Physics-based dynamic rupture models, fault interaction and ground motion simulations for the segmented Húsavík-Flatey Fault Zone, Northern Iceland

Abstract

We present 3-D spontaneous dynamic rupture earthquake scenarios for the Húsavík-Flatey Fault Zone (HFFZ) in Northern Iceland. We construct three fault system models consisting of up to 55 segments of varying geometric complexity. By varying hypocenter locations, we analyze rupture dynamics, fault interactions and their associated ground motions and observational uncertainties in 79 scenarios. We use regional observations to constrain 3-D subsurface velocities and viscoelastic attenuation as well as fault stress and strength. Our models account for topo-bathymetry, off-fault plasticity and we explore the effect of fault roughness. Our spontaneous dynamic rupture scenarios can match historic magnitudes. We show that the fault system segmentation and geometry, hypocenter locations, initial stress conditions and fault roughness have strong effects on multi-fault rupture dynamics across the HFFZ. Breaking of different portions of the same fault system leads to varying rupture dynamics, slip distributions and magnitudes. All dynamic rupture scenarios yield highly heterogeneous near-field ground motions. We observe amplification from rupture directivity, geometric complexities, and amplification and shielding due to topography. We recover a magnitude-consistent attenuation relationship in good agreement with new regional empirical ground motion models. Physics-based ground motion variability changes with distance and increases for unilateral vs. bilateral rupture. Our study illustrates important ingredients for fully physics-based, regional earthquake scenarios, their respective importance for rupture dynamics and ground motion modeling and how they can be observationally constrained and verified. We entail that dynamic rupture scenarios can be useful for non-ergodic probabilistic seismic hazard assessment, specifically in data-limited regions.

Towards physics-based PSHA using CyberShake in the South Iceland Seismic Zone

“…The estimated fault extents of historical earthquakes, and in particular those of the recent 𝑀 w 6.3-6.5 earthquakes in 2000 and 2008, show a much smaller relative fault area and relatively large slip than expected by most scaling laws (see e.g., Pedersen et al 2003;Dubois et al 2008;Hreinsdóttir et al 2009;Decriem et al 2010). However, the "effective source area" scaling law of shallow crustal interplate strike-slip earthquakes of Mai and Beroza (2000) has been found to describe well the total area of earthquakes in the SISZ-RPOR and has been applied here in accordance with the original study (Bayat et al 2022) and subsequent applications (Kowsari et al 2022a;Li et al 2023). We show in Figure 4 examples of two rupture variations for hypothetical 𝑀 w 6 and Mw 7 events.…”

“…In the last 1-2 decades, however, computational seismology using high-performance computing (HPC) has explored physical models to explain the mechanisms that govern earthquake rupture and seismic wave propagation. When modeling earthquake ruptures, kinematic models prescribe finite slip evolution in space and time and allow to explore variability in seismic moment, fault orientation, hypocenter location, source time function, and rupture path, while dynamic rupture models (e.g., Li et al 2023) use the physics of frictional rock failure to model how earthquakes start, dynamically propagate and arrest and may probe in addition to the variability in kinematic models also differences in fault frictional parameters, coseismic multi-fault interaction and local stress distributions. The sampling of source parameters and their variability combined with the simulation of wave propagation accounting for wave-physics effects has allowed a physics-based approach to PSHA (Graves et al 2011;Bradley et al 2018;Callaghan et al 2021;Milner et al 2021).…”

Research on Multibeam Bathymetric System Based on Geometrical Relation Mo Model

“…The system transmits and receives acoustic waves in a wide range of angles through an array of acoustic transmitter and receiver transducers, forming a strip-type high-density bathymetric data, capable of mapping the three-dimensional topography and geomorphology of the seafloor within a certain width of the strip along the route, taking into account the changes in the seafloor topography around the underwater structure [2]. The existence of beam overlapping areas in multibeam surveys is unavoidable, and it is also necessary to pay attention to the situation of missed measurements.…”