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Chaitén bulletin no. 94 (27 May 2009) 5 June 2009

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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Bulletin no. 94 on the eruption of Chaitén volcano, covering the period 20-27 May 2009, is now available as a PDF via the informes page of the Observatorio Volcanológico de los Andes del Sur (OVDAS) website. There is also a summary version on the SERNAGEOMIN website. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 94
20-27 MAY 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

Some photographs from the DGAC camera at Chaitén (located to the south of the volcano), show that the eruption of the volcano continues in unchanging form with its column of gas and ash, which occasionally climbs to 1.5 km over the dome complex. Although it has not been possible to make observations all this time because of adverse weather conditions, a predominance of water vapour in the column has been observed. Moreover, the block-and-ash flows have persisted, indicating that the dome complex continues to grow, especially towards the western sector of the caldera.

2. Seismic activity

The seismicity registered by the Chaitén volcano monitoring network shows a stable behaviour very similar to that of the preceding weeks, characterized by elevated seismic activity, with a presence of HB-type [hybrid] earthquakes of up to 18 per day and maximum magnitudes of 4.3 in some cases. In relation to the seismic energy released RSAM, this shows values similar to those reported in the preceding bulletin, with data at points exceeding 130,000 units. The epicentres of the HB-type earthquakes of greater magnitude are located on the western edge of the caldera, with depths that are concentrated principally between 5 and 9 km.

3. Conclusions and interpretation

The eruptive activity continues with sustained growth of the dome complex, observable on some occasions, which continues to rise and expand, with the generation of block-and-ash flows, visually perceptible from Chaitén [town] at some moments. The seismic activity occurring during this period has been maintained, both in average number and in magnitude. There is a continuing danger of collapse, possible explosions and generation of block-and-ash flows, which may affect the valleys adjacent to Chaitén volcano. In consequence, given that the seismic activity remains elevated and associated with the sustained growth of the dome complex, with the possibility of the generation of block-and-ash flows that may affect surrounding valleys, SERNAGEOMIN maintains Volcanic Red Alert.

OVDAS-SERNAGEOMIN
28.05.09

[End of SERNAGEOMIN bulletin.]

I am late posting this bulletin because of my absence from the blog during late May. Apologies for the delay.

For all our Chaitén coverage: Chaitén « The Volcanism Blog.

Information
Global Volcanism Program: Chaitén – summary information for Chaitén (1508-41)
SERNAGEOMIN – Servicio Nacional de Geología y Minería (Spanish)
Erupción del Volcán Chaitén – extensive coverage of the Chaitén eruption

The Volcanism Blog