宽频地震计及倾斜、重力仪对长周期波动信号的综合观测
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摘要
报道了在武汉华中科技大学地震与固体潮试验站的同一观测平台上,用数字宽频地震计、倾斜仪及重力仪对长周期地震波动信号的综合观测结果,以及各观测的对比和分析.近3年来.不同的观测仪器同时观测到了几十个形态一致、信号较弱而且成分复杂、持续时间大多约为2—3天的异常波(震颤).分析表明,这些异常震颤中的一部分由来自西太平洋进入中国大陆及近海的台风产生,其信号强弱主要与台风运动中心进入中国大陆近海后与观测点之间的距离,以及风速大小这两个因素密切关联.另外,还有一部分异常震颤信号的产生原因不明.频谱分析结果显示,与平常的背景噪声信号相比,异常震颤信号的成分较为丰富,除了3—5 min周期的信号外,还含有20-30 min,甚至一小时以上的长周期信号.我们以多种观测仪、长时间的连续观测结果表明,这种震颤信号是真实的和普遍存在的.其产生原因和机制还有待更广泛和深入的研究.
This paper reports the result of a joint observation of long period seis- mic signals with broadband digital seismometer,tiltmeter and gravimeter at the HUST station,Wuhan of China.The observed data were compared and ana- lyzed.Since 2005,these different instruments have synchronously recorded sev- eral tens of pattern alike,weak abnormal tremor signals,which lasted for two or three days.The signals involve complex components.Our analyzed result in- dicates that one part of the tremor signals is caused by the typhoon moving to the offshore region of China mainland from western Pacific Ocean.Amplitude of such signal is closely related to the distance between the center of typhoon and the observation station,and to the wide velocity of typhoon.Except for this, we do not know the cause of another kind of abnormal tremor.A spectral analy- sis shows that the abnormal tremor has the signal components of 3-5 min peri- od,20-30 min period,and even more than 1 hour period.With these spectrum components we may distinguish the tremor from background noise.The contin- uous records for a long time confirm the widespread existence of the tremor. But its mechanism needs to be further investigated.
This paper reports the result of a joint observation of long period seis- mic signals with broadband digital seismometer,tiltmeter and gravimeter at the HUST station,Wuhan of China.The observed data were compared and ana- lyzed.Since 2005,these different instruments have synchronously recorded sev- eral tens of pattern alike,weak abnormal tremor signals,which lasted for two or three days.The signals involve complex components.Our analyzed result in- dicates that one part of the tremor signals is caused by the typhoon moving to the offshore region of China mainland from western Pacific Ocean.Amplitude of such signal is closely related to the distance between the center of typhoon and the observation station,and to the wide velocity of typhoon.Except for this, we do not know the cause of another kind of abnormal tremor.A spectral analy- sis shows that the abnormal tremor has the signal components of 3-5 min peri- od,20-30 min period,and even more than 1 hour period.With these spectrum components we may distinguish the tremor from background noise.The contin- uous records for a long time confirm the widespread existence of the tremor. But its mechanism needs to be further investigated.
引文
①文中有关台风的资料与数据均来自中国气象局台风研究所的公开信息．http：//www．typhoon．gov．cn
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Kizawa T.1972.The recorders of the gravitational instruments before and after large earthquake[J].Overseas Earth- quakes,(1):39-41.
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Miyazawa M,Mori J.2005.Detection of triggered deep low-frequency events from the 2003 Tokachi-oki earthquake[J]. Geophys Res Lett,32(L10307):1-4.
Melbourne T I,Webb F H.2003.Slow but not quite silent[J].Science,300(5627):1886-1887.
Obara K.2002.Nonvolcanic deep tremor associated with subduction in southwest Japan[J].Science,296(5565): 1679-1681.
Rogers G,Dragert H.2003.Episodic tremor and slip on the Cascadia subduction zone:The chatter of silent slip[J].Sci- ence,300:1942-1943.
