Rapid Moment Magnitude (Mwp) Calculation for UK Broadband Seismic Stations Using Teleseismic Waves

Abstract

Determining the magnitude of an earthquake rapidly and correctly is essential to starting simulations to evaluate the potential for tsunami generation and early warning for tsunami-prone countries and rapid response, considering countries that lie in seismically active regions. Although the UK does not have a high degree of tsunami hazard, the UK seismic network can estimate the moment magnitude for large earthquakes which will occur around the globe. This study aimed to test the UK Seismological Network Broadband Seismic Stations to calculate the P-wave moment magnitude (M_wp) using teleseismic waves. The standard way to calculate the M_wp is using the P-wave portion of a seismic wave recorded at different epicentral distances. We selected twenty-five seismic events with a magnitude greater than 6.5M_w and epicentral distances between 17 and 90 degrees. The main issue is selecting the P-wave portion of a seismic wave and using a trial P-wave velocity to estimate the M_wp. We simplified the selection of a P-wave portion of seismic waves using a theoretical formula that works with epicentral distance, P-wave arrival time and an apparent P-wave velocity, which calculates the S-wave arrival time. The results show the variation between the Harvard centroid moment tensor (CMT—M_w) and M_wp, which is about ± 0.1 magnitude units in most events and ± 0.2 for some events. These results prove the M_wp technique can be applied to the UK broadband seismic network broadband seismic stations and encourage the use of it immediately following a destructive earthquake anywhere in the world.