利用互相關方法探討大地電場與地震波的耦合行為

近幾年來，由於高品質連續地震資料的增加與電腦計算能力的提升，利用互相關方法從背景噪聲中提取測站間的格林函數在地震學中已被廣泛的使用。本研究即應用此互相關方法分析臺灣大地電場的連續資料，進而從自然電位中提取與地震波傳遞相關的訊號，藉以探討地震波與電場訊號的耦合情形。本研究使用的測站為本團隊在臺灣島內建置的20個大地電場觀測站，取用的資料為水平方向之即時連續訊號，採樣率為15 Hz，時間段的選取從2013年3月到2014年2月，總共一年的資料長度。在前人的研究中從理論推導上已證明電場訊號的傳遞會伴隨著地震波移動，此現象稱為震電響應，而這類同震波傳播的震電現象，卻從未在大尺度的實際觀測資料中被驗證，本研究則為首次實際觀測到此一現象。在此次研究中顯示：利用互相關方法分析自然電位的資料能夠得到近似P波速度傳播的電場異常。以埔里站為虛擬源（近台灣島的中心點），透過震波的速度分析探討中部臺灣下方反射層的震電訊號，顯示高度震電相關的能量大約出現在深度10到60公里，與前人研究中描述關於臺灣山區下方低電阻帶的範圍大致相同，此發現與前人的理論研究中易發生震電耦合的地質環境十分符合。

關鍵字

震電響應；互相關方法

並列摘要

Recently, using cross-correlation method to extract Green function between seismic stations from ambient noises has been widely used in seismology owing to the rapid growth of seismic data set and the significant improvement of the computing power. In this study, we apply this method to retrieve seismic related signals from the continuous data of the geoelectric field in Taiwan. Geoelectric signals used are from twenty real-time horizontal self-potential stations with 15 Hz sampling rate during March 2013 to February 2014. According to previous studies, it has been theoretically proved that electric signals can be accompanied with the movement of seismic waves, which is known as “seismoelectric response”. However, those co-seismic wave signals are observed in real data from this study for the first time. As a result, we found that the geoelectric field anomalies are highly related to the P wave propagation and those anomalies are sensitive to the geological structures with the fluid presented, which is also stated by the theoretical calculations from previous studies.

並列關鍵字

seismoelectric response ； cross-correlation method

參考文獻

Bertrand, Edward., Martyn Unsworth, Chih-Wen Chiang, Chow-Son Chen, Chien-Chih Chen, Francis Wu, Ers¸an Türkog˘ lu, Han-Lun Hsu and Graham Hill, Magnetotelluric evidence for thick-skinned tectonics in central Taiwan, Geology, V. 37; no. 8; p. 711–714, 2009

Nyquist, Jonathan E. and Charles E. Corry, Self-potential: The ugly duckling of

Bensen, G. D., M. H. Ritzwoller, M. P. Barmin, A. L. Levshin, F. Lin, M. P. Moschetti, N. M. Shapiro and Y. Yang, Processing seismic ambient noise data to obtain reliable broad-band surface wave dispersion measurements, Geophys. J. Int. 169, 1239–1260, 2007

Bertrand, Edward., Martyn J. Unsworth, Chih-Wen Chiang, Chow-Son Chen, Chien-Chih Chen, Francis T. Wu, Ersan Türkoğlu, Han-Lun Hsu and Graham J. Hill, Magnetotelluric imaging beneath the Taiwan orogen: An arc-continent collision, Journal of Geophysical Research, VOL. 117, B01402, 2012

Block, Gareth I. and John G. Harris, Conductivity dependence of seismoelectric wave phenomena in fluid-saturated sediments, Journal of Geophysical Research, VOL. 111, B01304,2006

國際替代計量

利用互相關方法探討大地電場與地震波的耦合行為

未授權

主題瀏覽