的K02,K03,K08台站上垂直分量的单一GE波形;(c) K08台站上三个分量(E,N,Z)的波形

    Figure  6.  Waveform of C-SDEs

    (a) The vertical components of C-SDE signals on OBS stations (K02, K03, K08) about 52 km apart,R1,R2,R3,R4 are the R-SDEs,and E1 is an earthquake event.(b) The GEs waveforms of vertical components on OBS stations (K02,K03,K08).(b) The waveform of the three components (E,N,Z) on K08 station.

    图  5  SDE信号的频率分布

    Figure  5.  The frequency distribution of SDEs。

    图  7  K02(a), K03(b)和 K08(c)台站观测到的GE信号的波形及频谱图

    Figure  7.  The waveforms and spectra of GE signals on OBS stations (K02,K03,K08)

    图  8  K08台站地震信号(a)与典型R-SDE信号(b-f)波形及频谱图

    Figure  8.  The waveforms and spectra of earthquake signals (a) and typical R-SDE signals (b-f) on the K08 station

    图  9  不同时间尺度下各种机制导致的C-SDE的波形对比。(a,b)OBS台站上的鲸鱼叫声记录(数据来源:IRIS data。网络号:X9,台站号:BS080,时间:2012-11-03 19:00:00) (Kuna ,Nábělek, 2021)、(c,d)短周期OBS的人工震源(气枪)信号和(e,f)本文研究

    Figure  9.  Comparison of C-SDEs caused by various mechanisms on different time scales. (a,b) Whale songs recorded by OBS station (IRIS data records at OBS stations Network:X9, Station:BS080, Begin time:2012-11-03 19:00:00) (Kuna ,Nábělek, 2021),(c,d) Artificial sources (air guns) signal recorded by short-period OBS and this paper studied(e,f).

    表  1  宽频带海底地震仪实验信息

    Table  1.   Experimental information of broadband OBS

    台站编号经度/°E纬度/°N深度/m投放日期
    年-月-日
    回收日期
    年-月-日
    K08115.49917.799−3 780.012019-10-202020-05-15
    K03115.99917.799−3 835.82 2019-10-20 2020-05-15
    K02116.49917.799−3 896.382019-10-212020-05-14
    下载: 导出CSV

    表  2  STA/LTA方法拾取SDE参数设置表

    Table  2.   The parameter set of SDE pickup with the STA/LTA method

    参数名称STA 时间LTA 时间开始触发值结束触发值持续时间信噪比
    设置值0.1(s)50 (s)860.05—2 (s)3
    下载: 导出CSV

    表  3  SDE拾取结果

    Table  3.   The pick-up quantity of SDEs on each station

    StationHHEHHNHHZTotal
    K02280208572140010153751
    K034154912205118829182429
    K08776938394293849255484
    下载: 导出CSV

    表  4  2020年5月3—9日,C-SDE信号发生及持续时间

    Table  4.   Occurrence and duration of C-SDE signal from May 3 to 9,2020

    序号日期
    年-月-日
    开始时间
    时:分:秒
    结束时间
    时:分:秒
    持续时间
    时:分:秒
    12020年5月3日0:54:157:43:106:48:55
    22020年5月3日16:30:351:12:50(+1天)8:42:15
    32020年5月5日0:33:307:55:307:22:00
    42020年5月6日3:58:2513:50:259:52:00
    52020年5月8日3:28:408:24:104:55:30
    62020年5月9日1:30:128:38:557:08:43
    72020年5月9日18:42:0722:20:103:38:03
    下载: 导出CSV
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