Seismo-geomagnetic anomalies and M⩾ 5.0 earthquakes observed in Taiwan during 1988–2001

Liu, J.Y.; Chen, C.H.; Chen, Y.I.; Yen, Horng Yuan; Hattori, Katsumi; Yumoto, K.

doi:10.1016/j.pce.2006.02.009

Cited by 44 publications

(32 citation statements)

References 7 publications

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“…As to the mismatch in the case of EQ16, it may be caused by the fact, that EQ16 is the only event with a normal faulting focal mechanism, whereas the other 15 events are of reverse faulting or strike-slip type. Liu et al (2006) suggested that seismo-magnetic anomalies are often observed in reversed fault or strike-slip earthquakes because of the discrepancy of earthquake-related stress accumulation. …”

Section: Methodsmentioning

confidence: 99%

“…Recognition of anomalous pre-earthquake phenomena has been reported for major earthquakes since 1990 (Fraser-Smith et al, 1990;Bernardi et al, 1991;Molchanov et al, 1992;Kopytenko et al, 1993;Lin and Zeng, 1992;Hayakawa et al, , 1999Hayakawa et al, , 2000Kawate et al, 1998;Gotoh et al, 2002;Hattori et al, 2002Hattori et al, , 2004aHattori, 2004;Liu et al, 2006;Molchanov and Hayakawa, 2008;Chen et al, , 2011Han et al, 2011;Wen et al, 2012). These reports indicate that geomagnetic anomalies prior to earthquakes are caused by either momentary existence of earthquake-related high conductivity materials or the movement of electric current along faults (Zeng et al, 1995;Merzer and Klemperer, 1997;Yen et al, 2004).…”

Section: Introductionmentioning

confidence: 96%

“…A 3-component fluxgate magnetometer (the CCU station, 120.47 • E, 23.56 • N, Fig. 1) with a 1 Hz sampling rate was installed in central Taiwan in 2002 (Liu et al, 2006). The data gathered at the CCU station are utilised to investigate subsurface electric and/or magnetic features and to further study the seismo-electromagnetic anomalies in this complex area.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of seismo-electric anomalies using magnetic data in Taiwan

Chen

Hsu

Wen

et al. 2013

Nat. Hazards Earth Syst. Sci.

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The Parkinson vectors derived from 3-component geomagnetic data via the magnetic transfer function are discussed with respect to epicentre locations and hypocentre depths of 16 earthquakes (M ≥ 5.5) in Taiwan during a period of 2002–2005. To find out whether electric conductivity changes would happen particularly in the seismoactive depth ranges, i.e. in the vicinity of the earthquake foci, the frequency dependent penetration depth of the electromagnetic waves (skin effect) is taken into account. The background distributions involving the general conductivity structure and the coast effect at 20 particular depths are constructed using the Parkinson vectors during the entire study period. The background distributions are subtracted from the time-varying monitor distributions, which are computed using the Parkinson vectors within the 15-day moving window, to remove responses of the coast effect and underlying conductivity structure. Anomalous depth sections are identified by deviating distributions and agree with the hypocentre depths of 15 thrust and/or strike-slip earthquakes with only one exception of a normal fault event

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Evaluation of seismo-electric anomalies using magnetic data in Taiwan

Chen

Hsu

Wen

et al. 2013

Nat. Hazards Earth Syst. Sci.

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“…Timings and/or locations of forthcoming earthquakes can be effectively estimated by using FFT (Fraser-Smith et al, 1990), the fractal method , the flicker noise spectroscopy (Hayakawa and Timashev, 2006), the radiometric method (Kopytenko et al, 2001), and the principle component analysis (Hattori et al, 2004b) as well as anomalous daily variation ranges (Liu et al, 2006). Hattori (2004) summarized empirical observations from many major earthquakes, and found that the distance of the success detection for ULF emission waves is proportional to earthquake magnitude.…”

Section: Discussionmentioning

confidence: 99%

“…Chen et al (2009a) prudently examined data quality of the 11 stations by the Chapman-Miller method (Chapman and Miller, 1940), and found that tiny signals caused by the magnetic lunar effects can be observed. Although these total intensity data retrieved from this network are difficult to be used to observe changes in direction of magnetic fields, good quality and a long observation period (from 1988 to now) of data are sufficient to be utilized in most geomagnetic studies (Chen et al, , 2009a(Chen et al, , 2010(Chen et al, , 2011aLiu et al, 2006;Yen et al, 2004Yen et al, , 2009). The M = 9.0 Tohoku earthquake (142.38 • E, 38.30 • N) occurred on 11 March 2011, striking northern and eastern Japan as the most destructive earthquake thus far in the 21st century.…”

Section: Introductionmentioning

confidence: 99%

Magnetic storm free ULF analysis in relation with earthquakes in Taiwan

Wen

Chen

Yen

et al. 2012

Nat. Hazards Earth Syst. Sci.

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Abstract. Despite early optimism, pre-earthquake anomalous phenomena can be determined by using enhanced amplitude at the ultra-low-frequency range from geomagnetic data via the Fourier transform. In reality, accuracy of the enhanced amplitude in relation to earthquakes (deduced from time-varied geomagnetic data) would be damaged by magnetic storms and/or other unwanted influences resulting from solar activity and/or variations in the ionosphere, respectively. We substitute values of the cross correlation between amplitudes, summarized from the earthquake-related (0.1-0.01 Hz) and the comparable (0.01-0.001 Hz) frequency bands, for isolated amplitude enhancements as indexes of determination associated with seismo-magnetic anomalies to mitigate disturbance caused by magnetic storms. A station located about 300 km away from the others is also taken into account to further examine whether changes of the cross correlation values are caused by seismo-magnetic anomalies limited within local regions or not. Analytical results show that the values suddenly decrease near epicenters a few days before and after 67 % (= 6/9) of earthquakes (M > = 5) in Taiwan between September 2010 and March 2011. Seismomagnetic signals determined by using the values of cross correlation methods partially improve results yielded from the Fourier transform alone and provide advantageous information of earthquake locations.

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A statistical study on ELF‐whistlers/emissions and M ≥ 5.0 earthquakes in Taiwan

et al. 2013

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. Occurrence ratios of the ELF-whistler and ELF-emission of the entire study period are computed as the reference backgrounds. Our study shows that the ELF-whistlers and ELF-emissions during the earthquake period appear less and more frequently than their associated backgrounds, respectively. For the ELF-emission, the larger earthquakes generally yield the higher occurrence ratios. The statistical analyses confirm that the occurrence ratios of the ELF-emission significantly enhance 5-7 days before the earthquakes and are proportional to the earthquake magnitude but inversely to the distance from the observatory to the epicenter.

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Seismo-geomagnetic anomalies and M⩾ 5.0 earthquakes observed in Taiwan during 1988–2001

Cited by 44 publications

References 7 publications

Evaluation of seismo-electric anomalies using magnetic data in Taiwan

Evaluation of seismo-electric anomalies using magnetic data in Taiwan

Magnetic storm free ULF analysis in relation with earthquakes in Taiwan

A statistical study on ELF‐whistlers/emissions and M ≥ 5.0 earthquakes in Taiwan

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