The Building Research Institute (BRI) opened a new website for the
strong motion observation. The website provides information related to
strong motion observation for buildings and the database containing
thousands of records obtained in the BRI strong motion network.
The URL of the website is http://smo.kenken.go.jp/

Toshihide KASHIMA
Research Engineer, IISEE

On Thursday January 8, 2009 a strong earthquake shook the northern Central
Valley of Costa Rica, 40 km north of the capital city, San Jose. The
earthquake had a magnitude Mw 6.2, a depth of 4.6 km, a maximum intensity of
IX at the mesoseismic area and is associated with a local fault named
Angel-Varablanca -NW direction SE-, located on the eastern flank of Poas
volcano. The present activity started on January 7, 2009, with a precursor
event of magnitude 4.6 Ml, which occurred in the same area. The activity was
followed by many aftershocks for more than three weeks and more than 1600
events of magnitudes greater than 2.5 Ml. Serious damage was reported on
local roads, mainly at the area between Cinchona and Varablanca, due to
landslides. Homes and some buildings at this rural area had severe damage
and generated alarm in the population at the central part of the country. 25
people died and 17 people are missing. Two hydroelectric plants in operation
of Instituto Costarricense de Electricidad (ICE) located in the area (PH
Toro II and PH Cariblanco) were partially affected. Electricity service
suffered serious breakdowns in the area of the epicenter and in the
metropolitan area was halted for an hour. Telephone services are also
saturated by at least two hours. Historically, the northern part of the
Central Valley, had been affected by several important earthquakes, as were
those that occurred in 1851 (M 6.0), 1888 (M 6.0), 1911 (M 6.1), 1912 (M
6.1) and 1955 (M 5.8), all of them related to local faults. The latest
seismic activity before the earthquake of January 8, 2009 was a seismic
swarm in the same area on June and July 2005, related to the
Angel-Varablanca fault, a fault previously known and described.

Rafael Barquero P. (1987-88S, Costa Rica)

This report and other reference materials on the Cinchona Earthquake are
available on IISEE website.
http://iisee.kenken.go.jp/special/20090108costarica.html

IISEE