Analysis and proposal of empirical magnitude scaling relationships for the seismic potential of earthquakes in Central America: its application for seismic hazard studies

Central America is a seismically active region where five tectonic plates interact (North America, Caribbean, Coco, Nazca, and South America) in a subduction zone with transform faults and near to triple points. This complex tectonic setting makes the estimation of the seismic potential (maximum magnitude) a very important task. There are a series of empirical formulas and diagrams by means of which the seismic potential of faults can be estimated from rupture earthquake geometry parameters. In this study, some of these formulas were applied to approximate the magnitude of earthquakes occurred in Central America, comparing the estimated magnitudes with those observed instrumentally. This has been accomplished based on the most complete data set of relevant and better characterized earthquakes generated by faults in the region. The data set consists in a compilation of the seismic events and its relatively well-established rupture parameters (length, width, area, slip, magnitude) and characteristics (location, faults, or possible associated faults, as well as localized aftershocks). The slip rate was incorporated, when available, but considering the current lack of information and, in some cases, the high uncertainty in its estimation, the use of other simpler rupture parameters is more practical and applicable for the region. Based on this, we identified which of the current available formulas developed worldwide, estimate magnitudes in a better way for the Central American seismotectonic context. The preliminary results show a better fit with the instrumental data, when the empirical equations were used with the segmented fault length. These outcomes were specifically validated for lengths between 10 and 30 km, in which the database presents good information coverage. We found that some empirical relationships fit quite well the observed data, including the classical Wells & Coppersmith (1994) equations. Finally, according to our data set compilation, we will try to propose a new empirical specific earthquake scaling relationship for Central America to be included in future seismic hazard studies. Is recommended, when possible, complement these approaches with more detailed historical seismicity review and paleoseismological, geodetic and neotectonic studies, to determine more precisely and realistically the fault’s maximum magnitude. Also, we suggest make estimates of the magnitude using the maximum and the segmented fault length and differentiating between ruptures at depth in the seismogenic zone (smaller) and ruptures in surface (larger). This approach is relevant due to the selection of an earthquake scaling relationships for a specific region is typically an abbreviated component of seismic-hazard analysis, being an important issue for the definition of source models which are one of the main inputs in the hazard estimation.