Application of Regional Moment Tensor (RMT) inversion procedures using regional seismograms from the Puerto Rico seismic network

Abstract

We present the results of the application of regional moment tensor (RMT) inversion procedure within the eastern Caribbean area using regional seismograms recorded by the Puerto Rico Seismic Network (PRSN) during 2003-2006. Using data recorded over a three-year period, we estimated the source mechanisms for 6 earthquakes within the eastern Caribbean with moment magnitudes (Mw) ranging from 4.5 to 6.5. Comparisons of the computed source parameters with international agencies indicate that the RMT procedure provides an accurate estimate of the moment magnitude. The analysis is based on the moment-tensor inversion methodology developed by Randall et al., (1995) as implemented by Mendoza (2005) to estimate the earthquake source mechanism and magnitude from seismic waveforms recorded at regional distances. This study evaluates variables, such as the velocity model and the signal-to-noise-ratio (SNR) of the recorded waveforms, and it evaluates two different bandpass filters with corner frequencies at 20- to 50- sec and 30- to 60- sec. Two velocity models were tested, the regional Caribbean model from Ewing et al., (1968) and the Preliminary Reference Earth Model (PREM) from Dziewonski and Anderson, (1981). Our results show that using the combination of the PREM velocity model with a 30- to 60- sec bandpass filter with multiple stations improves the root-mean-square (RMS) error between the synthetics and observed waveforms. Single PRSN station inversions produce large RMS errors except at stations SJG and MPR. We observed that by changing the event depth and repeating the RMT inversion we were not able to constrain the depth of the event.