Systematic Seismic Events Discrimination Methods at the Kenya National Data Centre (N090)

Abstract

Abstract The International Data Centre (IDC) routinely applies event screening or discrimination using a multi-technology approach in order to characterize events as either natural or anthropogenic. Various event discriminants are presented in literature. At the Kenya National Data Centre (KE-NDC or N090), a systematic and step-by-step procedure of SEISMIC events discrimination is applied. Results from the discriminants adopted are obtained within a short time and the discriminants are relatively easy and fast to use. The discriminants used at KE-NDC (N090) are ranked in a hierarchy based on results obtained from one discriminant being applied in subsequent dsicriminants and ease of returning results within the shortest time possible to allow for events discrimination and dissemination of results. The discriminants applied and their hierarchy at KE-NDC include:- (i) event location (epicenter/hypocenter parameters) (ii) hypocenter parameters based on events relocation using HYPOCENTER, (iii) magnitude determination, (iii) mb:Ms criteria and (iv) focal mechanism determination. Two seismic events are used as case examples to demonstrate how events discrimination is achieved based on the discriminants presented herein. The two seismic events are the 20190324 and 20200503 seismic events in the southwestern and northern Kenya respectively. The choice of these two events is based on the fact that they were strong enough to be recorded by a number of global seismic stations and their magnitudes are comparable to the 2009, 2013 and 2016 but slightly lower than the 20170903 DPRK announced tests. Based on the discriminants used and presented herein, the two seismic events were categorized as being due to natural earthquakes.