Overview

• Mexico’s National Seismological Service (SSN) logged a magnitude 4.7 quake at 00:35 local time on August 21, with an epicenter 31 km southwest of Río Grande, Oaxaca.
• Two additional tremors were recorded shortly after: magnitude 4.1 at 01:51 southwest of Río Grande and magnitude 4.1 at 03:37 west of Tapachula, Chiapas.
• Authorities reported no injuries or material damage from the latest events, and the seismic alert was not activated.
• The sequence follows a magnitude 4.3 quake near Río Grande early on August 20 that also did not trigger the alert, and 21 smaller quakes (magnitudes 1.8–3.9) recorded on August 18.
• SASMEX activates sirens only when combined distance and magnitude thresholds are met, and Protección Civil reiterated standard safety measures for felt shaking.