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El Salvador: Chaparrastique/San Miguel calming down? 13 July 2009

Posted by admin in activity reports, El Salvador, San Miguel.
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San Miguel from the north, 22 February 2005. Image Courtesy Servicio Nacional de Estudios Territoriales (SNET).
San Miguel from the north, 22 February 2005. Courtesy Servicio Nacional de Estudios Territoriales (SNET). [source]

El Salvador’s geological service, the Servicio Nacional de Estudios Territoriales (SNET), issued a special bulletin on 10 July reporting that the seismic activity recently observed at San Miguel volcano (known locally as Chaparrastique) was ‘showing a tendency towards decline’:

Yesterday, 9 July 2009, the microseismicity at the volcano declined to a daily average of 147 units RSAM. Today [10 July 2009], up to 15:00, the seismic stations have registered a daily average of 116 units. If this is compared to the values of previous days it can be seen that there is a tendency towards decline. It is important to note that the seismic energy of the volcano normally fluctuates between 30 and 50 units RSAM.

SNET is continuing to monitor the situation closely, and for the moment security measures, including a 2-kilometre-radius exclusion zone around the summit of the volcano, are remaining in force.

News
Sigue disminuyendo sismicidad en volcán ChaparrastiqueDiario La Página, 11 July 2009

Information
Global Volcanism Program: San Miguel – summary information for San Miguel/Chaparristique (1403-10=)
Servicio Nacional de Estudios Territoriales (SNET) – Salvadorean national geological service

The Volcanism Blog

Increased seismicity at San Miguel volcano (Chaparrastique), El Salvador 7 July 2009

Posted by admin in activity reports, El Salvador, San Miguel.
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San Miguel volcano, also known locally as Chaparrastique, is situated in the east of El Salvador and is a mere 15 km away from the city of San Miguel (population more than 200,000). It is one of El Salvador’s most active volcanoes, with a record of frequent eruptions since the early sixteenth century.

There are now reports of increased seismic activity, in the form of microquakes, at the volcano. The Salvadorean geological service, the Servicio Nacional de Estudios Territoriales (SNET), reports in a special bulletin that there has been an ‘increase in microseismicity [microsismicidad] at Chaparrastique volcano beginning at 03:00 on 6 July 2009′ which is reflected in the RSAM signal which has been fluctuating at 700-1300 units, well above the normal hourly average of 30-50 units RSAM. Such ‘microseismicity’ has been associated in the past with other manifestations of volcanic activity, and is caused by the heating of water within the volcano. The SNET bulletin explains:

The microseismicity is associated with the pressure of [water] vapour which causes the volcanic structure to vibrate, and which is caused by the heating and evaporation of rainwater which infiltrates and moves through the strata of the volcano, increasing its internal pressure.

A 2-kilometre-radius ‘security zone’ has been imposed around the volcano, with local residents and tourists being advised to keep away while monitoring of the volcano continues.

News
Reportan major actividad del volcán de San MiguelEl Diario del Hoy, 6 July 2009
Volcán sube los niveles de actividadEl Diario del Hoy, 6 July 2009
Volcán Chaparrastique de El Salvador incrementa su actividad microsísmica – Terra.com, 7 July 2009
Vigilan volcán salvadoreño por actividad microsísmica – Univisión, 7 July 2009

Information
Global Volcanism Program: San Miguel – summary information for San Miguel/Chaparristique (1403-10=)
Servicio Nacional de Estudios Territoriales (SNET) – Salvadorean national geological service

The Volcanism Blog