Overview
- Mexico’s seismic service logged three magnitude 4.0 events before dawn on Oct. 21 in Baja California (northwest of San Felipe), Guerrero (south of Atoyac de Álvarez) and Michoacán (northwest of La Mira).
- A multi‑day sequence that began Oct. 19 in Oaxaca and reached Guerrero on Oct. 20 with tremors around 4.1–4.2 continues without reported impacts, according to civil protection authorities.
- Peru recorded a magnitude 4.8 near Uchiza in San Martín at 00:24 with intensity III–IV and a magnitude 4.0 offshore Chimbote in Áncash in the afternoon; the IGP reported no casualties or damage.
- Argentina’s INPRES and Chile’s CSN reported a deep quake near the Mendoza–San Juan/Valparaíso area around 11:08, measured at M4.7 by INPRES and M5.0 by CSN, felt on both sides of the Andes without reported damages.
- Mexico City’s SASMEX did not activate because recent quakes did not meet magnitude–distance thresholds, and regional agencies reiterated preparedness guidance, including building‑code compliance.