Instituto Geofísico del Perú (IGP) reported that, during the last 12 months, seismicity at El Misti was dominated by volcano-tectonic (VT) earthquakes. Two seismic swarms (more than 100 events per day) occurred during the last three months, on 19 May and 3 June. An increase in tremor was noted in April, although the total duration did not exceed 10 minutes and was generally low-amplitude. Long-period seismicity was not significant. In the last 15 days, seismicity increased slightly and tremor was recorded daily.

Geologic Background. El Misti is a symmetrical andesitic stratovolcano with nested summit craters that towers above the city of Arequipa, Peru. The modern symmetrical cone, constructed within a small 1.5 x 2 km wide summit caldera that formed between about 13,700 and 11,300 years ago, caps older Pleistocene volcanoes that underwent caldera collapse about 50,000 years ago. A large scoria cone has grown with the 830-m-wide outer summit crater. At least 20 tephra-fall deposits and numerous pyroclastic-flow deposits have been documented during the past 50,000 years, including a pyroclastic flow that traveled 12 km to the south about 2000 years ago. The most recent activity has been dominantly pyroclastic, and strong winds have formed a parabolic dune field of volcanic ash extending up to 20 km downwind. An eruption in the 15th century affected nearby Inca inhabitants. Some reports of historical eruptions may represent increased fumarolic activity.

Source: Instituto Geofísico del Perú (IGP)