Preminary Results of the iSTEP Program on Integrated Search for Taiwan Earthquake Precursors

Abstract

ABSTRACT1 Institute of Geophysics, National Central University, Chung-Li, Taiwan, ROC The predictability of earthquakes has been a hotly debated question in earthquake science for some time. The answer to which begs another question, "Are there credible earthquake precursors?" Intrigued by these questions and encouraged by instrumental observations of conspicuous ionospheric and geomagnetic disturbances before the disastrous 1999 Chi-Chi earthquake, we decided to undertake an integrated Search for Taiwan Earthquake Precursors, called the iSTEP program. The multidisciplinary program includes five major components aimed at identifying potential seismological, geomagnetic, geodetic and ionospheric precursors, and statistical testing of any identified precursors. Since the program's inception in April 2002, some encouraging preliminary results have been obtained. These includes precursory P wave travel-time changes six years before the Chi-Chi earthquake, identifiable geomagnetic changes two years before M ≥ 6 earthquakes, consistent ionospheric anomalies three days before M ≥ 5 earthquakes. We have also developed high-resolution radar interferometric methods for monitoring crustal deformation. A method for forecasting aftershock distribution on the basis of stress transfer has also been successfully tested on the Chi-Chi earthquake sequence. Aided by the newly installed geomagnetic and ionospheric networks we are hopeful about identifying more earthquake precursors and developing relevant physical mechanisms in the remaining two years of the iSTEP program.

Statistical Tests for Pre-earthquake Ionospheric Anomaly

“…The ionospheric anomaly is one of several possible precursors of Taiwan's earthquakes under investigation by Tsai et al (2003). According to the simulation-based tests together with reasonable criteria under study, we show that 1 -5 day alarms before M ≥ 5.0 earthquakes in the Taiwan area during 1994 -1999 on the basis of the foF2 anomalies reported in Liu et al (2003) is not due to random chance.…”

Geospace perturbations induced by the Earth: The state of the art and future trends

“…1 shows a sketch of the concept of integrated (ground and satellite) earthquake monitoring system which can be put in practice by means of different kinds of satellites/payloads. One of the preliminary attempts to apply this integrated approach systematically has been within the iSTEP Program (Tsai et al, 2004).…”

“…The sketch of the concept of integrated (ground and satellite) earthquake monitoring system (adapted fromTsai et al, 2004). The shown satellites are examples of past, present or future space missions.…”

Ultra-low-frequency (ULF) and total electron content (TEC) anomalies observed at Agra and their association with regional earthquakes

“…The extensive use of ground based ionosonde and satellite radio beacons has been made for observing ionospheric variations related to earthquakes. By these techniques the changes in the ionospheric parameters, like the greatest plasma frequencies in the ionospheric F2 region (foF2) and E region (foEs), TEC, and characteristics of turbulence have been examined to understand their earthquake induced behaviour (Liu et al, 2000;Singh and Singh, 2004;Tsai et al, 2004).…”