Seismic Strong Motion Array Project (SSMAP) to Record Future Large Earthquakes in the Nicoya Peninsula Area, Costa Rica

E. Lafromboise¹, G. Simila1, K. McNally², and R. Quintero^3
1California State University, Northridge, CA, [email protected], [email protected]
²University of California, Santa Cruz, CA, [email protected]
³Universidad Nacional, Heredia, Costa Rica, [email protected]

Since 2006, the seismic strong motion array project (SSMAP) for the Nicoya Peninsula in northwestern Costa Rica has been composed of 13 sites including Geotech A900/A800 accelerographs (three-component), Ref-Teks (three-component velocity), and Kinemetric Episensor seismographs. The main objectives of the array are to: 1) record and locate strong subduction zone mainshocks [and foreshocks, “early aftershocks”, and preshocks] in Nicoya Peninsula, at the entrance of the Nicoya Gulf, and in the Papagayo Gulf regions of Costa Rica, and 2) record and locate any moderate to strong upper plate earthquakes triggered by a large subduction zone earthquake in the above regions. Our digital accelerograph array has been deployed as part of our ongoing research on large earthquakes in conjunction with the Earthquake and Volcano Observatory (OVSICORI) at the Universidad Nacional in Costa Rica. The countrywide seismographic network has been operating continuously since the 1980s. The recording of seismicity and strong motion data for large earthquakes along the Middle America Trench (MAT) has been a major research project priority over these years, and operation of this network spans nearly half the time of a “repeat cycle” (~50 years) for large (Ms ~7.5-7.75) earthquakes beneath the Nicoya Peninsula, with the last event in 1950. The major goal of our project is to contribute unique scientific information pertaining to a large subduction zone earthquake and its related seismic activity when the next large earthquake occurs in Nicoya. We are now collecting a database of strong motion records for moderate-sized events to document this last stage prior to the next large earthquake. We have recorded 10 events with magnitudes equal to 4.0 or greater (and accelerations of 0.2g) from the Nicoya regions of Tamarindo to Samara. The events show reverse faulting along the subduction zone.

AAPG Search and Discovery Article #90088©2009 Pacific Section Meeting, Ventura, California, May 3-5, 2009