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Abstract The role of upper‐plate faulting in the seismic cycle of large megathrust earthquakes remains poorly understood. We use quasi‐dynamic numerical simulations of seismic cycles to analyze the interaction between crustal faulting and the foreshock sequence of the 2014 Iquique (Mw 8.2) earthquake in Northern Chile. Multi‐cycle models incorporating upper‐plate faulting align better with coseismic displacements, replicating events akin to the Iquique earthquake. Upper‐plate faulting significantly influences foreshock seismicity and deformation patterns. By calibrating the average hydraulic state—varying the effective normal stress—along the megathrust with pre‐earthquake seismicity, we find that lower pore pressure ratios result in more seismicity before the mainshock. This implies that the hydraulic state of the megathrust is critical for foreshock activity. This comprehensive modeling approach underscores the importance of the mechanical interplay between the megathrust and upper‐plate faults in precursory sequences of large subduction zone earthquakes.
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Tracking the Spatio‐Temporal Evolution of Foreshocks Preceding the Mw 6.1 2009 L’Aquila Earthquake
Abstract How faulting processes lead to a large earthquake is a fundamental question in seismology. To better constrain this pre‐seismic stage, we create a dense seismic catalog via template matching to analyze the precursory phase of the Mw 6.1 L’Aquila earthquake that occurred in central Italy in 2009. We estimate several physical parameters in time, such as the coefficient of variation, the seismic moment release, the effective stress drop, and analyze spatio‐temporal patterns to study the evolution of the sequence and the earthquake interactions. We observe that the precursory phase experiences multiple accelerations of the seismicity rate that we divide into two main sequences with different signatures and features: the first part exhibits weak earthquake interactions, quasi‐continuous moment release, slow spatial migration patterns, and a lower effective stress drop, pointing to aseismic processes. The second sequence exhibits strong temporal clustering, fast seismicity expansion, and a larger effective stress drop typical of a stress transfer process. We interpret the differences in seismicity behaviors between the two sequences as distinct physical mechanisms that are controlled by different physical properties of the fault system. We conclude that the L’Aquila earthquake is preceded by a complex preparation, made up of different physical processes over different time scales on faults with different physical properties.
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- PAR ID:
- 10368220
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Solid Earth
- Volume:
- 127
- Issue:
- 3
- ISSN:
- 2169-9313
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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