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TitleSource model and characteristics of the 27 July 2022 Mw 7.0 northwestern Luzon earthquake, Philippines
AuthorRimando, J M; Williamson, A L; Mendoza, R B C; Hobbs, T EORCID logo
SourceSeismica vol. 1, no. 1, 2022 p. 1-8, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20220267
Mediapaper; digital; on-line
File formatpdf
AreaLuzon; Philippines
Lat/Long WENS 120.0000 121.0000 18.0000 17.0000
SubjectsScience and Technology; tectonics; earthquakes; seismology; faults; satellites; remote sensing; radar methods; synthetic aperture radar surveys (SAR)
Illustrationslocation maps; satellite imagery; tables
ProgramPublic Safety Geoscience National Earthquake Risk Assessment Framework
Released2022 11 08
AbstractThe geometry and kinematics of the causative fault of the 27 July 2022 moment magnitude (MW) 7.0 earthquake, which is one of the strongest to hit northern and central Luzon in the past 30 years, were estimated through inverse modeling of line-of-site interferometric synthetic aperture radar deformation. We modeled rupture along multiple candidate faults based on fit with the pattern of line-of-site deformation, consistency with focal mechanisms, and compatibility with the known kinematics of the mapped active faults in the region. Our preferred fault model, located west of and parallel to the Abra River Fault, exhibits localized reverse-slip (average 67° rake) at 15-35 km down-dip. Peak slip occurs at a shallow depth (13-16 km), with 95 cm of pure reverse-slip. The existence of a reverse-slip dominated ARF-parallel fault rupture is consistent with a complex shear partitioning model, wherein the NW-SE oblique plate convergence is accommodated not only by the sinistral strike-slip Philippine Fault Zone and the major subduction zones, but also by minor faults in intervening crustal blocks.
Summary(Plain Language Summary, not published)
A magnitude 7.0 earthquake occurred in the Philippines on 27 July 2022, on the northern island of Luzon. The earthquake does not seem to have occurred on a known fault plane, given what is known about its surface displacement and the seismic energy it radiated. In this paper, we use satellite remote sensing data to try to determine the fault plane on which the earthquake ruptured. Although these data can be fit, to varying degrees, by different faults, our preferred model is a northerly aligned fault plane, dipping to the east. The slip on the fault is more vertical than horizontal, which is different from the other nearby mapped faults, which are primarily horizontal. This earthquake may be helping to accommodate NW-SE compressional stress in the Northern Philippines, caused by the motion of nearby tectonic plates.

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