Primary sources: earthquake.usgs.gov, earthquake.usgs.gov, scedc.caltech.edu

The U.S. Geological Survey office in Pasadena issued severe earthquake warnings for California at 10:27 a.m. PST Tuesday through the federal IPAWS system after ShakeAlert reported that an earthquake had been detected^1,2,3,4.

USGS later tied the alerts to an earthquake south of the U.S.-Mexico border, about 9 to 10 kilometers north of Delta in Baja California, Mexico, at 10:27:31 a.m. PST, with a depth of about 15.6 to 16 kilometers^5,6.

The IPAWS messages, coded EQW, listed severity as severe, urgency as immediate and certainty as observed, and told people to drop, cover and hold on¹. USGS Pasadena sent at least four matching Wireless Emergency Alerts within three seconds, from 10:27:40 a.m. to 10:27:43 a.m. PST, each set to expire after five minutes^1,2,3,4.

ShakeAlert's product page said an initial magnitude estimate of 5.2 went out 9.3 seconds after origin, a peak estimate of 5.4 at 14.4 seconds, and a final estimate of 5.0 at 28.1 seconds, and that a Wireless Emergency Alert was distributed because the peak estimate was at least 5.0. The ANSS report 133 seconds after origin listed magnitude 4.7.

USGS event key points described a magnitude 4.7 earthquake near Delta while the reviewed origin on the same page listed moment magnitude 4.9⁵. Caltech's Southern California Seismic Network listed moment magnitude 4.7, 10 kilometers north of Delta, at 15.77 kilometers depth⁶.

FOX 5 San Diego, in a report carried on AOL, said the epicenter was about 22 miles southeast of Mexicali and that shaking was reported throughout Southern California. The New York Post said some people in California and Arizona reported the shaking on USGS Did You Feel It⁷.

El Imparcial, citing Mexico's Servicio Sismologico Nacional, reported a separate magnitude 4.1 earthquake at 10:17 a.m. Baja time, 27 kilometers northwest of Guadalupe Victoria, 10 minutes before the USGS 4.7 near Delta. FOX 5 said USGS listed at least three earthquakes between magnitude 2.8 and 3.3 in the same region on Monday.

USGS assessed a low likelihood that the earthquake caused damage and identified it as a potential mainshock of a sequence⁵. FOX 5 said the governor of Baja California stated on social media that no damages had been reported. The New York Post cited USGS as putting a 66 percent chance on an aftershock of magnitude 3.0 or greater in the next week⁷. Independent confirmation of injuries was not in the sources reviewed.

Sources

1. US GEOLOGICAL SURVEY, Pasadena, CAUSGS Earthquake WarningNov 3, 1:27 PM
2. USGSM 4.9 - 9 km N of Delta, B.C., MXNov 3, 1:27 PM
3. Caltech SCSNInfo for Eq ci41572064Nov 3, 1:27 PM
4. New York PostPreliminary 4.7 magnitude earthquake shakes Southern CaliforniaNov 3, 8:06 PM
5. FOX 5 San DiegoMagnitude 4.7 earthquake shakes Baja California, felt across Southern CaliforniaNov 3, 2:16 PM

El Imparcial · USGSShowHide

1. El ImparcialRegistran dos sismos en Mexicali durante la manana de este martesNov 3, 3:00 PM
2. USGSShakeAlert product for ci41572064Nov 3, 1:27 PM

Read the original at US GEOLOGICAL SURVEY, Pasadena, CA ↗