Joint Regional Waveform, First Motion Polarity, and Surface Displacement Inversion Using a Layered Elastic Model With Topography for North Korean Nuclear Explosions
Description:
On September 7th 2017, The Democratic People’s Republic of North Korea carried out its latest and largest nuclear test (DPRK6) that registered Mw 5.2. Recent efforts have been made to increase understanding of this and previous nuclear tests using seismic waveform, and synthetic aperture radar (SAR) geodetic deformation data (e.g. Chiang et al. 2018, Myres et al. 2018, Wang et al. 2018). Additionally, in our previous work (Chi-Durán et al., 2021) we performed a joint regional waveform, first motion polarity, and surface displacement inversion demonstrating improved discrimination of the source-type of the event, obtained a revised moment tensor solution with reduced uncertainty in scalar moment, and constrained its location. In this work, we have applied the aforementioned joint inversion with a layered velocity model, informed on geologic structure interpretations of Pabian and Coblentz (2015) based on satellite imagery. We propose a 4-layered model, composed of a 50-m basalt layer (Vp =1.9 km/s, Vs=1.1 km/s), 100-m stratified volcanic deposit layer (Vp=2.08 km/s, Vs=1.2 km/s), 150-m granodiorite layer (Vp= 2.6 km/s , Vs= 1.5 km/s) over a half-space (Vp=5.35 km/s, Vs=3.09 km/s) which shares the velocity of the regional MDJ2 velocity model (Ford et al. 2009) which has proven effective in waveform inversion for the region. This model considers the range of reported values for the different lithologies and also weathering effects over the top layers. We find that the consideration of the layered velocity model improves the recovery of source depth. Furthermore, we tested this layered model with an earlier, smaller explosion (DPRK4) that occurred on January 6, 2016, inverting regional waveforms, first-motion polarity and line-of-sight (LOS) deformation from ALOS-2 InSAR data. In this case, the joint inversion is found to provide better discrimination of the source-type and better constrain the scalar seismic moment needed for downstream yield estimation.
Session: Exploiting Explosion Sources: Advancements in Seismic Source Physics
Type: Oral
Date: 4/19/2023
Presentation Time: 02:00 PM (local time)
Presenting Author: Rodrigo Chi-Duran
Student Presenter: Yes
Invited Presentation:
Authors
Rodrigo Chi-Duran Presenting Author Corresponding Author rodrigo.chi@berkeley.edu University of California, Berkeley |
Douglas Dreger ddreger@berkeley.edu University of California, Berkeley |
Arthur Rodgers rodgers7@llnl.gov Lawrence Livermore National Laboratory |
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Joint Regional Waveform, First Motion Polarity, and Surface Displacement Inversion Using a Layered Elastic Model With Topography for North Korean Nuclear Explosions
Category
Exploiting Explosion Sources: Advancements in Seismic Source Physics