Magnitude determination of Mexican earthquakes
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Abstract
We explore two alternative magnitude scales, MA and ME, for quasi-real time estimate of magnitude of moderate and _ large Mexican earthquakes using broadband recordings at Ciudad Universitaria (CU), Mexico D.F., Mexico. MA and ME are based on amplitude of band-pass filtered (between 15 and 30 sec) velocity traces and estimate of radiated seismic energy, respectively. Both scales are tied to the moment magnitude, Mw. MA is adequate for shallow, moderate, and large earthquakes, but appears to saturate for major and great earthquakes. ME, on the other hand, does not suffer from saturation and should be valid for events of all depths. In as much as MA measures long-period characteristics of an event while the contribution to ME mostly comes from frequencies near the corner frequency of the event, the magnitude on the two scales. may differ for the same earthquake, even if MA has not saturated. Since a large disparity in the two magnitudes may be indicative of anomalous nature of an earthquake, we recommend the use of both scales whenever possible.
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References
AKI, K., 1980. Attenuation of shear-waves in the lithosphere for frequencies from 0.05 to 25 Hz. Phys. Earth Planet. Interiors 21, 50-60. DOI: https://doi.org/10.1016/0031-9201(80)90019-9
ASTIZ, L. and H. KANAMORI, 1984. An earthquake doublet in Ometepec, Guerrero, Mexico. Phys. Earth Planet. Interiors 34, 24-45. DOI: https://doi.org/10.1016/0031-9201(84)90082-7
BRUNE, J. N., 1970. Tectonic stresses and spectra of seismic waves from earthquakes. J. Geophys. Res., 75, 4997-5009. DOI: https://doi.org/10.1029/JB075i026p04997
CHAEL, E. P. and G. S. STEWART, 1982. Recent large earthquakes along the Middle America trench and their implications for the subduction process. J. Geophys. Res., 87, 329-338. DOI: https://doi.org/10.1029/JB087iB01p00329
DZIEWONSKI, A. M., T. A. CHOU and J. H. WOODHOUSE, 1981. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity. J. Geophys. Res., 86, 2825-2852. DOI: https://doi.org/10.1029/JB086iB04p02825
FIGUEROA, J., 1970. Catálogo de sismos ocurridos en Ia República Mexicana, Report No 272, Instituto de Ingeniería, UNAM, México.
HAVSKOV, J. and M. MACIAS, 1983. A coda-length magnitude scale for some Mexican stations. Geofísica Internacional, 22, 205-214. DOI: https://doi.org/10.22201/igeof.00167169p.1983.22.3.864
HERRMANN, R., 1993. Computer Programs in Seismology, Volume III, Department of Atmospheric Sciences, Saint Louis University, St. Louis, Mo.
KANAMORI, H. 1977. The Energy Release in Great Earthquakes. J. Geophys. Res., 82, 2981-2987. DOI: https://doi.org/10.1029/JB082i020p02981
KOVACH, R. L., 1978. Seismic surface waves and crustal and upper mantle structure. Rev. Geophys. Space Phys. 16, 1-13. DOI: https://doi.org/10.1029/RG016i001p00001
ORDAZ, M. and S. K. SINGH, 1992. Source spectra and spectral attenuation of seismic waves from Mexican earthquakes, and evidence of amplification in the hill zone of Mexico City. Bull. Seism. Soc. Am., 82, 24-43.
PACHECO, J., L. R. SYKES and C. SCHOLZ, 1993. The nature of seismic coupling along plate boundaries of the subduction type. J. Geophys. Res., 98, 14133-14159. DOI: https://doi.org/10.1029/93JB00349
QUAAS, R., D. ALMORA, S. K. SINGH, M. TORRES and R. VAZQUEZ, 1993. Sistema de disparo remoto para una red de acelerógrafos ADII en el Valle de México: acelerogramas en suelo duro del temblor de Mayo 15 de 1993. Memorias X Congreso Nacional de Ingeniería Sísmica, Mexico, del 8-11 de octubre de 1993, 97-111.
ROMANOWICZ, B. et al., 1991. The Geoscope program: present status and perspectives. Bull. Seism. Soc. Am., 81, 243-264. DOI: https://doi.org/10.1785/BSSA0810010243
SINGH, S. K., M. RODRIGUEZ and J. M. ESPINDOLA, 1984. A catalog of earthquakes of Mexico from 1900 to 1981. Bull. Seism. Soc. Am., 74, 267-279. DOI: https://doi.org/10.1785/BSSA0740010267
SINGH, S. K., E. MENA and R. CASTRO, 1988. Some aspects of the source characteristics and the ground motion amplification in and near Mexico City from the acceleration data of the September 1985 Michoacan, Mexico earthquakes. Bull. Seism. Soc. Am., 78, 451-477.
SINGH, S. K. and F. MORTERA, 1991. Source-time functions of large Mexican subduction zone earthquakes, morphology of the Benioff zone and the extent of the Guerrero gap. J. Geophys. Res, 96, 21487-21502. DOI: https://doi.org/10.1029/91JB02047
SINGH, S. K. and M. ORDAZ, 1994. Seismic Energy Release in Mexican Subduction Zone Earthquakes (accepted for publication in Bull. Seis. Soc. Am.).