The Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG) reported increased seismicity at Lokon-Empung. During 1 August-1 September white steam-and-gas plumes rose as high as 10 m above the vent and seismicity was dominated by shallow volcanic earthquakes occurring at a rate of 1-37 per day. Seismicity increased during 0000-0600 on 2 September and was characterized by 35 shallow volcanic earthquakes, 25 earthquakes indicating emissions, and four deep volcanic earthquakes. Seismicity continued to intensify, and by 0221 on 3 September the seismic network had recorded a total of 143 shallow volcanic earthquakes, 72 earthquakes indicating emissions, and 15 deep volcanic earthquakes. Tiltmeter data indicated inflation during 17 August-2 September. No surficial changes were observed. The Alert Level was raised to 3 (on a scale of 1-4) at 1200 on 3 September and the public was warned to stay 2.5 km away from the crater.

Geological Summary. The Lokong-Empung volcanic complex, rising above the plain of Tondano in North Sulawesi, includes four peaks and an active crater. Lokon, the highest peak, has a flat craterless top. The morphologically younger Empung cone 2 km NE has a 400-m-wide, 150-m-deep crater that erupted last in the 18th century. A ridge extending 3 km WNW from Lokon includes the Tatawiran and Tetempangan peaks. All eruptions since 1829 have originated from Tompaluan, a 150 x 250 m crater in the saddle between Lokon and Empung. These eruptions have primarily produced small-to-moderate ash plumes that sometimes damaged croplands and houses, but lava-dome growth and pyroclastic flows have also occurred.

Source: Pusat Vulkanologi dan Mitigasi Bencana Geologi (PVMBG, also known as CVGHM)