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A fast earthquake early warning algorithm based on the first 3 s of the P-wave coda

Armando Cuellar, Gerardo Suarez and J. M. Espinosa-Aranda
A fast earthquake early warning algorithm based on the first 3 s of the P-wave coda
Bulletin of the Seismological Society of America (August 2018) 108 (4): 2068-2079

Abstract

A new seismic early warning algorithm is presented that estimates a magnitude threshold using the first 3 s of the P-wave coda on the vertical component. The algorithm considerably reduces the processing time compared to previous algorithms used by the Mexican seismic early warning system (Seismic Alert System of Mexico [SASMEX]). It was designed to alert earthquakes within the subducted Cocos plate. The tP+3 algorithm was based on a training dataset of 76 accelerograms of 25 Mexican in-slab earthquakes, with focal depths >40 km. The algorithm uses two parameters based on the unfiltered vertical component of the P waves: the sum of the cumulative quadratic acceleration, av(T) and theta P a parameter that represents the slope of the cumulative acceleration. The model is based on a learning machine that linearizes piecewise the empirical relation between these two parameters and magnitude Mw. The resulting algorithm was tested on nine earthquakes that took place from 2014 to 2017, recorded in 37 strong-motion records. In addition, the algorithm was evaluated in the context of the Mexican earthquake early warning, applying it to 24 in-slab earthquakes occurring from 1995 to 2017 (5.0<Mw<7.1). The magnitude of 19 earthquakes was properly estimated; for four of them, it was overestimated and in one case the magnitude was underestimated. Three earthquakes Mw>6.5 that affected Mexico City were included in the dataset: the Mw 6.5 event on 11 December 2011 and the destructive in-slab Tehuacan and Morelos earthquakes on 15 June 1999 (Mw 7.0) and 19 September 2017 (Mw 7.1). The retrospective application of the tP+3 algorithm shows that these three earthquakes are correctly identified as Mw>6 and would activate a seismic alert. The tP+3 algorithm would have given an advance warning of 34, 35, and 16 s respectively, before the arrival of strong motion in Mexico City.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 108
Serial Issue: 4
Title: A fast earthquake early warning algorithm based on the first 3 s of the P-wave coda
Affiliation: Centro de Instrumentacion y Registro Sismico, Mexico City, Mexico
Pages: 2068-2079
Published: 201808
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 17
Accession Number: 2018-081745
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N15°00'00" - N19°00'00", W102°00'00" - W97°00'00"
Secondary Affiliation: Universidad Nacional Autonoma de Mexico, MEX, Mexico
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute. Abstract, Copyright, Seismological Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 2018
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