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Principal component analysis of geomagnetic data associated with Panzhihua Ms 6.1 earthquake - the preparatory result. Li Junhui 1 、 3 Li Qi 2 Yang Dongmei 2 1 Seismological Bureau of Anhui, Hefei, China. 2 Institutes of Geophysics, CEA, Beijing
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Principal component analysis of geomagnetic data associated with Panzhihua Ms 6.1 earthquake- the preparatory result Li Junhui1、3 Li Qi2 Yang Dongmei2 1 Seismological Bureau of Anhui, Hefei, China. 2 Institutes of Geophysics, CEA, Beijing 3、National Geophysical Observatory at Mengcheng,Hefei 230031 e-mail:lijunhui@mail.ustc.edu.cn
Table of contents • Ms 6.1 Pan Zhihua earthquake and observations site. • PCA method • PCA result of this earthquake • Discussion and conclusion
一、 about this earthquake Wenchuan earthquake sequence Ms 6.1 About 600Km far from Ms 8.0
Stations and Earthquake • 西昌台阵9个磁通门仪器。 • 8月30日16点发生Ms6.1级地震。 • 距最近的台站平地仅6.4Km、南山40Km、会理60Km. • 仪器:GM4
ULF geomagnetic data Components Geomagnetic 3 component (H, D[declination], Z[vertical]) Observatory Nanshan HUILi Pingdi Sampling 1Hz Analysisterm Jan 1 2008– Dec 31 2008 Feb march April No data Technical parameter of GM4
二、procedure of PCA • Data: second; • Stations: NSH、HLC、Pd; • 1800 point; • Y1=Dnsh(i); • Y2=Dhlc(i); • Y3=Dpd(i); • Y=[Y1,Y2,Y3];
procedure of PCA • 1Hz sample per 30 min 3 stations yNS(1:1800) ,yPD(1:1800),yHL(1:1800). • Y=[yNST, yPDT yHLT]; Transpose matrix • variance matrix R=YYT ; • Calculate the eigenvalue of R 入1,入2,入3 (入1>入2>入3 ). 3 temproal eigenvalue sequence
Signals observed on the ground-based magnetometer Katsumi Hattori 2004
The variation of first principal component with that of Ap index in April, 2008.
analysis of the third principal component • 选取台站周围100Km范围内地震。 • 计算地震释放能量 • 与第三主成分对比分析。
四 Discussion and conclusion • The first principal component is found to be the signal originated in the solar–terrestrial effects such as geomagnetic pulsation. • the second principal component, the local artificial noise is included. • the smallest third component in the local midnight at the Panzhuhua region, it indicated increase in the third eigenvalue about 40 days before the large earthquake. • These features are likely to be correlated with large earthquake.