Anomalous Geomagnetic Variations Possibly Linked with the Taiwan Earthquake Mw= 6.4, 19 December...
-
Upload
augustine-singleton -
Category
Documents
-
view
214 -
download
0
Transcript of Anomalous Geomagnetic Variations Possibly Linked with the Taiwan Earthquake Mw= 6.4, 19 December...
Anomalous Geomagnetic Variations Possibly Linked with the Taiwan
Earthquake Mw= 6.4, 19 December 2009
Takla E. M1; K. Yumoto1, 2; J. Y. Liu3; Y. Kakinami3; T. Uozumi2; S. Abe2 and A. Ikeda2
[1] Dept. of Earth and Planetary Sci., Kyushu University, Japan. [2] Space Environment Research Center, Kyushu University, Japan. [3] Institute of Space Science, National Central University, Taiwan.
Outline
Introduction Aim of StudyThe Tectonic Setting of TaiwanData Analysis and ResultsConclusion
IntroductionIntroduction
As a result of the lithospheric deformations, rock magnetic properties may change in response to either changes in the stress field (Piezomagnetic effect) or changes in the distribution and composition of fluids in the crust (Electro-kinetic effect). Both piezomagnetic and electro-kinetic effects can cause anomalous variations in the geomagnetic field. Anomalous changes in the geomagnetic field can occur in association with the seismic activities, so many researchers are trying to use these geomagnetic variations as precursors of earthquakes.
Aim of research
This study is mainly devoted to:
• Examine the behavior of the geomagnetic field recorded at HLN station in the vicinity of the seismic
event in Taiwan during December 2009.
• Find if there is any anomalous geomagnetic variation linked with the Taiwan EQ on 19 December 2009.
Aim of Study
The island of Taiwan is situated on the boundary between the Eurasian plate to the west and the Philippine Sea plate to the east, where the Philippine plate is being forced under the Eurasia plate with a northwest direction.
The Tectonic Setting of Taiwan
The Tectonic Setting Map of Taiwan (after Shyu and Chen, 1991).
The distance between the Epicenter and the HLN station is about 20 km
Hualienstation
Depth 45 km
Taiwan EQ 19 December 2009Mw= 6.4 at 13:02:16 UT
~ 20 ~20km
N
EQ epicenter
HLNAMA
HLN=Hualien AMA=Amami-Oh-shima
~900km
AMA
HLN
MAGDAS/CPMN Stations near Taiwan EQ Dec. 19,2009
PI: Prof. K. Yumoto
Data Analysis and Results
Geomagnetic data recorded at HLN station during Sep. 2009
100 nT
100 nT
100 nT
1-Short-term anomalous variation in the geomagnetic components
100 nT
100 nT
100 nT
Geomagnetic data recorded at HLN station during Oct. 2009
100 nT
100 nT
100 nT
Geomagnetic data recorded at HLN station during Dec. 2009
50 nT
50 nT
50 nT
Geomagnetic data recorded at HLN station during Dec. 2009
Geomagnetic data (HDZ) recorded at HLN and AMA stations during September 2009
Geomagnetic data (HDZ) recorded at HLN and AMA stations during December 2009
M=4.5 M=4.3EQ 19 Dec. 2009
M=6.4
The difference of the HDZ components recorded at both HLN and AMA stations (August - December 2009) night-time data
(7 PM to 5 AM local time)
Correlation plots for the night-time (7 PM to 5 AM LT) data recorded at both HLN and AMA stations during September
and December 2009
Sep
tem
ber
Dec
embe
r
Comparison of H component recorded at HLN station with the DST index
2- Co-seismic Geomagnetic Variation (about 5 nT)
The total geomagnetic field intensity (nT) recorded at HLN and AMA
3- Anomalous ULF Signal
Many studies have reported the occurrence of anomalous
electromagnetic signals in different frequency ranges that related to the seismic activities.
Ultra-Low-Frequency (ULF), electromagnetic emission is recently considered as one of the precursors of earthquakes.
We want to examine the possible occurrence of any anomalous ULF signal in the time interval preceding the seismic activity during December 2009.
Six hours average values of Pc 3 amplitude (10- 40 s) at HLN and the Polarization ratio (Z/H) Aug. 2009 - Jan. 2010
Conclusion
1. Anomalous geomagnetic variations about 10-15 nT in both horizontal and vertical components of the geomagnetic field that started about 1 week before the occurrence of the EQ and lasted for about 2 weeks
2. Co-seismic Geomagnetic Variation (about 5 nT)3. Enhancement of the Pc3 amplitude a few days before the onset of the
EQ and lasted for about 2 weeks.4. A small change of the polarization ratio of the Pc3 (Z/H) at HLN
started a few days before the onset of the EQ.
The observed anomalous geomagnetic variations may be connected to the seismic activity at the subduction zone near the HLN station. The changes in the crustal stress (the process of accumulation and release of stress) can cause variations in the intensity and/or rotation of the geomagnetic vectors as well as the enhancement of the conductivity structure of the lithosphere.
Thank you ありがとうございまし
た