Seismological asperities from the point of view of dynamic rupture modeling: the 2007 Mw6.6 Chuetsu-Oki, Japan, earthquake

Abstract

We study the ground motion simulations based on three finite-source models for the 2007 Mw6.6 Niigata Chuetsu-oki, Japan, earthquake in order to discuss the performance of the input ground motion estimations for the near-field seismic hazard analysis. The three models include a kinematic source inverted from the regional accelerations, a dynamic source on a planar fault with three asperities inferred from the very-near-field ground motion particle motions, and another dynamic source model with conjugate fault segments. The ground motions are calculated for an available 3D geological model using a finite-difference method. For the comparison, we apply a goodness-of-fit score to the ground motion parameters at different stations, including the nearest one that is almost directly above the ruptured fault segments. The dynamic rupture models show good performance. We find that seismologically inferred earthquake asperities on a single fault plane can be expressed with two conjugate segments. The rupture transfer from one segment to another can generate a significant radiation; this could be interpreted as an asperity projected onto a single fault plane. This example illustrates the importance of the fault geometry that has to be taken into account when estimating the very-near-field ground motion.

Stress accumulation in the Marmara Sea estimated through ground‐motion simulations from dynamic rupture scenarios

“…This indicates that the model could be further improved locally to reflect the geological context. As well as considering a single ground‐motion parameter, such as PGV, we also calculate the goodness of fit (GoF) score between simulations and observations based on several metrics from each time series [ Olsen and Mayhew , ; Aochi and Yoshimi , ], averaged over long‐period spectral acceleration (SA) (10, 20, and 50 s), short‐period SA (1, 2, and 5 s), and duration defined as interval between 5 and 95% of Arias intensity. GoF for two positive values ( x , y ) to compare is calculated with where erfc is the complementary error function.…”

“…They also observed supersaturation (a large variation both in positive and negative senses) very close (less than 1 km) to the source. Although most of the studies are for planar faults, ground motion from dynamic rupture simulations based on nonplanar fault systems can also be coherent in terms of different metrics such as PGV, duration, and response spectral ordinates [ Aochi and Yoshimi , ].…”

Physics-Based Scenario of the 2007 Chuetsu-Oki Earthquake

“…In a second phase, they improved the coarse crustal model by refining it with a shallow structural model based on either 3D tomography, or on various 1D/2D profiles and geological interpretation. However, due to computational limits, their study is reliable within the frequency band 0.1-0.9 Hz (improved to 1.0 Hz in [20]), on a regional model 110 km ⇥ 120 km ⇥ 30 km. Tsuda et al [9] instead, tested the slip patch proposed by Shiba et al [16] focusing on the effect of the folding structure beneath the KKNPP and to its effects on the observed ground motion incoherence.…”