International Conference on Mathematics and Natural Sciences, 2008 , ITB
Some results of seismo-electromagnetic research at LAPAN, Indonesia
National Institute of Aeronautics and Space (LAPAN), Indonesia
Indonesia is recognized as one of the most tectonically active regions in the world. This is evident in the number of earthquakes experienced by the country annually. Every year, Indonesia suffers extensive damage and loss of human life from earthquakes. To mitigate death and destruction on the islands of Indonesia, it is necessary that a way of making a “forecast” for earthquakes be developed. Recently, seismo-electromagnetic phenomena have been considered a promising tool for monitoring seismic activity. The presence of such precursory signature related to strong earthquakes has been identified in the ionospheric perturbations and anomalous ULF geomagnetic field change. There has been a good deal of accumulated and convincing evidence of ionospheric perturbations and ULF magnetic signatures before strong earthquakes as reported in the previous studies. Studies related with ionospheric precursors of the earthquakes in Indonesia using the TEC (Total Electron Content) data and the pre-earthquake ULF geomagnetic anomalies are carried out at LAPAN in collaboration with Chiba University, The University of Electro-Communications, Nagoya University, Kyushu University, NCU Taiwan, LIPI, BMG, and Bakosurtanal. Case studies are carried out in this work to investigate the ionospheric precursors of the earthquakes and the pre-earthquake ULF geomagnetic anomalies during the Aceh earthquake on December 26, 2004 (magnitude Mw= 9.0 and depth = 30 km from USGS catalog), and Nias earthquake of March 28, 2005 (Mw= 8.7 and depth = 30 km). It has been found that the ionospheric anomalies appear a few days prior to earthquakes and seismic activity is possible source of the ionospheric anomalies. To investigate the pre-earthquake ULF geomagnetic anomalies, the polarization analysis and transfer functions analysis based on wavelet transform method have been applied to the observed data. Results of polarization analysis show similar variation of those of amplitude for induction arrow in transfer function analysis. These variations at Kototabang exhibit an anomalous changes a few weeks before the strong earthquakes with M>6.5, while there are no apparent changes in Biak data. This suggests that the anomalous change might be a possible signal related with the earthquake preparation phase of Sumatra earthquakes. Applying various methods with multiple independent instruments for the same event or at the same time as a hopeful way to make results more convincing and to increase robustness of anomalous changes associated with earthquakes.
Ionospheric Perturbations, Anomalous ULF Geomagnetic Field