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Chaitén bulletin no. 103 (3 August 2009) 20 August 2009

Posted by admin in activity reports, Chaitén, Chile, eruptions.
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Here’s SERNAGEOMIN bulletin no. 103 on the eruption of Chaitén volcano, dated 3 August and covering the period 23 July to 3 August 2009. The original is available as a PDF via the informes page of the Observatorio Volcanológico de los Andes del Sur (OVDAS) website. Translation as follows.

CHAITÉN VOLCANO
TECHNICAL BULLETIN NO. 103
23 JULY-3 August 2009
OVDAS-SERNAGEOMIN

1. Visual monitoring

The images observed through the DGAC camera, located in Chaitén to the south of the volcano, show that the eruption has continued in an unchanging form with its column of gas and ash which has occasionally risen to 1.5 km above the dome complex. At times it has been possible to distinguish a secondary and intermittent centre of emission to the west, very close to the principal [centre of emission]. The block-and-ash flows still persist, indicating that the dome complex continues its growth, particularly towards the western sector of the caldera.

2. Seismic activity

The Chaitén volcano seismological monitoring network has registered an average of 31 HB-type earthquakes per day, with maximum magnitudes reaching 4.4; the increase in occurrence of seismic events of magnitudes greater than 3.0 has been notable, with a daily average of 17. The majority of the seismicity displays very similar wave forms, which suggests that they originate in the same source and are caused by the same mechanism of origin. Comparing the seismicity of this period to that of previous weeks, the energy released RSAM has not exceeded 150000 units.

3. Conclusions and interpretation

The eruptive activity continues with the growth of the dome complex, only observable on some occasions because of the bad weather, continues, as does the 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. The seismicity in this period has remained constant when compared with the preceding week, both in numbers of earthquakes and their magnitude. Moreover, the quantity of pyroclastic material from fallen volcanic rock originating from both block-and-ash flows and lateral explosions has formed important accumulations in the adjacent valleys and especially towards the valley of the Chaitén river, from which the fresh occurrence of lahars towards Chaitén during torrential rains cannot be ruled out. In consequence, given that the seismic activity remains elevated as a result of the growth of the dome complex, with the possibility of the generation of block-and-ash flows which may affect the surrounding valleys including the new generation of new lahars, SERNAGEOMIN maintains Volcanic Red Alert.

OVDAS-SERNAGEOMIN
03.08.09

[End of another formulaic, uninformative and very tardy 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

The Volcanism Blog