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Earthquake time Signature in SST and SLHF through analysis of 20 major EQ events of West Pacific Zone

Author Affiliations

  • 1Department of Physics, Gauhati University, Guwahati, INDIA

Res. J. Recent Sci., Volume 4, Issue (9), Pages 68-92, September,2 (2015)

Abstract

The paper aims at identification of possible signatures of an impending earthquake (EQ) in parameters like surface latent eat flux (SLHF) and sea surface temperature (SST) by analysing 20 EQs with magnitude >6 occurring in the west pacific coastal and off coastal regions. For this purpose, SLHF magnitudes are taken from NCEP/ NCAR reanalysis data (1.8 0×1.80grid) and SST values are obtained from NOAA/ NCDC with grid size 0.250×0.250. The daily spatial SST and SLHF distribution obtained from NOAA is also examined over the epicenter zones of earthquake under consideration. The paper gives the detailed statistical approaches adopted for extracting EQ signatures in the two parameters considered here. The analysis starts with defining a parameter called Anomaly Index (AI) which is calculated by comparing the daily values of SST and SLHF over the epicenter area with the long term (10 yrs) average values of the parameters. While calculating the long term average values (x?), the data are exclusively screened for non-EQ days for periods two month prior to and one month after the occurrence of the event. The x? values are compared with corresponding EQ day data (x) and the resultant magnitudes of X=(x-x?) are then normalised for removing non- EQ time influences by defining the anomaly parameter as = ??(???')?, where (?) is the standard deviation of x' taking mean data value of each year. To identify EQ time anomaly, the mean (µ) and the standard deviation (s) is calculated from the fluctuations of AI values and only when the value crosses, µ+2s limit, the situation is marked as EQ time anomaly over the earthquake region. The paper finally presents that prediction reliability of an impending earthquake through SST and SLHF anomaly to have regional and temporal influences.

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