電離層地震前兆( I );Seismo-Ionospheric Precursor( I )

NCUIR > College of Earth Sciences > Graduate Institute of Space Science > Research Project > Item 987654321/62455

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/62455

Title:	電離層地震前兆( I );Seismo-Ionospheric Precursor( I )
Authors:	劉正彥;陳玉英;蔡和芳
Contributors:	國立中央大學太空科學研究所
Keywords:	地球科學
Date:	2012-12-01
Issue Date:	2014-03-17 11:33:03 (UTC+8)
Publisher:	行政院國家科學委員會
Abstract:	研究期間：10108~10207;Recently seismo-ionospheric precursors (SIPs) have been intensively studied. After the 21 September 1999 M7.6 Chichi Earthquake, 8 comprehensive ground-based observation networks have been constructed and routinely operated to search seismo-anomalous signals (SASs) in Taiwan by the iSTEP (integrated Search for Taiwan Earthquake Precursors) project since 2003. Based on the existing achievements and progresses, this project plans to continue and extend the iSTEP to uncover the link among SASs in the lithosphere, atmosphere, and ionosphere before large earthquakes in Taiwan, and to utilize the observed SIPs and SASs developing systems for earthquake hazard assessments and the earthquake prediction/forecast in regions and the globe. Both ground- and satellite-based observations are employed to detect the SIPs/SASs, while statistical and physical models will be constructed to conduct the earthquake hazard assessments and to find the associated mechanisms. This integrated project consists of a main project and two sub-projects. The main project carries out statistical developments to identify SASs/SIPs and conducts model simulations to understand causal mechanisms of the lithosphere-atmosphere-ionosphere coupling (LAIC) processes. Based on the developed statistical references and simulated characteristics, the two sub-projects identify SASs/SIPs and find possible forthcoming earthquakes. Sub-project 1 monitors SASs in the lithosphere, atmosphere, and ionosphere, and solely predicts possible forthcoming earthquakes in the Taiwan area. Meanwhile, it provides data to the main project for conducting physical model simulations, and gives a flag to Sub-project 2 for further searching and confirming the predicted forthcoming earthquakes. Sub-project 2 constructs regional and global maps of ionospheric GPS TEC (total electron content) and analyzes temporal and spatial SIPs to solely predict the occurrence time and location of forthcoming large earthquakes. The temporal variation and spatial distribution of the observed SIPs are given to the main project for physical model simulations and to Sub-project 1 for understanding the LAIC link. Although focusing on earthquake precursors, this project also examines disturbances in the observables triggered by large earthquakes and tsunami. Comparisons between the SIPs/SASs and seismic disturbances allow us have a better understanding the related causal mechanisms. Main project Many seismo-electromagnetic signal (SES) features of anomalous electromagnetic fields/emissions, electron density, and total electron content (TEC) before large earthquakes have been reported. These features imply that the electromagnetic parameters of the electric potential, electric field, electric current, magnetic field, etc. in the lithosphere and atmosphere and ionosphere around the epicenter generated during the earthquake preparation period are essential. The main project shall impose/insert the parameters of the lithosphere and atmosphere into the existing ionosphere physical models to simulate temporal variations and spatial structure of the ionospheric electron density and TEC. The comparison between the simulated and observed SIPs shall allow us find the dynamics and physical mechanisms of the LAIC link. The previous 15-day running median and associated upper/lower bound have been used as a reference detecting the SIPs, SESs, and SASs. However, the median base reference still occasionally suffers from seasonal effects. The main project shall conduct a series of statistical tests to find an optimal reference to have a better detection on SIPs, SESs, and SASs, as well as to enhance the successes rate but decrease the failure rate (also the false alarm rate). Sub-project 1 Sub-project-1 shall continue operating 11 existing observation iSTEP (iSTEP-1: 2003/4-2007/3; iSTEP-2: 2007/8-2012/7) networks and expand by adding 2 ground-based and 2 satellites (space-based) observations monitoring SASs of the lithosphere, atmosphere, and ionosphere in Taiwan. Each observed SAS could be solely used as a precursor for either short-, mid-, or long-term earthquake hazard assessment. The existing networks consists of magnetometers, electrode arrays, infrasonic systems, corona probes, field mills, FM tuners, VHF beacon, Doppler sounding systems, ionosondes (ionospheric HF radars), GPS receivers, and all sky cameras. The 2 newly added ground-based observations are the surface displacement by GPS receivers and groundwater level of wells, while FORMOSAT-3/ COSMIC (F3/C; also FORMOSAT-7) and FORMOSAT-5 are used to monitor the electron density and plasma in the ionosphere, respectively. Networks of the GPS receivers and wells monitor the stress and surface displacement, respectively. The magnetometer and electrode probe SES in the lithosphere. The infrasonic system records acoustic gravity (or atmospheric pressure) waves. The corona probes and field mill detects atmospheric electric fields. The FM tuner and VHF beacon register irregularities in the lower ionosphere. The Doppler sounding system observes ionospheric waves. The ionosondes measure the ionospheric electron density profile. The ground-based GPS receivers observe the ionospheric TEC, and the all sky camera images traveling ionospheric disturbances. F3/C (also FORMOSAT-7) provides the 3-D electron density structure, while FORMOSAT-5 records the ionospheric plasma density, velocity, and temperature. Therefore, the integrated observation of Sub-project 1 shall be the most comprehensive SAS network of the world, which allows us conducting detailed LAIC monitoring during the earthquake preparation period. Note that the newly introduced FORMOSAT-3, -5, and -7 carry out global observations which therefore can also be used to search SIPs of worldwide earthquakes and support pre-earthquake studies in foreign countries. Sub-project 2 Recently, the global ionospheric map (GIM) of TEC has been used to study SIPs intensively. However, the GIM provided by international data centers usually has a latency of about 1-4 days. To timely serve the SIP study, Sub-project 2 retrieves measurements of global-based GPS networks to compute the TEC and construct a real-time GIM. The GIM TEC is employed to discriminate global effects (such as magnetic storms) and local effects (such as earthquakes) as well as to find the temporal and spatial SIPs of worldwide large earthquakes. A temporal statistical analysis is developed to detect the SIPs and to compute the chance of earthquake occurrence at certain location (earthquake hazard assessment). A spatial analysis is further conducted on GIM TEC data finding the repeat, duration, and distribution of worldwide SIPs to locate possible forthcoming large earthquakes. Although being suitable to detect worldwide earthquakes, the GIM is too coarse in spatial resolution to detect smaller earthquakes in a certain region such as Taiwan. Taiwan currently yields a dense GPS network. Therefore, this sub-project shall collect local ground-based GPS data to construct regional ionospheric map (RIM) with much higher spatial resolution for precisely detecting temporal and spatial SIPs as well as conduct earthquake hazard assessment in Taiwan in real time.
Relation:	財團法人國家實驗研究院科技政策研究與資訊中心
Appears in Collections:	[太空科學研究所 ] 研究計畫

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