Rubinstein J L,Rocca M La,Vidale J E,Creager K C,Wech A G.2008.Tidal modulation of nonvolcnic tremor[J]. Science,319(5860):186-189.
Shelly D R,Beroza G C,Ide S,Nakamula S.2006.Low-frequency earthquakes in Shikoku,Japan,and their relationship to episodic tremor and slip[J].Nature,442:188-191.
Stokstad E.2002.Deep quakes slow but very steady[J].Science,295(5564):2 344-2 345.
Szeliga W,Melbourne T I,Miller M M,Santillan V M.2004.Southern Cascadia episodic slow earthquakes[J].Geophys Res Lett,31(L16602):1-4.
蔡亚先，吕永清，周云耀，程骏玲，邵中明，王惠群．1995．JCZ-1超宽频带地震计[J]．地壳形变与地震，15(3)：1-8．
蒋骏，苏红梅．张雁滨．2006．低频信号的精确采集与处理[J]．大地测量与地球动力学，26(3)：127-130．
唐林波，李世愚．苏昉．孙为，刘建新，和雪松．2002．地震前长周期事件的研究：历史与现状[J]．国际地震动态．(4)：1-6．
吴忠良．2001．地震学中的“暗物质”：“静地震”与地震预测研究的未来?[J]．国际地震动态，(9)：1-5．
许绍燮．2006．大尺度地层内的分层运动[J]．中国工程科学，8(6)：14-22．
杨又陵，赵根模，高国英，杨港生，韩润泉．2003．昆仑山口西8．1级地震新疆台网观测到的慢地震[J]．国际地震动态．(9)：1-4．
张雁滨，蒋骏，钱家栋，陈京，和升棋，张燕．和平．2002．地壳介质微变形与强震短临前兆[J]．地震学报．24(1)：103-108．
张雁滨，蒋骏．蔡亚先．吕永清，邵中明．2006．武汉台JCZ-1地震计LP通道的信号分析[J]．大地测量与地球动力学．26(4)：112-115．
赵根模，杨港生，陈化然．2001．寂静的前震与地震预测[J]．地震，21(1)：69—77．
Hirn A,Laigle M.2004.Silent heralds of megathrust earthquakes?[J].Science,305(5692):1917-1918.
Ito Y,Obara K,Shiomi K,Sekine S,Hirose H.2007.Slow earthquakes coincident with episodic tremors and slow slip events[J].Science,315(5811):503-506.
Kizawa T.1972.The recorders of the gravitational instruments before and after large earthquake[J].Overseas Earth- quakes,(1):39-41.
Miller M M,Melbourne T,Johnson D J,Summer W Q.2002.Periodic slow earthquakes from the Cascadia subduction zone[J].Science,295(5 564):2 423.
Miyazawa M,Mori J.2005.Detection of triggered deep low-frequency events from the 2003 Tokachi-oki earthquake[J]. Geophys Res Lett,32(L10307):1-4.
Melbourne T I,Webb F H.2003.Slow but not quite silent[J].Science,300(5627):1886-1887.
Obara K.2002.Nonvolcanic deep tremor associated with subduction in southwest Japan[J].Science,296(5565): 1679-1681.
Rogers G,Dragert H.2003.Episodic tremor and slip on the Cascadia subduction zone:The chatter of silent slip[J].Sci- ence,300:1942-1943.
Rubinstein J L,Rocca M La,Vidale J E,Creager K C,Wech A G.2008.Tidal modulation of nonvolcnic tremor[J]. Science,319(5860):186-189.
Shelly D R,Beroza G C,Ide S,Nakamula S.2006.Low-frequency earthquakes in Shikoku,Japan,and their relationship to episodic tremor and slip[J].Nature,442:188-191.
Stokstad E.2002.Deep quakes slow but very steady[J].Science,295(5564):2 344-2 345.
Szeliga W,Melbourne T I,Miller M M,Santillan V M.2004.Southern Cascadia episodic slow earthquakes[J].Geophys Res Lett,31(L16602):1-4.
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