Publication Date:
2021-02-02
Description:
Finite-fault models for the 2010 Mw 8.8 Maule, Chile earthquake indicate bilateral rupture
with large-slip patches located north and south of the epicenter. Previous studies also
show that this event features significant slip in the shallow part of the megathrust, which is
revealed through correction of the forward tsunami modeling scheme used in tsunami
inversions. The presence of shallow slip is consistent with the coseismic seafloor
deformation measured off the Maule region adjacent to the trench and confirms that
tsunami observations are particularly important for constraining far-offshore slip. Here, we
benchmark the method of Optimal Time Alignment (OTA) of the tsunami waveforms in the
joint inversion of tsunami (DART and tide-gauges) and geodetic (GPS, InSAR, landleveling)
observations for this event. We test the application of OTA to the tsunami
Green’s functions used in a previous inversion. Through a suite of synthetic tests we
show that if the bias in the forward model is comprised only of delays in the tsunami signals,
the OTA can correct them precisely, independently of the sensors (DART or coastal tidegauges)
and, to the first-order, of the bathymetric model used. The same suite of
experiments is repeated for the real case of the 2010 Maule earthquake where,
despite the results of the synthetic tests, DARTs are shown to outperform tidegauges.
This gives an indication of the relative weights to be assigned when jointly
inverting the two types of data. Moreover, we show that using OTA is preferable to
subjectively correcting possible time mismatch of the tsunami waveforms. The results for
the source model of the Maule earthquake show that using just the first-order modeling
correction introduced by OTA confirms the bilateral rupture pattern around the epicenter,
and, most importantly, shifts the inferred northern patch of slip to a shallower position
consistent with the slip models obtained by applying more complex physics-based
corrections to the tsunami waveforms. This is confirmed by a slip model refined by
inverting geodetic and tsunami data complemented with a denser distribution of GPS data
nearby the source area. The models obtained with the OTA method are finally
benchmarked against the observed seafloor deformation off the Maule region. We find
that all of the models using the OTA well predict this offshore coseismic deformation, thus
overall, this benchmarking of the OTA method can be considered successful.
Description:
Published
Description:
585429
Description:
3T. Sorgente sismica
Description:
6T. Studi di pericolosità sismica e da maremoto
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Permalink
