Performance of the Seismic Alert System of Mexico During the 23 June 2020, Oaxaca Earthquake (Mw 7.4)
Session: Earthquake Early Warning System in the Americas: The On-Going Effort and the State of the Art II
Type: Oral
Date: 4/20/2021
Presentation Time: 09:45 AM Pacific
Description:
The Mexican Seismic Alerting System (SASMEX) successfully detected and screened the 23 June 2020 earthquake (Mw7.4) in southern Mexico. The alert was activated simultaneously in seven cities. The time between the alert broadcast and the initiation of strong shaking ranged from 30 s in the city of Oaxaca and 134 s in Mexico City. Here, we dissect SASMEX messages from the time the earthquake was detected to the generation of maps of peak ground acceleration in Mexico City. Based on the tS-tP algorithm, the first magnitude estimation (Mw ≥ 6.5) was from a station located 3 km away from the epicenter. On this basis, a pre-alert message was issued. Confirmation of the magnitude came from an adjacent station located 43 km from the epicenter. The same algorithm confirmed the magnitude threshold and triggered the general alert 16 s after the origin time. In this case, the decision to broadcast the alert took longer than in previous large earthquakes. This was due to the relatively large interstation spacing in this region. An algorithm called tP + 3, that estimates magnitude based on the first three seconds after the onset of the P wave, would have issued the alert 4 s before. However, the triggering procedures in place today require that the same algorithm is used to issue the alert. SASMEX warned all cities where it operates with ample time. Also, the earthquake of 23 June 2020 provided important lessons to further improve the performance of SASMEX. Peak ground acceleration in key sites in Mexico City was estimated 3.5 minutes after the origin time of the earthquake and one minute after strong shaking began, allowing authorities to take the appropriate measures.
Presenting Author: Gerardo Suarez
Student Presenter: No
Authors
Gerardo Suarez Presenting Author Corresponding Author gersua@yahoo.com Instituto de Geofísica, UNAM |
J.M. Espinosa-Aranda maranda@unam.mx CIRES |
Armado Cuellar a.cuellar@cires-ac.mx CIRES |
Antonio Uribe a.uribe@cires-ac.mx CIRES |
Gerardo Ibarrola g.ibarrola@cires-ac.mx CIRES |
Armando García a.garcia@cires-ac.mx CIRES |
Roberto Islas r.islas@cires-ac.mx CIRES |
Lucio Camarillo l.camarillo@cires-ac.mx CIRES |
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Performance of the Seismic Alert System of Mexico During the 23 June 2020, Oaxaca Earthquake (Mw 7.4)
Category
Earthquake Early Warning System in the Americas: The On-going Effort and the State of the Art