2008年汶川地震前电离层异常研究
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摘要
利用FORMOSAT-3/COSM IC提供的2007—2010年掩星剖面数据,研究汶川Mw7.9地震前,孕震区及磁共轭区上空电离层的变化。研究表明,震前5天内(5月7—11日),孕震区电离层F2层最大电子密度NmF2值在4:00—8:00UT(12:00—16:00LT)相对于震前6~17天(4月25—5月6日)明显减小,幅度达(2~4)×105el/cm3。另外,取2007—2010年(不包括2008年)5月7—11日下午12:00—14:00LT孕震区上空的NmF2值作为多年背景值,发现2008年震前5天的NmF2值相对多年同时段背景值明显减小,幅度为(2~4)×105el/cm3。并且在孕震区对应的磁共轭区也有与上述类似的现象出现。
On 12 May 2008 at 06:28UT a major earthquake of M w 7.9 struck Wenchuan County(31.0°N,103.4°) in China.Occultation profiles derived from FORMOSAT-3/COSMIC between 2007 and 2010,were used to investigate the ionoshperic precursor of the Wenchuan earthquake area and magnetic conjugate area.Relative to the NmF2(F2-peak electron density) of 6-17 days(25 April-6 May) prior to earthquake,it has been determined that near the epicenter the NmF2,decreased during 04:00-08:00UT(12:00-16:00LT) within 5 days(7-11 May) prior to the earthquake,and the maximum deviation was about(2-4)×10 5 el/cm 3.Furthermore we choose the NmF2 data derived from 3 years(12:00-14:00LT,7-11 May,2007-2010,except 2008) as background value.The NmF2 5 days prior to earthquake was lower than background value.The maximum deviation was about(2-4)×10 5 el/cm 3.And there was similar phenomenon detected in magnetic conjugate area.
On 12 May 2008 at 06:28UT a major earthquake of M w 7.9 struck Wenchuan County(31.0°N,103.4°) in China.Occultation profiles derived from FORMOSAT-3/COSMIC between 2007 and 2010,were used to investigate the ionoshperic precursor of the Wenchuan earthquake area and magnetic conjugate area.Relative to the NmF2(F2-peak electron density) of 6-17 days(25 April-6 May) prior to earthquake,it has been determined that near the epicenter the NmF2,decreased during 04:00-08:00UT(12:00-16:00LT) within 5 days(7-11 May) prior to the earthquake,and the maximum deviation was about(2-4)×10 5 el/cm 3.Furthermore we choose the NmF2 data derived from 3 years(12:00-14:00LT,7-11 May,2007-2010,except 2008) as background value.The NmF2 5 days prior to earthquake was lower than background value.The maximum deviation was about(2-4)×10 5 el/cm 3.And there was similar phenomenon detected in magnetic conjugate area.
引文
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14 Liu J Y,et al.Ionosphericf0F2and TEC anomalous daysassociated with M C 5.0 earthquakes in Taiwan during1997-1999[J].Terr Atmos Ocean Sci.,2004,15:371-383.
15 Liu J Y,et al.Pre-earthquake ionospheric anomalies regis-tered by continuous GPS TEC measurement[J].Ann Geo-physicae,2004,22:1 585-1 593.
16 Dobrovolsky I R,Zubkov S I and Myachkin V I.Estima-tion of the size of earthquake preparation zones[J].Pure&Applied Geophysics,1979,117:1 025-1 044.
17 Freund F.Time-resolved study of charge generation andpropagation in igneous rocks[J].Journal of GeophysicalResearch,2000,105:11 001-11 019.
18 Kim V P and Hegai V V.A possible presage of strongearthquakes in the night-time mid-latitude F2 region iono-sphere[A].M Hayakawa(Ed.).Atmospheric and iono-spheric electromagnetic phenomena associated with earth-quakes[C].Tokyo:Terra Science Publishing Co.,1999,619-627.
19 Pulines S A,et al.Quasielectrostatic model of atmosphere-thermosphere-ionosphere coupling[J].Advances in SpaceResearch,2000,26:1 209-1 218.
2 Chen Y I,et al.Statistical tests for pre-earthquake iono-spheric anomaly[J].Terr Atmos Ocean Sci.,2004,15:385-396.
3 Liu J Y,et al.Variations of ionospheric total electron contentduring the Chi-Chi earthquake[J].Geophysical ResearchLetters,2001,28:1 383-1 386.
4 Pulinets S Aand Legen’ka AD.Spatial-temporal character-istics of large scale distributions of electron density observedin the ionospheric F-region before strong earthquakes[J].Cosmic Research,2003,41:221-229.
5 Dautermann T,et al.Investigation of ionospheric electroncontent variations before earthquakes in southern California,2003-2004[J].Journal of Geophysical Research,2007,112:B02106.
6 Hsiao C C,et al.Seismo-ionospheric precursor of the 2008Mw7.9 Wenchuan earthquake observed by FORMOSAT-3/COSMIC[J].GPS Solut.,2010,14:83-89.
7 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:A11304.
8 Pulinets S A and Boyarchuk K.Ionospheric precursors ofearthquakes[M].New York:Springer,2004.
9 Liu J Y,et al.Seismoionospheric GPS total electron contentanomalies observed before the 12 May 2008Mw7.9 Wen-chuan earthquake[J].Journal of Geophysical Research,2009,114:A04320.
10 Rocken C,et al.COSMIC system description[J].Terr At-mos Ocean Sci.,2000,11(1):21-52.
11 Schreiner W,et al.Estimates of the precision of GPS radiooccultations from the COSMIC/FORMOSAT-3 mission[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 Jhuang H K,et al.Seismo-ionospheric anomalies of theGPS-TEC appear before the 12 May 2008 magnitude 8.0Wenchuan Earthquake[J].International Journal of RemoteSensing,2010,31:3 579-3 587.
14 Liu J Y,et al.Ionosphericf0F2and TEC anomalous daysassociated with M C 5.0 earthquakes in Taiwan during1997-1999[J].Terr Atmos Ocean Sci.,2004,15:371-383.
15 Liu J Y,et al.Pre-earthquake ionospheric anomalies regis-tered by continuous GPS TEC measurement[J].Ann Geo-physicae,2004,22:1 585-1 593.
16 Dobrovolsky I R,Zubkov S I and Myachkin V I.Estima-tion of the size of earthquake preparation zones[J].Pure&Applied Geophysics,1979,117:1 025-1 044.
17 Freund F.Time-resolved study of charge generation andpropagation in igneous rocks[J].Journal of GeophysicalResearch,2000,105:11 001-11 019.
18 Kim V P and Hegai V V.A possible presage of strongearthquakes in the night-time mid-latitude F2 region iono-sphere[A].M Hayakawa(Ed.).Atmospheric and iono-spheric electromagnetic phenomena associated with earth-quakes[C].Tokyo:Terra Science Publishing Co.,1999,619-627.
19 Pulines S A,et al.Quasielectrostatic model of atmosphere-thermosphere-ionosphere coupling[J].Advances in SpaceResearch,2000,26:1 209-1 218.
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