Report on Turrialba (Costa Rica) — March 2000
Bulletin of the Global Volcanism Network, vol. 25, no. 3 (March 2000)
Managing Editor: Richard Wunderman.
Turrialba (Costa Rica) Microseisms diminish in number during July-November 1999
Please cite this report as:
Global Volcanism Program, 2000. Report on Turrialba (Costa Rica) (Wunderman, R., ed.). Bulletin of the Global Volcanism Network, 25:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200003-345070.
10.025°N, 83.767°W; summit elev. 3340 m
All times are local (unless otherwise noted)
Mass wasting and elevated seismicity continued at Turrialba during July-November 1999 (table 4). The seismicity has appeared anomalously high since it increased suddenly during May 1996, escalating to 540 such events in September 1996. Microseisms have dropped since then, although they still remained at over 100 per month during September and October 1999. Between April and August 1999 scientists made surveys of the distance to a reflector 500 m from the active crater on the SW flank; these failed to show significant changes in length. After 18 September three new seismic receivers helped detect and locate three earthquakes, M 1.7-2.8, at depths of 3-11 km centered 2.5-10 km E, SE, and SW of the volcano.
|Month||Total earthquakes||Microseisms||Type-AB earthquakes||Tremor duration||Max fumarolic temp.|
|Oct 1999||209||120||39||9 minutes||90°C|
|Nov 1999||144||39||42||35 minutes||90°C|
Geologic Background. Turrialba, the easternmost of Costa Rica's Holocene volcanoes, is a large vegetated basaltic-to-dacitic stratovolcano located across a broad saddle NE of Irazú volcano overlooking the city of Cartago. The massive edifice covers an area of 500 km2. Three well-defined craters occur at the upper SW end of a broad 800 x 2200 m summit depression that is breached to the NE. Most activity originated from the summit vent complex, but two pyroclastic cones are located on the SW flank. Five major explosive eruptions have occurred during the past 3500 years. A series of explosive eruptions during the 19th century were sometimes accompanied by pyroclastic flows. Fumarolic activity continues at the central and SW summit craters.
Information Contacts: E. Fernandez, E. Duarte, V. Barboza, R. Sáenz, E. Malavassi, R. Van der Laat, T. Marino, J. Barquero, and E. Hernández, Observatorio Vulcanologico y Sismologico de Costa Rica, Universidad Nacional (OVSICORI-UNA), Apartado 86-3000, Heredia, Costa Rica.