Use of resistivity measurements to detect urban caves in Mexico City and to assess the related hazard

ULF emission data at Lunping (epicentral distance, 120 km) have been analysed for the Chi-chi earthquake (with magnitude 7.6 and depth of 11 km) in Taiwan which occurred on 21 September 1999. Simple intensity analyses have not yielded any significant results but we have found, based on the analysis of polarization (the ratio of vertical magnetic field component Z to the horizontal component G), that the polarization ( Z/G) showed a significant enhancement for two months before the earthquake. This kind of temporal evolution of polarization seems to be very similar to previous results, so that it is highly likely that this phenomenon may be associated with the Chi-Chi earthquake. Also, the comparison of the results of polarization analyses, by changing the signal threshold, has given us an approximate intensity of the seismogenic emission of the order of the monthly mean value.

[1]  早川 正士,et al.  Electromagnetic phenomena related to earthquake prediction , 1994 .

[2]  Masashi Hayakawa,et al.  Fractal analysis of ULF geomagnetic data associated with the Guam Earthquake on August 8, 1993 , 1999 .

[3]  Takao Saito,et al.  Geomagnetic pulsations , 1969 .

[4]  Enrique Gómez-Treviño.  Nonlinear integral equations for electromagnetic inverse problems , 1987 .

[5]  M. Ladd,et al.  Low‐frequency magnetic field measurements near the epicenter of the Ms 7.1 Loma Prieta Earthquake , 1990 .

[6]  G. W. Hohmann.  Three-Dimensional Induced Polarization and Electromagnetic Modeling , 1975 .

[7]  Masashi Hayakawa,et al.  Generation of ULF electromagnetic emissions by microfracturing , 1995 .

[8]  Kiyohumi Yumoto,et al.  ULF electromagnetic precursors for an earthquake at Biak, Indonesia on February 17, 1996 , 2000 .

[9]  Masashi Hayakawa,et al.  Atmospheric and ionospheric electromagnetic phenomena associated with earthquakes , 1999 .

[10]  R. Barker,et al.  Rapid least-squares inversion of apparent resistivity pseudosections , 1994 .

[11]  Masashi Hayakawa,et al.  Ultra-low-frequency magnetic fields during the Guam earthquake of 8 August 1993 and their interpretation , 1998 .

[12]  M. Hayakawa,et al.  Penetration characteristics of electromagnetic emissions from an underground seismic source into the atmosphere, ionosphere, and magnetosphere , 1995 .

[13]  M. A. Pérez-Flores,et al.  Imaging low-frequency and dc electromagnetic fields using a simple linear approximation , 2001 .

[14]  G. Golub,et al.  Linear least squares and quadratic programming , 1969 .

[15]  KEPING CHEN,et al.  Towards an Integrated Approach to Natural Hazards Risk Assessment Using GIS: With Reference to Bushfires , 2003, Environmental management.

[16]  D. Oldenburg,et al.  3-D inversion of induced polarization data , 2001 .

[17]  Yu. A. Kopytenko,et al.  Results of ULF magnetic field measurements near the epicenters of the Spitak (Ms = 6.9) and Loma Prieta (Ms = 7.1) earthquakes: Comparative analysis , 1992 .

[18]  Kiyohumi Yumoto,et al.  Results of ultra-low-frequency magnetic field measurements during the Guam Earthquake of 8 August 1993 , 1996 .

[19]  Yutaka Sasaki,et al.  Two‐dimensional joint inversion of magnetotelluric and dipole‐dipole resistivity data , 1989 .

[20]  M. Gokhberg,et al.  Experimental measurement of electromagnetic emissions possibly related to earthquakes in Japan , 1982 .