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Detection and Location of the Oceanic Intraplate Earthquakes at the Oldest Pacific Plate Using Pacific Array (Oldest-1) Data
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DOI：10.1785/0220240336.png)
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Abstract
En 中文
Oceanic intraplate earthquakes are closely associated with seafloor geologic features, such as knolls, fracture zones, and seamounts. However, this inference is often challenged by significant earthquake location uncertainties and difficulties in detecting small earthquakes, largely owing to limited station coverage. In this study, we used ocean-bottom seismometer data from the Oldest-1 array consisting of 12 sites, which is part of the Pacific array, to construct a one-year earthquake catalog for intraplate events on the oldest Pacific plate (similar to 170-180 Ma), similar to 900 km east of the Mariana trench. This catalog includes 17 small intraplate earthquakes of magnitude m(b)(Sn) 0.9-3.7 that occur within the array (<700 km from the array center). Although their small magnitudes and sparse station coverage, with an average interstation distance of similar to 393 km did not permit the estimation of focal depths and mechanisms, (re)located events with horizontal location errors of 2-8 km highlight a clear zone of deformation within the plate. Of the 17 earthquakes, 13 occurred in close proximity to seafloor geologic features. We found that five events with m(b)(Sn) 0.9-1.6, located near knolls, exhibited high waveform similarity (correlation coefficient exceeding 0.92) and colocation within an 80x80 m(2) area, suggesting that they could be repeating earthquakes. The occurrence of five other events with m(b)(Sn) 1.3-2.2 at/near an old fracture zone (similar to 160 Ma) may indicate that the fracture zone may be seismically active regardless of its age. Conversely, three events with m(b)(Sn) 2.9-3.7, which show clear T-phase signals are located near seamounts, suggesting the reactivation of pre-existing faults. Our results provide a tighter spatial correlation between epicenters and zones of existing weakness on the seafloor as well as an avenue for detailing waveform characteristics in future experiments.
Keywords:
FRACTURE-ZONES
CONTINENTAL-MARGIN
SEISMIC PHASE
T-PHASES
STRESSES
SEISMOMETER
REGIONS
FLEXURE
NOISE
BASIN
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