Inferring heterogeneity of fault properties and stress state of a megathrust fault from dynamic stress drop variations: A feasibility study in the northern Chilean subduction zone
Final Report Abstract
The principal objective of this research project was to contribute to a better understanding of earthquake rupture processes in subduction zones, and more specifically to resolve the role of stress and fault strength over different parts of the megathrust earthquake cycle. To achieve this, it was proposed to use stress drop as a primary marker. Therefore, the building of a comprehensive and robust stress drop map was the designated primary target of the project. This idea was realized for the northern Chilean subduction zone, where a recent large seismic catalog and excellent waveform data are available. Of the three initially planned stress drop estimation approaches, two approaches could be realized side by side, the spectral ratio method and the spectral decomposition method. First, a feasibility study using only the spectral ratios was implemented, followed by a large and robust stress drop catalog of over 51,000 estimates. This catalog, today, is amongst the largest compilations of stress drop, in general, and it resembles the only catalog covering an entire subduction zone from trench to a depth of about 200km. The great benefit of compiling a consistently processed catalog lies in the highly increased reliability of in-catalog variations of stress drop, which is usually difficult to compare between studies. The catalog revealed prior unknown features of stress drop variability: The stress drop segments the subduction tone into different regions, it is lowest all along the downgoing plate interface, highest in the upper plate crust and at great depth, where a depth dependency can be found. In combination with a b-value mapping, the comprehensive stress drop distribution was interpreted for assessing the nucleation conditions for earthquakes of different regions throughout the subduction zone. Analyzing spatio-temporal stress drop variability and the combination of such with remote sensing derived locking maps could not yet be realized and would be an important followup study worth pursuing. As an important byproduct of the search for suitable empirical Green’s functions for the spectral ratio derived stress drops large cross correlation matrices were computed. These have been searched extensively to identify repeating earthquakes in the target region. Improving methods and interpretation of the large number of repeaters and their variable characteristics have been started and will be continued in a subsequent project. The results will potentially be complementary to the stress drop catalog, which in itself bears a great potential fur further study.
Publications
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Dataset Publication for ’A Comprehensive Stress Drop Map from Trench to Depth in the Northern Chilean Subduction Zone.’ [data set]
Folesky, J., Pennington, C. N., Kummerow, J. & Hofman, L. J.
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Stress Drop Variations in the Region of the 2014 MW8.1 Iquique Earthquake, Northern Chile. Journal of Geophysical Research: Solid Earth, 126(4).
Folesky, Jonas; Kummerow, Jörn & Shapiro, Serge A.
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On Repeating Earthquakes in the Northern Chilean Subduction Zone.
Folesky, Jonas; Hofman, Rens & Kummerow, Jörn
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A Comprehensive Stress Drop Catalog for the Northern Chilean Subduction Zone, DGG Jahrestagung, Bremen, 2023
Folesky, J., Pennington, C. N., Kummerow, J. & Hofman, L. J.
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Benchmarking Study of EQTransformer Autopicker for Seismic Phase Identification in Northern Chile. EGU general assembly conference abstracts, 2022
Kasravi, J. & Folesky, J.
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Repeating Earthquakes in Northern Chile true Repeaters and Deep Repeaters. IUGG general assembly conference abstracts, 2023
Folesky, J., Hofman, L.J., Kummerow, J. & Schmidt, S.
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Stress Drop Segmentation in the Northern Chilean Subduction Zone: from Interface to Deep Seismicity. EGU general assembly conference abstracts, 2023
Folesky, J., Hofman, L.J. & Kummerow, J.
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A Comprehensive Stress Drop Map From Trench to Depth in the Northern Chilean Subduction Zone. Journal of Geophysical Research: Solid Earth, 129(1).
Folesky, J.; Pennington, C. N.; Kummerow, J. & Hofman, L. J.
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Different earthquake nucleation conditions revealed by stress drop and b-value mapping in the northern Chilean subduction zone. Scientific Reports, 14(1).
Folesky, Jonas
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Stress Drop Variation After Large Earthquakes, DGG Jahrestagung, Jena, 2024
Folesky, J.
