Development of an Interpolation Scheme for Seismic Indexes in Lima Metropolitan, Peru

Abstract

In recent years, the development of seismic networks in Metropolitan Lima, administrated by public and private institutions, has received special attention since it makes possible the quantification of different seismic indexes under the occurrence of earthquakes. Therefore, the integration of the information both from acceleration sensors and site conditions from microzoning studies allows the estimation of the possible extent of the damage in quasi-real time. In this study, the implementation of a system to evaluate seismic parameters in a uniform grid of 250 x 250 m2 resolution is reported. In this regard, peak ground acceleration (PGA) values from the available time-history records are computed and reduced to the engineering bedrock level. Then, by means of the interpolation technique called Ordinary Kriging, in which each seismic station is considered as a random variable and the correlation between a pair of such random variables depends only on the distance between their coordinates, the acceleration distribution is evaluated. Amplification factors are applied in order to finally bring the PGA up to the surface level. A quantitative evaluation of the accuracy of our results is performed using two recent earthquakes with moment magnitude larger than 5:  the 2019 Mw 8.0 Lagunas earthquake and 2021 Mw 6.0 Mala earthquake. The results have reproduced to some extent the seismic response of the diverse geomorphological deposits in Metropolitan Lima and suggest the inclusion of a larger number of strong motion stations in order to reduce the estimation errors.