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An earthquake early warning algorithm based on the P-wave energy released in the t (sub s) -t (sub p) interval

Armando Cuellar, Gerardo Suarez and J. M. Espinosa-Aranda
An earthquake early warning algorithm based on the P-wave energy released in the t (sub s) -t (sub p) interval
Bulletin of the Seismological Society of America (February 2018) 108 (1): 238-247

Abstract

The tS-tP earthquake early warning algorithm measures the energy of the P-wave coda on the vertical component in the tS-tP period to make a magnitude threshold estimation. The algorithm is based on two parameters: the logarithm of the peak ground acceleration, max(a(tS-tP)) and the logarithmic cumulative acceleration SA(tS-tP). The model is built using a learning algorithm that iteratively parameterizes the linear fit of max(a(tS-tP)) and SA(tS-tP) to Mw in segments. Training datasets were based on 324 accelerograms from 101 earthquakes (4.8< or =Mw< or =8.1) in the Mexican subduction zone from 1985 to 2013. The algorithm is supervised to avoid outliers in the data. The process results in a family of linear equations parameterizing the observations to magnitude m(tS-tP) calibrated to the observed Mw. The algorithm was successfully tested using a dataset of 28 earthquakes in the Mexican subduction zone, from 2014 to 2017. The performance of tS-tP algorithm was tested as a warning tool using 89 earthquakes in the Mexican subduction zone from 1985 to 2017, that met the criterion of having at least two stations within 70 km from the epicenter. The results show that 79 were correctly screened. The magnitude of six events was overestimated and four were underestimated. These earthquakes had an unfavorable station distribution. The Mw 6 South Napa, California, earthquake of 24 August 2014 was used also as a test case. The two closest stations identified it as Mw> or =5.8 within 2 s after the arrival of the P phase. This resulted in a lead time of 10 s in Berkeley and 12 s in San Francisco, prior to the arrival of the S waves. Thus, the tS-tP algorithm proves to be a reliable tool for seismic early warning where hypocenters are close to the target cities.


ISSN: 0037-1106
EISSN: 1943-3573
Coden: BSSAAP
Serial Title: Bulletin of the Seismological Society of America
Serial Volume: 108
Serial Issue: 1
Title: An earthquake early warning algorithm based on the P-wave energy released in the t (sub s) -t (sub p) interval
Affiliation: Centro de Instrumentacion y Registro Sismico, Mexico City, Mexico
Pages: 238-247
Published: 201802
Text Language: English
Publisher: Seismological Society of America, Berkeley, CA, United States
References: 21
Accession Number: 2018-052108
Categories: Seismology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sketch maps
N14°30'00" - N32°43'00", W117°00'00" - W86°45'00"
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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