Stress Drop Variations in the Region of the 2014 MW8.1 Iquique Earthquake, Northern Chile
Folesky, Jonas; Kummerow, Jörn; Shapiro, Serge A., 2021: Stress Drop Variations in the Region of the 2014 MW8.1 Iquique Earthquake, Northern Chile. In: Journal of Geophysical Research: Solid Earth, Band 126, 4, DOI: 10.23689/fidgeo-4272.
|
View/
|
We compute stress drops from P and S phase spectra for 534 earthquakes in the source region of the 2014 MW8.1 Iquique megathrust earthquake in the northern Chilean subduction zone. An empirical Green's function based method is applied to suitable event pairs selected by template matching of eight years of continuous waveform data. We evaluate the parameters involved in the stress drop estimation, consider the effect of the local velocity structure and apply an empirical linear relation between P and S phase related geometry factors (k values). Data redundancy produced by multiple empirical Green's function and the combination of P and S phase spectra leads to a substantial reduction of uncertainty and robust stress drop estimates. The resulting stress drop values show a well‐defined log‐normal distribution with a median value of 4.36 MPa; most values range between 0.1 and 100 MPa. There is no evidence for systematic large scale lateral variations of stress drop. A detailed analysis reveals several regions of increased median stress drop, an increase with distance to the interface, but no consistent increase with depth. This suggests that fault regime and fault strength have a stronger impact on the stress drop behavior than absolute stresses. Interestingly, we find a weak time‐dependence of the median stress drop, with an increase immediately before the April 1, 2014 MW8.1 Iquique mainshock, a continuous reduction thereafter and a subsequent recovery to average values. Additionally, the data set indicates a relatively strong dependence of stress drop on magnitude which extends over the entire analyzed magnitude range. Key Points:
A comprehensive stress drop distribution for the Iquique Earthquake rupture region is computed using a spectral ratio approach.
The stress drops estimates reveal no large scale pattern or major trend such as a depth dependency.
We describe minor stress drop variations in greater detail and find a relatively strong scaling with moment for the entire data set.
Statistik:
View StatisticsCollection
Subjects:
brune type stress dropnorthern Chile
spatio‐temporal variability
spectral ratio
subduction interface seismicity
template matching
This is an open access article under the terms of the Creative Commons Attribution‐NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.