Seismicity was recorded at the volcano during March-May by a telemetered seismic station (VNV) 4.5 km from the summit, at 1,400 m elev. The average tremor frequency decreased slightly from 1.9 Hz (in March-April) to 1.8 Hz (in May). Tremor frequency also decreased with distance from the summit. Average frequencies of 1.9, 0.8, and 0.6 Hz were recorded 4.5 km (station VNV), 18.7 km (station PP) and 21 km (station PL) from the volcano, respectively, in April. Since 28 May, activity has increased, and both tremor and volcanic earthquakes have been recorded.

Geological Summary. The glacier-covered Villarrica stratovolcano, in the northern Lakes District of central Chile, is ~15 km south of the city of Pucon. A 2-km-wide caldera that formed about 3,500 years ago is located at the base of the presently active, dominantly basaltic to basaltic-andesite cone at the NW margin of a 6-km-wide Pleistocene caldera. More than 30 scoria cones and fissure vents are present on the flanks. Plinian eruptions and pyroclastic flows that have extended up to 20 km from the volcano were produced during the Holocene. Lava flows up to 18 km long have issued from summit and flank vents. Eruptions documented since 1558 CE have consisted largely of mild-to-moderate explosive activity with occasional lava effusion. Glaciers cover 40 km2 of the volcano, and lahars have damaged towns on its flanks.

Information Contacts: G. Fuentealba and P. Peña, Univ de La Frontera; M. Petit-Breuilh, Fundación Andes, Temuco.