Samoa - Ta'u island - Sentinel-2 Copernicus image from 29.10.2019 / GVP-12401 description below - one click to enlarge
The HVO reported that earthquakes were felt by residents of the Manu'a group of islands in American Samoa beginning July 26. Residents of Ofu and Olosega Islands began reporting earthquakes on August 10.
USGS scientists arrived on the islands and installed two microseismometers, one in the village of Fitişuta on Taşu Island on August 13 and the other in the village of Olosega on August 14. The instruments started recording about 20 earthquakes per hour. The largest earthquakes, including felt events, have been estimated between magnitudes 2 and 3; most events were too small to feel. The exact location and depth of these earthquakes was unknown, due to limited earthquake monitoring equipment, although data suggests the events occurred beneath the Manu'a Islands, likely closer. from the island of Ta'u.
Ta'u Island in eastern American Samoa is the exposed portion of the Lata Shield volcano, seen in this Sentinel-2 satellite image from October 29, 2019 (N is top; this image measures about 13 km across diameter). Smaller cones and craters formed on the flanks, and a major flank collapse event around 22 ka resulted in steep scarps on the south side of the island. A complex tuff-cone is partially visible at the northwest end of the island (top).
The HVO noted that volcanoes in American Samoa were monitored remotely by satellites and a remote seismic station in Apia, Samoa; the lack of ground monitoring stations does not allow advance warning of new activity. The Volcanic Alert Level and Aviation Color Code has been classified as Unassigned due to the lack of a volcano monitoring network.
Sources: HVO & Global Volcanism Program weekly report
Eruptive activity continues at Semeru, on Java.
Below the cloud cover, a few thermal anomalies, between 7 and 12 MW, are reported by Mirova.
The seismicity of August 17 is characterized by:
- 72 eruption earthquakes, with an amplitude of 10-23 mm and an earthquake duration of 55-155 seconds.
- 1 blast/emission earthquake, with an amplitude of 5 mm and an earthquake duration of 60 seconds.
- 3 distant tectonic earthquakes with an amplitude of 6-25 mm, S-P 18-134 seconds and an earthquake duration of 47-340 seconds.
The activity level remains at 3 / siaga, with the recommendation of:
1. Do not carry out any activity in the southeastern sector along Besuk Kobokan, up to 13 km from the summit (the center of the eruption). Outside of this distance, the community does not conduct activities within 500 meters of the bank (river edge) along Besuk Kobokan due to the potential for expansion from hot clouds and lava flows. at a distance of 17 km from the summit.
2. Do not travel within 5 km of the crater/summit of Mount Semeru as it is subject to the danger of rock throwing (incandescent).
3. Be aware of the potential for hot cloud avalanches (APGs), lava avalanches and lahars along the rivers/valleys that originate at the summit of Mount Semeru, especially along Besuk Kobokan, Besuk Bang, Besuk Kembar and Besuk Sat as well as potential lahars in the rivers a small river which is a tributary of Besuk Kobokan.
Sources : PVMBG& Mirova