Teresito Bacolcol, Alfie Pelicano, Genesis Sapla, Zachary Albert Ragadio, Mary Lizeth Anero, Cassandra Joy Cabigan, and Alberto Baloto

Philippine Institute of Volcanology and Seismology (PHIVOLCS) PHIVOLCS Bldg. C.P. Garcia Avenue, University of the Philippines Campus, Diliman, Quezon City, 1101 Philippines

Abstract

The long-term interseismic surficial velocities and horizontal displacements within the epicentral region of the October 2019 Cotabato earthquake series (M6.4 on 16 October 2019; M6.6 on 29 October 2019; and M6.5 on 31 October 2019) were determined using Global Positioning System (GPS) data gathered from campaign surveys conducted in Cotabato province. Processing of GPS campaign data culled between 2009 and 2018 showed surficial interseismic velocities ranging from 0.7 to 67 mm/yr, with azimuths from N270° to N296°, calculated with respect to the Eurasian plate. On the other hand, a combined co-seismic displacement of 334.99 mm was derived from GPS campaigns conducted three days after the 31 October 2019 M6.5 Cotabato earthquake. The direction of the displacements of the two GPS stations closest to the epicenters indicate a largely right-lateral strike-slip motion. This calculated displacement may be cumulative coseismic displacements of the three strong successive earthquake events.

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This report to be cited as: Teresito Bacolcol, Alfie Pelicano, Genesis Sapla, Zachary Albert Ragadio, Mary Lizeth Anero, Cassandra Joy Cabigan, and Alberto Baloto. 2021. Interseismic Surficial Velocities and GPS Motions Associated with the October 2019 Cotabato Earthquake Series. PHIVOLCS Open-File Report No. 21-01, 8 pages.

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