Arroyo, Ivonne G.

Linkimer, Lepolt

Lücke, Oscar H.

Montero Pohly, Walter K.

English

OceanRep

CONTROL ID: 1799571TITLE: Upper-Plate Earthquake Swarms Remotely Triggered by the 2012 Mw-7.6 NicoyaEarthquake, Costa Rica.AUTHORS (FIRST NAME, LAST NAME): Lepolt Linkimer1, Ivonne G Arroyo2, Walter KMontero Pohly3, Oscar H. Lücke1INSTITUTIONS (ALL): 1. Escuela Centroamericana de Geología, Universidad de Costa Rica,San José, Costa Rica.2. Marine Geodynamics, GEOMAR Helmholtz Zentrum für Ozeanforschung, Kiel, Germany.3. Centro de Investigaciones en Ciencias Geológicas, Universidad de Costa Rica, San José, CostaRica.ABSTRACT BODY: Remotely triggered seismicity that takes place at distances greater than 1–2fault lengths appears to be a frequent phenomenon after large earthquakes, including damagingupper-plate 5.0-to-6.0 magnitude earthquakes in Costa Rica after the large (Mw greater than 7.0)inter-plate earthquakes in 1941, 1950, 1983, 1990, and 1991. On 5 of September 2012, aninter-plate 7.6-Mw earthquake struck the Nicoya Peninsula, triggering upper-plate seismicity in theinterior of Costa Rica again. The number of upper plate-earthquakes outside the Nicoya sourceregion that were recorded by the National Seismological Network (RSN: UCR-ICE) for thesix-month period after the Nicoya event was two times higher than that number of upper plate-earthquakes during the six months before it happened. We analyze the three largest upper-plateearthquake swarms that took place during the first six months after the Nicoya event. We relocatethe epicenters using a double difference algorithm with a 1D velocity model (HypoDD) and using aprobabilistic method with a 3D velocity model (NonLinLoc). Additionally we compute first motionfocal mechanisms for the largest events. The three swarms analyzed occurred at distances of 170to 350 km from the Nicoya source region in three different tectonic settings: the Cartago area inthe central part of Costa Rica near the active volcanic arc (approximately 170 km from the sourceregion), the Calero Island near the Costa Rica-Nicaragua border in the backarc Caribbean region(approximately 220 km), and the San Vito area in the Costa Rica-Panama border region, at thesouthern flank of the Talamanca Cordillera, an inactive portion of the magmatic arc(approximately 300 km). The Cartago swarm with 95 1.8-to-4.1 Mw earthquakes occurred fromSeptember 5 to October 31, 2012. The location and left-lateral solution of the largest event suggestthat the Aguacaliente fault, which caused the deadliest earthquake in Costa Rican history on May4, 1910 (Ms 6.4), is the source of some of this triggered seismicity. Moreover, seismicity patternssuggest activity on the Navarro, Queveri, Rio Macho, and Ochomogo Faults. The Calero swarmwith 70 2.5-to-4.2 Mw earthquakes took place from September 22 to October 2, 2012. Theearthquake pattern suggests a possible extension of the Hess Escarpment inland. The San Vitoearthquake swarm with 21 2.3-to-4.5 Mw earthquakes occurred between October 14, 2012 andJanuary 28, 2013. These earthquakes occurred mainly in the region between the North-Southoriented San Vito and Sereno-Alturas Faults, which are located along the inland projection of thePanama Fracture Zone. Documenting remotely triggered earthquakes may provide us with insightsinto the physics of the earthquake cycle, and may greatly improve seismic hazards assessment byilluminating active structures within the interior of Costa Rica and by pointing to where the nextupper-plate earthquakes might be located.KEYWORDS: 7200 SEISMOLOGY, 8100 TECTONOPHYSICS, 8170 TECTONOPHYSICSSubduction zone processes, 7230 SEISMOLOGY Seismicity and tectonics.(No Image Selected)(No Table Selected)http://agu-fm13.abstractcentral.com/s1agxt/com.scholarone.s1agxt.s1agx...1 of 2 10.10.2013 12:17Additional DetailsPreviously Presented Material: 60% presented at 2013 AGU Meeting of the Americas CancunMay 2013.Contact DetailsCONTACT (NAME ONLY): Lepolt LinkimerCONTACT (E-MAIL ONLY): linkimer@email.arizona.eduTITLE OF TEAM:http://agu-fm13.abstractcentral.com/s1agxt/com.scholarone.s1agxt.s1agx...2 of 2 10.10.2013 12:17

Upper-Plate Earthquake Swarms Remotely Triggered by the 2012 Mw-7.6 Nicoya Earthquake, Costa Rica

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