Chaitén bulletin no. 96 (8 June 2009) 10 June 2009

Bulletin no. 96 on the eruption of Chaitén volcano, covering the period 2-8 June 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 (combined with a report on Llaima) on the SERNAGEOMIN website. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 96
2-8 JUNE 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

Personnel of the Observatorio Volcanológico de Los Andes del Sur (OVDAS-SERNAGEOMIN) in the area have been able to observe that the volcanic activity continues, shown by the column of gas, water vapour and ash, which on occasion reaches a height of 1.5 km above the dome complex (Fig. 1a). From the northern sector, near a portable seismological station, continuing block-and-ash flows have been seen, indicating that the dome complex continues to grow, mainly towards the western sector of the caldera, although the major fumarolic and ash emission activity is currently exclusively in its central portion (Fig. 1b). Ashfall has been detected particularly towards the Santa Bárbara area, and occasionally on the town of Chaitén.

Figure 1a. View of the column of gas and ash from Chaitén.

Figure 1b. Detail of the domes and block-and-ash flows, principally in the western sector.

2. Seismic activity

The seismicity registered by the Chaitén volcano monitoring network has shown a slight tendency towards greater seismic activity, with an average of 15 events per day and maximum magnitudes of 4.4. Additionally, there has been a growth in seismicity of under [magnitude] 2.5, which has climbed to an average of 8-12,with a slight reduction during the last few days. The greater part of the seismicity consists of very similar wave forms, suggesting that it originates from the same source, particularly for the smaller earthquakes. When the seismicity of greater magnitude is evaluated, the events are shown to have increased slightly in number and amplitude, indicating a higher level of energy than in previous days. With regard to the seismic energy released RSAM, this has not exceeded 150,000 units.

3. Conclusions and interpretation

The eruptive activity continues with the sustained growth of the dome complex, which is rising and expanding, with the generation of block-and-ash flows (in different areas), sometimes perceptible from Chaitén. In general, the seismic activity during this period has increased. There is a continuing latent danger of collapse because of the growth of the domes, with 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 as an effect of the growth of the dome complex, with the possibility of the generation of block-and-ash flows in random directions that may affect surrounding valleys, SERNAGEOMIN maintains Volcanic Red Alert.

OVDAS-SERNAGEOMIN
08.06.09

[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

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

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

Chaitén bulletin no. 93 (19 May 2009) 5 June 2009

Bulletin no. 93 on the eruption of Chaitén volcano, covering the period 12-19 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. The elevated level of seismicity at Chaitén, now sustained for nearly two months, remains the most notable characteristic. Translation as follows.

ERUPTION OF CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 93
12-19 MAY 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

Some photographs from the DGAC camera at Chaitén show that the eruption of the volcano continues in an unchanging form, with its column of gas and ash of white to grey colouring climbing up to 1.5 km above the dome complex. Although observations have not been possible during all this period because of the adverse weather conditions, there has been a notable predominance of water vapour in the column because of the atmospheric humidity and the low temperatures, which have caused condensation. The block-and-ash flows have persisted, indicating that the dome complex has continued to grow, especially towards the south-western area of the caldera.

2. Seismic activity

The seismicity registered by the monitoring network of Chaitén volcano shows stable behaviour, although it should be emphasized that an elevated level of seismic activity has been maintained for a duration of nearly two months. The average of HB-type [hybrid] earthquakes has remained between 9 and 14 events per day, with magnitudes reaching 4.1 in some cases. With regard to the seismic energy released RSAM, this has continued to show values similar to the preceding weeks, with values that exceed 130,000 units. Moreover, it is important to note that there has been at least two groups of earthquakes originating from different sources, although [all] associated with the activity of the volcano. This has been shown by their distinct forms and the different arrival times at the [seismic] stations. The epicentres of the HB-type earthquakes of greater magnitude are located on the western edge of the caldera, with depths principally concentrated between 5 and 9 km.

3. Conclusions and interpretation

The eruptive activity continues with the sustained growth of the dome complex, which continues to rise and expand, and the generation of block-and-ash flows, which are on occasion visible from Chaitén [town]. The seismic activity occurring during the period has remained relatively stable and some of the earthquakes of greater magnitude have been slightly perceptible to people in the area. There is a continuing danger of gravitational collapses, possible explosions and the generation of block-and-ash flows, which could affect the valleys adjacent to Chaitén volcano. In consequence, given that the eruption continues, and the seismic activity associated with the sustained growth of the dome complex remains elevated, with the possibility of the generation of block-and-ash flows which may affect surrounding valleys, SERNAGEOMIN maintains Volcanic Red Alert.

OVDAS-SERNAGEOMIN
19.05.09

[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

Chaitén bulletin no. 92 (12 May 2009) 15 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