Macroseismic Study of the Mw 7.5 21 January 2003 Colima, Mexico, Across-Trench Earthquake

Abstract

A field investigation of residential house damage in 83 localities of the Occidental part of México allowed construction of a macroseismic map of the moment magnitude 7.5 2003 Colima earthquake. The 12-grade modified Mercalli (MM) scale and the 7-grade damage scale of Whitman (1988) were used for estimating the earthquake intensities. The macroseismic effects of this earthquake were unexpected for the Occidental part of México. The earthquake occurred within the across-trench structure of the El Gordo Graben and was characterized by the down-dip acrosstrench directivity of its rupture, as reconstructed from seismic-waveform modeling. It was a reason for the severe damage to buildings in the localities situated at distances where usual along-trench rupturing subduction earthquakes of the same magnitude do not produce any significant damage. The macroseismic map of the 2003 earthquake shows that the narrow (30 km wide) MM VII zone was elongated (up to 60 km) in the northeast direction toward the continental part of Colima state. As a result, the intensity in Colima city was 1.5 grades larger than would be expected for this magnitude according to the proposed attenuation of intensity with distance relationship for earthquakes from the Mexican subduction zone.

Comparison of macroseismic-intensity scales by considering empirical observations of structural seismic damage

“…According to the related principle of statistical analysis and probability model, vulnerability analysis of the seismic-damage observation data was performed, and the DPM model based on the empirical seismic damage was established. These (Appendices 5 to 7) show the empirical vulnerability matrices of MS, RC, and BFM based on field observations of seismic damage in Dujiangyan seismic region assessed by the EMS-98, MSK-81, and CSIS-08 intensity scales (Eleftheriadou and Karabinis, 2011; Lagomarsino and Giovinazzi, 2006; Zobin et al, 2007). Based on these field seismic vulnerability matrices, this study carried out numerical and model regression analyses of different intensity scales for structures in multiple-intensity regions.…”

“…Based on these field seismic vulnerability matrices, this study carried out numerical and model regression analyses of different intensity scales for structures in multiple-intensity regions. Figures 4 to 6 demonstrate the results of the seismic damage analyses of MS, RC, and BFM, respectively, in regions with various different intensities (Zhou et al, 2013; Zobin et al, 2007).…”

“…Davison (1921) elaborated that this scale was distinct from the original in that it included observation data at all levels and took into account actual survey data of seismic damage, particularly with regard to the seismic damage of building structures. In 1931, Harry Wood and Frank Neumann revised the MCS scale to better assess the seismic damage suffered by American buildings and compiled the 12° Modified Mercalli Intensity Scale of 1931 (MMI-1931) (Zobin et al, 2007). By considering the characteristics of seismic damage exhibited by four masonry and brick (MS) structures using GMICE (Gutenberg and Richter, 1956), Charles Richter revised the 1931 version of the modified Mercalli intensity (MMI-1931) and proposed the 1956 version of the MMI scale, namely, MMI-56 (Richter, 1958).…”

Microzonation of seismic risk in a low-rise Latin American city based on the macroseismic evaluation of the vulnerability of residential buildings: Colima city, México

“…There is no exact equivalence between masonry materials assumed in the MM scale (4 types) and the 3 masonry types in Colima. Therefore, we slightly modified the description of damage according to our experience in macroseismic studies of Mexican masonry after the 1995 and 2003 large Mexican earthquakes (Zobin and Ventura-Ramírez, 1998;Zobin and Pizano-Silva, 2007). Richter, 1958;Tiedemann, 1992 Note.…”

“…The position of Colima city is shown by a diamond. The epicenters of the 1932, 1941, and 1973 earthquakes are shown according to Pacheco and Sykes (1992), the 1995 earthquake according to Zobin and VenturaRamírez (1998) and the 2003 earthquake according to Zobin and Pizano-Silva (2007). plates along the Middle American trench. The earthquakes occurring within the Mexican subduction zone have reached magnitudes up to 8.5, and have strongly damaged the Colima houses in 1900the Colima houses in , 1932the Colima houses in , 1941the Colima houses in , and 1973.…”