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  • 1
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    Integration of Arrival-Time Datasets for Consistent Quality Control: A Case Study of Amphibious Experiments along the Middle America Trench (2013)
    Seismological Society of America
    In:  Bulletin of the Seismological Society of America, 103 (5). pp. 2752-2766.
    Details
    Publication Date: 2019-09-23
    Description: We have integrated waveform and arrival-onset data collected in Costa Rica as part of the National Science Foundation (NSF)-sponsored Costa Rica Seismogenic Zone Experiment (CRSEIZE) and along central Costa Rica and Nicaragua as part of the German SFB 574 program. The five arrays, composed of different sensor types (one-and three-component land and ocean bottom seismometers and hydrophones), were archived using different software packages (Antelope and SEISAN) and were automatically and manually picked using various quality criteria resulting in a disparate set of pick weights. We evaluate pick quality using automated arrival detection and picking algorithm based on the wavelet transform and Akaike information criterion picker. The consistency of the arrival information over various scales provides a basis for assigning a quality to the analyst pick. Approximately 31% of P arrival times and 26% of S times have been classified as high-quality picks (quality 0-1). An additional 21% of P times and 27% of S arrivals are good quality (quality 2-3). The revised quality picks are mapped directly into new pick weights for inversion studies. We explore the effect of new weighting and removal of poor data by relocating hypocenters through a minimum 1D velocity model and conducting double-difference local earthquake tomography (LET). Analysis of the hypocenter relocation and seismic velocity tomography results suggest that using the improved quality determinations have a greater effect on improving sharpness in the velocity images than on the magnitude of hypocentral movement.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1785/0120120274
    Location Call Number Limitation Availability
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Mantle subducting slab structure in the region of the 2010 M8.8 Maule earthquake (30-40°S), Chile (2012)
    Wiley
    In:  Geophysical Journal International, 191 (1). pp. 317-324.
    Details
    Publication Date: 2016-06-22
    Description: We present a new tomographic model of the mantle in the area of the 2010 M8.8 Maule earthquake and surrounding regions. Increased ray coverage provided by the aftershock data allows us to image the detailed subducting slab structure in the mantle, from the region of flat slab subduction north of the Maule rupture to the area of overlapping rupture between the 1960 M9.5 and the 2010 M8.8 events to the south. We have combined teleseismic primary and depth phase arrivals with available local arrivals to better constrain the teleseismic earthquake locations in the region, which we use to conduct nested regional–global tomography. The new model reveals the detailed structure of the flat slab and its transition to a more moderately dipping slab in the Maule region. South of the Maule region, a steeply dipping relic slab is imaged from ∼200 to 1000 km depth that is distinct from the moderately dipping slab above it and from the more northerly slab at similar depths. We interpret the images as revealing both horizontal and vertical tearing of the slab at ∼38°S to explain the imaged pattern of slab anomalies in the southern portion of the model. In contrast, the transition from a horizontal to moderately subducting slab in the northern portion of the model is imaged as a continuous slab bend. We speculate that the tearing was most likely facilitated by a fracture zone in the downgoing plate or alternatively by a continental scale terrane boundary in the overriding plate.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-246X.2012.05624.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    P-wave Velocity Modeling Using Onshore/Offshore Passive Seismic Networks Along the Middle America Subduction Zone, Costa Rica and Nicaragua (2008)
    In:  [Talk] In: AGU Fall Meeting, 15-19 December, San Francisco, USA .
    Details
    Publication Date: 2012-01-27
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Talk
  • 4
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    Seismogenic zone structure beneath the Nicoya Peninsula, Costa Rica, from three-dimensional local earthquake P- and S-wave tomography (2006)
    Wiley
    In:  Geophysical Journal International, 164 (1). pp. 109-124.
    Details
    Publication Date: 2018-07-16
    Description: The subduction plate interface along the Nicoya Peninsula, Costa Rica, generates damaging large (Mw 〉 7.5) earthquakes. We present hypocenters and 3-D seismic velocity models (VP and VP/VS) calculated using simultaneous inversion of P- and S-wave arrival time data recorded from small magnitude, local earthquakes to elucidate seismogenic zone structure. In this region, interseismic cycle microseismicity does not uniquely define the potential rupture extent of large earthquakes. Plate interface microseismicity extends from 12 to 26 and from 17 to 28 km below sea level beneath the southern and northern Nicoya Peninsula, respectively. Microseismicity offset across the plate suture of East Pacific Rise-derived and Cocos-Nazca Spreading Center-derived oceanic lithosphere is ∼5 km, revising earlier estimates suggesting ∼10 km of offset. Interplate seismicity begins downdip of increased locking along the plate interface imaged using GPS and a region of low VP along the plate interface. The downdip edge of plate interface microseismicity occurs updip of the oceanic slab and continental Moho intersection, possibly due to the onset of ductile behaviour. Slow forearc mantle wedge P-wave velocities suggest 20–30 per cent serpentinization across the Nicoya Peninsula region while calculated VP/VS values suggest 0–10 per cent serpentinization. Interpretation of VP/VS resolution at depth is complicated however due to ray path distribution. We posit that the forearc mantle wedge is regionally serpentinized but may still be able to sustain rupture during the largest seismogenic zone earthquakes.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1111/j.1365-246X.2005.02809.x
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Seismogenic zone structure of the southern Middle America Trench, Costa Rica (2003)
    AGU (American Geophysical Union)
    In:  Journal of Geophysical Research: Solid Earth, 108 (B10). p. 2491.
    Details
    Publication Date: 2018-05-30
    Description: The shallow seismogenic portion of subduction zones generates damaging large and great earthquakes. This study provides structural constraints on the seismogenic zone of the Middle America Trench offshore central Costa Rica and insights into the physical and mechanical characteristics controlling seismogenesis. We have located ~300 events that occurred following the MW 6.9, 20 August 1999, Quepos, Costa Rica, underthrusting earthquake using a three-dimensional velocity model and arrival time data recorded by a temporary local network of land and ocean bottom seismometers. We use aftershock locations to define the geometry and characteristics of the seismogenic zone in this region. These events define a plane dipping at 19° that marks the interface between the Cocos Plate and the Panama Block. The majority of aftershocks occur below 10 km and above 30 km depth below sea level, corresponding to 30–35 km and 95 km from the trench axis, respectively. Relative event relocation produces a seismicity pattern similar to that obtained using absolute locations, increasing confidence in the geometry of the seismogenic zone. The aftershock locations spatially correlate with the downdip extension of the oceanic Quepos Plateau and reflect the structure of the main shock rupture asperity. This strengthens an earlier argument that the 1999 Quepos earthquake ruptured specific bathymetric highs on the downgoing plate. We believe that subduction of this highly disrupted seafloor has established a set of conditions which presently limit the seismogenic zone to be between 10 and 35 km below sea level.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2002JB002294
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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