11:30 AM - 11:45 AM
[SSS11-15] Improvement of Ground Motion Prediction Equation for Very Close to Long Active Fault
Keywords:Strong-motion prediction, Ground motion prediction equation , Long active fault, Site very close to the fault
We have constructed a seismic motion prediction equation using a dataset that includes strong-motion records of the 2011 great Tohoku earthquake (Mj9.0; Morikawa and Fujiwara, 2013; hereafter MF13). The MF13 prediction is based on the data set from Kanno et al. (2003), which includes records of major earthquakes that occurred before the start of K-NET observations, such as the 1968 Tokachi-oki (Mj7.9) earthquake and the 1995 Hyogo-ken Nanbu (Kobe) earthquake (Mj7.3). The MF13 predictions are generally consistent with the 2016 Kumamoto earthquake (Mj7.3) and the 2024 Noto Peninsula earthquake (Mj7.6) in the 0.1- to 10-second period range, although there is a slight underestimation tendency on the short-period range for the 2018 East Iburi, Hokkaido earthquake.
On the other hand, for the Kahramanmaras earthquake (Mw 7.7) that occurred on February 6, 2023 at 4:17 UTC, many strong-motion records were obtained very close to the source fault (within a few kilometers). The MF13 data set includes records of earthquakes of Mw7 or less within 10 km of the shortest fault distance, but no records of larger earthquakes within 30 km of the shortest fault distance, and the near-source predictions are extrapolated for earthquakes of Mw7 and above. MF13 is a model that can explain large-amplitude ground motions with a period of about 1 second observed in the very close to the source fault with a Mw of 6 or greater earthquakes, such as the 1995 Hyogo-ken Nanbu earthquake and the 2004 Niigata-ken Chuetsu earthquake, because the coefficient value of the term related to the amplitude saturation at short distances with a period of 0.5 to 3 seconds is small. However, this may lead to an overestimation because the effect of the amplitude saturation at short distances is small even for magnitudes above the latter half of Mw7
Based on the above, we will improve the MF13 for very close a long active fault with a period of 1 second. Specifically, using the observation records of the Kahramanmaras earthquake, we will examine the coefficient values of the terms related to the amplitude saturation at short distances.
On the other hand, for the Kahramanmaras earthquake (Mw 7.7) that occurred on February 6, 2023 at 4:17 UTC, many strong-motion records were obtained very close to the source fault (within a few kilometers). The MF13 data set includes records of earthquakes of Mw7 or less within 10 km of the shortest fault distance, but no records of larger earthquakes within 30 km of the shortest fault distance, and the near-source predictions are extrapolated for earthquakes of Mw7 and above. MF13 is a model that can explain large-amplitude ground motions with a period of about 1 second observed in the very close to the source fault with a Mw of 6 or greater earthquakes, such as the 1995 Hyogo-ken Nanbu earthquake and the 2004 Niigata-ken Chuetsu earthquake, because the coefficient value of the term related to the amplitude saturation at short distances with a period of 0.5 to 3 seconds is small. However, this may lead to an overestimation because the effect of the amplitude saturation at short distances is small even for magnitudes above the latter half of Mw7
Based on the above, we will improve the MF13 for very close a long active fault with a period of 1 second. Specifically, using the observation records of the Kahramanmaras earthquake, we will examine the coefficient values of the terms related to the amplitude saturation at short distances.