Servicio Nacional de Estudios Territoriales (SNET) reported on 10 October that an Alert Level for San Miguel was established as Green within 4 km from the center of the crater due to a slight increase in seismic activity. On 15 October, the Alert Level was increased to Yellow due to further increases in seismic activity, but then decreased to Green again the next day.

Geological Summary. The symmetrical cone of San Miguel, one of the most active volcanoes in El Salvador, rises from near sea level to form one of the country's most prominent landmarks. A broad, deep, crater complex that has been frequently modified by eruptions recorded since the early 16th century caps the truncated unvegetated summit, also known locally as Chaparrastique. Flanks eruptions of the basaltic-andesitic volcano have produced many lava flows, including several during the 17th-19th centuries that extended to the N, NE, and SE. The SE-flank flows are the largest and form broad, sparsely vegetated lava fields crossed by highways and a railroad skirting the base of the volcano. Flank vent locations have migrated higher on the edifice during historical time, and the most recent activity has consisted of minor ash eruptions from the summit crater.

Source: Servicio Nacional de Estudios Territoriales (SNET)