Logarithmic Model Joint Inversion Method for Coseismic and Postseismic Slip: Application to the 2017 Mw 7.3 Sarpol Zahāb Earthquake, Iran

Abstract

Interferometric synthetic aperture radar (InSAR) has become an important technique for studying earthquake cycle deformation. However, due to the limited satellite revisit time, it is often difficult to fully separate coseismic and postseismic slip from InSAR data. Nevertheless, accurately estimating spatiotemporal coseismic and postseismic fault slip distribution models is important for quantifying earthquake slip, understanding the kinematics of seismogenic faulting, and evaluating seismic hazards. Here, we develop a logarithmic model-based method (LogSIM) for the joint inversion of coseismic and postseismic fault slip using InSAR data from multiple platforms in different orbits. This method considers the nature of early postseismic slip following logarithmic decay. The coseismic slip, the decay time constant, and the decay amplitude of the logarithmic model can be jointly estimated from unwrapped interferograms without the need for InSAR time series calculations, thereby reducing the number of unknown parameters and stabilizing the inversion. The robustness of LogSIM is first validated with synthetic experiments. We then apply LogSIM to invert for the coseismic and postseismic slip models of the 2017 Mw 7.3 Sarpol Zahāb earthquake. We find that the maximum afterslip value and postseismic moment release during the first four months reported in previous studies are underestimated by~26% and~31%, respectively, due to the unavailability of the first five days of postseismic deformation. The estimated afterslip distribution spatially overlaps with the aftershocks in the updip region of the fault plane. LogSIM could potentially be extended to integrate different space geodetic data in earthquake cycle deformation modeling.

The 2018 Mw 7.5 Papua New Guinea Earthquake: A Possible Complex Multiple Faults Failure Event With Deep‐Seated Reverse Faulting

“…Such properties can hinder the brittle failure when the dynamic ruptures propagate into the area. Given that reverse fault systems usually have imbricate or duplex structures (Boyer & Elliott, 1982), the limited shallow slip is not uncommon and has also been observed in other fold‐and‐thrust belts, for example, the northwest Zagros belt where ramp‐décollement structures were inferred in the 2017 M w 7.3 Iran earthquake (Feng et al, ; Liu & Xu, ). In our study, seismic evidences show that fault networks across the PFTB tend to form imbricate structures within the upper 10 km of the crust (Callot et al, ; Hanani et al, ; Hill et al, ).…”

Resolving the Kinematics and Moment Release of Early Afterslip within the First Hours following the 2016 Mw 7.1 Kumamoto Earthquake: Implications for the Shallow Slip Deficit and Frictional Behavior of Aseismic Creep

“…Most geodetic imaging data (e.g., Interferometric Synthetic Aperture Radar, InSAR) are acquired within the first days to weeks following rupture, which makes it challenging to constrain how contaminated current fault slip models are and how biased estimates of the SSD could be from early and possibly rapid afterslip. Recently proposed dual-inversion approaches that jointly solve for both coseismic and postseismic slips with data sets spanning mixed time periods show promise in addressing this issue in the future but require the availability of continuous and high spatialdensity that are limited by possible trade-offs (Liu & Xu, 2019;Ragon et al, 2019). Instances where rapid shallow afterslip could be observed include the 2014 M w 6.0 Napa earthquake (Lienkaemper et al, 2016) and the 2004 M w 6.0 Parkfield earthquake (Freed, 2007), where measurements were acquired early enough to separate early afterslip from coseismic slip in the shallow crust.…”

Improving the Resolving Power of InSAR for Earthquakes Using Time Series: A Case Study in Iran

“…where ( * ) is a Heaviside step function, represents the coseismic displacement, and are the parameters for a logarithmic function representing the postseismic deformation (Ingleby & Wright, 2017;Liu & Xu, 2019), is the long-term linear deformation rate which contains in part the interseismic displacement, and b is a constant reference offset in observations.…”