The Mw 6.4 Damas, Costa Rica, Earthquake of 20 November 2004: Aftershocks and Slip Distribution

Pacheco, Jesús; Quintero, Ronnie; Vega, Floribeth; Segura, Juan; Jimenez, W.; González, Víctor

doi:10.1785/0120050261

Cited by 13 publications

(24 citation statements)

References 29 publications

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“…2002), Q: 1999 M w 6.9 Quepos (location from Universidad Nacional de Costa Rica) and O: 2002 M w 6.4 Osa (preliminary location from Jacó and RSN networks combined). Orange star: upper‐plate, 2004 M w 6.4 Damas earthquake (Pacheco et al . 2006).…”

Section: Introductionmentioning

confidence: 99%

Three-dimensionalP-wave velocity structure on the shallow part of the Central Costa Rican Pacific margin from local earthquake tomography using off- and onshore networks

Arroyo¹,

Husen²,

Flueh³

et al. 2009

Geophysical Journal International

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S U M M A R YThe Central Costa Rican Pacific margin is characterized by a high-seismicity rate, coincident with the subduction of rough-relief ocean floor and has generated earthquakes with magnitude up to seven in the past. We inverted selected P-wave traveltimes from earthquakes recorded by a combined on-and offshore seismological array deployed during 6 months in the area, simultaneously determining hypocentres and the 3-D tomographic velocity structure on the shallow part of the subduction zone (<70 km). The results reflect the complexity associated to subduction of ocean-floor morphology and the transition from normal to thickened subducting oceanic crust. The subducting slab is imaged as a high-velocity perturbation with a band of low velocities (LVB) on top encompassing the intraslab seismicity deeper than ∼30 km. The LVB is locally thickened by the presence of at least two subducted seamounts beneath the margin wedge. There is a general eastward widening of the LVB over a relatively short distance, closely coinciding with the onset of an inverted forearc basin onshore and the appearance of an aseismic low-velocity anomaly beneath the inner forearc. The latter coincides spatially with an area of the subaerial forearc where differential uplift of blocks has been described, suggesting tectonic underplating of eroded material against the base of the upper plate crust. Alternatively, the low velocities could be induced by an accumulation of upward migrating fluids. Other observed velocity perturbations are attributed to several processes taking place at different depths, such as slab hydration through outer rise faulting, tectonic erosion and slab dehydration.

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Section: Introductionmentioning

confidence: 99%

Three-dimensionalP-wave velocity structure on the shallow part of the Central Costa Rican Pacific margin from local earthquake tomography using off- and onshore networks

Arroyo¹,

Husen²,

Flueh³

et al. 2009

Geophysical Journal International

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“…Where deformation is localized, such as the M w = 6.4 Damas event, the strain is likewise in agreement with our results. For the Damas event Pacheco et al [2006] find a WSW–ENE trending shallow T axis. The change in the trajectory of d 1 in the Cordillera de Talamanca suggests that ridge collision is contributing to the contemporary motion of a fore‐arc sliver.…”

Section: Discussionmentioning

confidence: 85%

“…The focus of this paper is the western boundary of the Panama microplate, a diffuse zone of active deformation that traverses the densely populated area of Costa Rica's capital city of San Jose. This boundary has been referred to by Marshall et al [2000] as the Central Costa Rica Deformed Belt (CCRDB), and is the site of numerous damaging upper crustal earthquakes [e.g., Pacheco et al , 2006] (Figure 1).…”

Section: Introductionmentioning

confidence: 99%

“…CA, Cordillera de Aguacate; CVC, Cordillera Volcánica Central; CT, Cordillera de Talamanca; CR, Cocos Ridge; QP, Quepos Plateau. Black focal mechanisms are upper plate events, the largest one from Pacheco et al [2006], the other two from the Harvard CMT catalog. Gray focal mechanism is an interplate event taken from the Harvard CMT catalog.…”

Section: Introductionmentioning

confidence: 99%

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Collision versus sliver transport in the hanging wall at the Middle America subduction zone: Constraints from background seismicity in central Costa Rica

Lewis

Boozer²,

López³

et al. 2008

Geochem Geophys Geosyst

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[1] Earthquake focal mechanism solutions for 135 small-magnitude events are inverted for best fitting partial strain rate tensors that characterize contemporary strain in five areas that span the western margin of the Panama microplate in central Costa Rica. The results indicate the predominance of subhorizontal maximum stretching subparallel to the Middle America Trench (MAT) and provide constraints on the role of Cocos ridge collision at the MAT. The trajectory of maximum stretching changes $25°-45°over several tens of kilometers from the Central Costa Rica Deformed Belt (CCRDB) where it is nearly E-W to the area inboard of the Cocos ridge where it is NW-SE. This change suggests that background seismogenic deformation reflects the transition from the trailing edge of a fore-arc sliver to an area of the upper plate affected by ridge collision. This diffuse deformation may be localized, in part, on conjugate strike-slip faults of the CCRDB.

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“…Mientras que en AALJ el valor máximo fue de 415 cm/s 2 en PQSP fue de 231 cm/s 2 . Probablemente otros factores también influyan en estas diferencias como lo son posibles efectos de directividad de la fuente sísmica en el caso del sismo de Piedras Negras y falta de estos en el sismo de Damas (Pacheco et al, 2006), pero los efectos de sitio son claramente diferentes entre ambas estaciones, siendo mayor en AALJ.…”

Section: Discusión Y Resultadosunclassified

Inversión de efectos de sitio y factor Q utilizando cocientes espectrales

Fernández¹

2009

Estud. geol.

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Site effects and Q factor were inverted using the spectral ratio technique. The study area corresponds to central Costa Rica where the Earthquake Engineering Laboratory (INII-UCR) runs a strong motion network. The technique differs from the usual approach in that it makes use of a reference earthquake instead of a reference site. For that reason, the amplitude of the site effects that are obtained corresponds to the absolute amplification. The results indicate that stations located on soft sediment sites tend to have larger amplification values compared to other stations located on more compacted soils. The Q factor we obtained was frequency dependent with an approximate value of Q(f) = (131,6 ± 0,1)f (1,1 ± 0,2) .

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The Mw 6.4 Damas, Costa Rica, Earthquake of 20 November 2004: Aftershocks and Slip Distribution

Cited by 13 publications

References 29 publications

Three-dimensionalP-wave velocity structure on the shallow part of the Central Costa Rican Pacific margin from local earthquake tomography using off- and onshore networks

Three-dimensionalP-wave velocity structure on the shallow part of the Central Costa Rican Pacific margin from local earthquake tomography using off- and onshore networks

Collision versus sliver transport in the hanging wall at the Middle America subduction zone: Constraints from background seismicity in central Costa Rica

Inversión de efectos de sitio y factor Q utilizando cocientes espectrales

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