用BP神经网络技术探测汶川地震前电离层NmF2异常扰动
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摘要
基于UCAR公布的电离层F2层最大电子密度数据NmF2,利用人工神经网络技术,构建局部地区NmF2模型。以年积日DOY、当地时LT、经度LON、纬度LAT和F10.7太阳活动指数FLUX为网络输入,以NmF2为网络输出,提供磁平静期NmF2模型值作为参考背景,通过模型值与观测值的比较,发现2008年5月12日汶川7.9级地震前震中附近上空NmF2在震前第6～4天(6—8日)减小约30%,震前第3～2天(9—10日)明显增大约40%。
On the basis of the F2 layer peak electron density(NmF2) from University Corporation for Atmospheric Research(UCAR),we constructed a Back Propogation(BP) artificial neural network(ANN) in order to detect pre-earthquake anomalies for the first time.The ANN provides NmF2 model value with five parameters:DOY,local time(LT),longitude(LON),latitude(LAT) and solar activity index of F10.7(FLUX).We compare the model value with observations during the Wenchuan earthquake.It is found that NmF2 around the forthcoming epicenter decreased remarkably in the afternoon period of day 6-4 before the earthquake,but enhanced day 3-2 before the earthquake.
On the basis of the F2 layer peak electron density(NmF2) from University Corporation for Atmospheric Research(UCAR),we constructed a Back Propogation(BP) artificial neural network(ANN) in order to detect pre-earthquake anomalies for the first time.The ANN provides NmF2 model value with five parameters:DOY,local time(LT),longitude(LON),latitude(LAT) and solar activity index of F10.7(FLUX).We compare the model value with observations during the Wenchuan earthquake.It is found that NmF2 around the forthcoming epicenter decreased remarkably in the afternoon period of day 6-4 before the earthquake,but enhanced day 3-2 before the earthquake.
引文
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15 Liu J Y,et al.Ionospheric foF2 and TEC anomalous daysassociated with M≥5.0 earthquakes in Taiwan during 1997-1999[J].Terr Atmos Oceanic Sci.,2004,15:371-383.
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17 Bolt B A.Earthquake(4th ed)[M].New York,1999.
18 Freund F.Time-resolved study of charge generation andpropagation in igneous rocks[J].J Geophys Res.,2000,105:11001-11019.
2 Liu J Y,et al.Chuo,seismo-ionospheric signatures prior to M≥6.0 Taiwan earthquakes[J].Geophys Res Lett.,2000,27:3113-3116.
3 Liu J Y,et al.Variations of ionospheric total electron contentduring the Chi-Chi earthquake[J].Geophys Res Lett.,2001,28:1381-1386.
4 Pulinets S and Boyarchuk K.Ionospheric precursors of earth-quakes[M].Berlin:Springer,2004.
5 Liu J Y,et al.Temporal and spatial precursors in the iono-spheric global positioning system(GPS)total electron con-tent observed before the 26 December 2004 M9.3 Sumatra-Andaman earthquake[J].Journal of Geophysical Research,2010,115:A09312.
6 Zhao B Q,et al.Is an unusual large enhancement of iono-spheric electron density linked with the 2008 great Wen-chuan earthquake?[J].Jounal of Geophysical Research,2008,113:A11034.
7 Liu J Y,et al.Seismoionospheric GPS total electron contentanomalies observed before the 12 May 2008 Mw7.9 Wen-chuan earthquake[J].Journal of Geophysical Research,2009,114:A04320.
8 Zhou Y Y,et al.Ionospheric anomalies detected by ground-based GPS before the Mw7.9 Wenchuan earthquake of May 12,2008,China[J].Journal of Atomospheric and Solar-ter-restrial Physics,2009,959-966.
9 Lin J,et al.Wenchuan earthquake ionosphere TEC anomalydetected by GPS[J].Chinese Journal of Geophysics,2009,52(1):297-300.
10 KosukeHeki.Ionospheric electron enhancement precedingthe 2011 Tohoku-Oki earthquake[J].Geophysical ResearchLetters,2011,38:L17312.
11 Schreiner W,et al.Estimates of the precision of GPS radiooccultations from the COSMIC/FORMOSAT-3mission[J].Geophys Res Lett.,2007,34:L04808.
12 Lei J,et al.Comparison of COSMIC ionospheric measure-ments with ground-based observations and model predic-tions:preliminary results[J].J Geophys Res.,2007,112:A07308.
13 Rocken C,et al.COSMIC system description[J].Terr At-mos Ocean Sci.,2000,11(1):21-52.
14 Liu J Y,et al.Variations of ionospheric total electron con-tent during the Chi-Chi earthquake[J].Geophys Res Lett.,2001,28:1381-1386.
15 Liu J Y,et al.Ionospheric foF2 and TEC anomalous daysassociated with M≥5.0 earthquakes in Taiwan during 1997-1999[J].Terr Atmos Oceanic Sci.,2004,15:371-383.
16 Liu J Y,et al.Pre-earthquake ionospheric anomalies regis-tered by continuous GPS TEC measurements,Ann[J].Geophys.,2004,22:1585-1593.
17 Bolt B A.Earthquake(4th ed)[M].New York,1999.
18 Freund F.Time-resolved study of charge generation andpropagation in igneous rocks[J].J Geophys Res.,2000,105:11001-11019.
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