Chaitén bulletin no. 92 (12 May 2009)

Bulletin no. 92 on the eruption of Chaitén volcano, covering the period 5-12 May 2009, is now available as a PDF via the informes page of the Observatorio Volcanológico de los Andes del Sur (OVDAS) website. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 92
5-12 MAY 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

The DGAC camera in Chaitén shows that the eruption of the volcano has continued in unchanging form with its column of gas and ash rising occasionally to 1.5 km above the dome complex. A predominance of water vapour has been observed in the column because of atmospheric humidity and low temperatures, which has caused condensation. The block-and-ash flows have persisted, indicating that the dome complex continues to grow.

2. Seismic activity

The seismicity registered by the Chaitén volcano monitoring network continues to show a relatively stable behaviour, although it is noteworthy that the elevated seismicity has now been maintained for a period extending to almost two months. The average of HB-type [hybrid] earthquakes has remained between 11 and 16 events per day. The magnitudes have also persisted in high values, reaching up to magnitude 4.2. In relation to the seismic energy released RSAM, this has continued to show values similar to previous weeks, although it was possible to determine three high points recorded on 7 and 11 May, with values that exceeded 130,000 units (Fig. 1). Finally, with respect to the epicentres of the HB-type earthquakes of greater magnitude, these have been located on the western edge of the caldera, with depths concentrated principally between 5 and 9 km.

Fig. 1. RSAM graph showing the relative stability of seismic energy released, although on 7 and 11 May three events exceeding 130,000 units were recorded. [Click on image for enlarged version.]

3. Conclusions and interpretation

The eruptive activity continues with sustained growth of the dome complex, which has grown in height and extent, with the generation of block-and-ash flows. The seismic activity occurring during this period has remained relatively stable, although the seismic energy released RSAM shows a slight increase in the form of points on 7 and 11 May exceeding 130,000 units. In consequence, the latent danger remains 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 continues at a high level with the sustained growth of the dome complex, with the possibility of the generation of block-and-ash flows which may affect surrounding valleys, SERNAGEOMIN maintains Volcanic Red Alert.

[End of SERNAGEOMIN bulletin.]

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