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Ionospheric Total Electron Content (TEC) Anomalies Associated with Earthquakes through Karhunen-Loéve Transform (KLT)

2010; Springer Nature; Volume: 21; Issue: 2 Linguagem: Inglês

10.3319/tao.2009.06.11.01(t)

2311-7680

Jyh‐Woei Lin,

Seismology and Earthquake Studies

STRACTThis re search uses eigenvalue char ac ter is tics of the Karhunen-Loéve Trans form of ion o spheric to tal elec tron con tent (TEC) to in ves ti gate pre cur sors for 12 earth quakes of Rich ter mag ni tude scale M ³ 5.0 in a lo cal re gion of lat i tude 23.00 to 24.00°N and lon gi tude 120.00 to 121.50°E for 1 January 2002 to 31 December 2003.Pre vi ous re search ers have found that in the 5 days be fore these earth quakes (i.e., prior to M ³ 5.0), pre cur sors of clear ion o spheric anom a lies show ing sparser to tal elec tron con tent (TEC) were de tected through sta tis ti cal in ves ti ga tion.This was ev i denced through two is sues from Liu and his part ners in 2001 and 2006.These is sues gave cred i ble ev i dence of such pre cur sors.The pre cur sor days hav ing clear ex treme eigenvalues of the Karhunen-Loéve Trans form as the pre cur sors in stead of the sparser ion o spheric TEC were also mostly in the 5 days be fore the 12 earth quakes of greater than M ³ 5.0.The pre cur sors of Chi-Chi Earth quake (M w = 7.6) with clear ex treme eigenvalues were de tected on the 1 st , 3 rd , and 4 th days be fore this earth quake.These re sults are con sis tent with the anal y ses of Liu and his part ner's is sue in 2001.These find ings ver ify the va lid ity of the Karhunen-Loéve Trans form.To fur ther ver ify this ap proach, the Karhunen-Loéve Trans form is ap plied to an earth quake in Ja pan.Pre cur sors to the Ja pan Iwate-Miyagi Nairiku earth quake (M j = 7.2), with clear ex treme eigenvalues are de tected on the 1 st , 2 nd , and 5 th days be fore the earth quake, re spec tively.How ever, af ter de tailed anal y sis, pre cur sors of earth quakes of Rich ter mag ni tude scale M < 5 are not easy to identify using extreme eigenvalues because of existence of other ionospheric features not caused by earthquakes.