Temporal and spatial evolution of instrumented seismicity in the Trans-Mexican Volcanic Belt

摘要

For an adequate analysis of the seismic threat and, consequently, of the seismic risk of an area, it is required to have accurate and complete information about the occurrence of earthquakes in the past. These data can be divided into three classes, which correspond to stages in its time evolution: Paleoseismic, Historical and Instrumented. All of them combine to form the core of a comprehensive earthquake occurrence data set. The instrumented seismicity provides information of great relevance on the occurrence of micro and macro-seismicity that allows having a better panorama of the tectonic situation and current activity of the faults of the region of interest as well as its effects. However, if such data are used indiscriminately, due to inhomogeneity in time and space, this can result in an erroneous bias in the hazard and risk calculations. In order to use these data in a correct way, a comprehensive analysis is required so it is possible to detect artifacts caused by the operation of the network (e.g. installation, updating or removal of stations, changes in reporting and measurement procedures, etc.), which in turn affect other subsequent studies. This paper presents an analysis of instrumented seismicity data for the region of the Trans-Mexican Volcanic Belt: The interest in the seismicity of this region has been somewhat obscured by the overwhelming activity along the subduction margin. Nevertheless, catastrophic events have histdrically taken place in this region. Data from the National Seismological Service of Mexico as well as from other sources are included. The history of the report, the spatio-temporal variations in the minimum magnitude of completeness, the current resolution of the network and the resolution in pa . si decades are discussed. Other changes, which have some influence on the catalog, are also analyzed. We found that the western and eastern sectors of the Trans-Mexican Volcanic Belt have a better resolution than the central sector. Overall, appropriate M(c )values for the whole of the region are 4.6 for the period 1988-1996, 4.1 for the period 1997-2007, and 3.9 from 2008 through 2018. Nevertheless, lower identified thresholds for some of the sections can help with improved estimates of seismic risk. It is intended that with this information, the researcher is better able to interpret this data and thus use them consistently in follow-up studies.Since the pattern observed at large magnitudes remains after considering appropriate cut-offs as obtained by the methods employed here, it is a strong indication that the variations in seismicity between the eastern and western sectors of the TMVB as compared to the central sector, are a real pherimenon.