Range of distributed fault rupture - strike-slip and reverse-slip faulting -

Abstract:

When an earthquake occurs, surface ruptures are distributed not only on main faults but also around them. Therefore, an evaluation of fault rupture zones is important for a fault displacement hazard. Boncio et al. (2018) summarized the width of distributed fault rupture zones of reverse fault based on compiled fault displacement data. They classified distributed faults into several categories according to the fault scarp shapes. On the other hand, Petersen et al. (2011) compiled strike-slip fault data to construct the Probabilistic Fault Displacement Hazard Analysis (PFDHA) model, and they provide the functions of the occurrence probability and fault displacement attenuation curve of distributed fault. Their distributed fault data are not classified unlike Boncio et al. (2018). Histograms of the distance of distributed faults from principal faults compiled by Boncio et al. (2018) and Petersen et al. (2011) were used to compare distributed fault rupture zones of the reverse fault and strike-slip fault under the same condition.

In the hanging wall data of the reverse fault, the frequency distribution decreases to 1500 m from the principal fault, whereas in the strike-slip fault, the frequency distribution gradually decreases toward further distance, and the range of the distribution extends up to about 12 km. On the foot wall side data of the reverse fault, the frequency distribution sharply decreases to 1000 m from the principal fault. Ranges of the sympathetic distributed faults of Boncio et al. (2018) compiled data, which are ruptures that have occurred on an existing structure, exceeds over 2000m from the principal faults, and indicate wider range than that of other distributed fault rupture type. Petersen et al. (2011) indicated many of distant distributed faults of their data were triggered ruptures. Many distributed faults over 5000m from the principal faults of Petersen et al. (2011) data occurred on the existing faults and geological structures.

The distributed fault of strike-slip fault tended to be distributed over a wider range than that of reverse faults. This trend is similar to the fault displacement attenuation functions of distributed faults. Furthermore, existing active faults and geological structures are one of the important factor to cause distant distributed faults.