Yoshito Yokoe

Evaluation of seismic risk in Yangon City using empirical seismic motion evaluation method

Takaaki Ikeda

The distance decay equation is a simple method for evaluating earthquake risk. However, although the distance attenuation method has the advantage of easy risk assessment, it does not take into account detailed fault parameters such as directional effects of fault rupture and fault heterogeneity. However, it cannot take into account detailed fault parameters such as fault rupture directional effects and fault heterogeneity. Therefore, this study aims to conduct risk assessment using the waveform synthesis method in Myanmar.
As a background to the study of Myanmar, a project called "Strengthening the Disaster Response System in Myanmar and Building a Platform for Industry-Academia-Government Collaboration" is underway as part of SATREPS, a joint research program between researchers in developing countries and JICA. In this program, research is being conducted to determine the ground amplification factor in Yangon and to calculate the damage to buildings. However, the earthquake ground motions used in these studies are considered to be 30kine unified. Therefore, in this study, we use waveform synthesis in Yangon to obtain detailed engineering basis.
In this study, the earthquake ground motions from six faults are assumed based on the past earthquake history and literature. For reference, we also considered an inland earthquake of M7 class directly under Yangon City. We used EMPR, an empirical seismic prediction method that can take into account detailed fault parameters such as fault heterogeneity and directional effects of fault rupture. The fault parameters required for EMPR are the fault length, width, seismic moment, fault strike, fault dip, moment ratio of each sub-fault, and the relative position of the fault to the site (Xs, Ys). The fault parameters were basically set according to the strong-motion prediction recipe.
The strong motion prediction recipe is a standard methodology to predict the strong motion of an earthquake with high accuracy by specifying the source fault. The evaluation points are divided into a mesh of Yangon city at intervals of 1 km, 30 km long by 25 km wide. The ground amplification factor obtained from the study of Matsumoto (2020) was used as the ground amplification factor and interpolated into the mesh. The results showed that the seismic waves amplified in the direction of rupture from the north to the south, and there were no cases where the amplification exceeded 30 kine. The reason for the amplification of seismic waves is the fault directionality effect. In addition, we found that the seismic motions on the engineering basis, assuming past faults, did not produce results exceeding 30 kine.
In Yangon, the seismic resistance of buildings tends to be weaker than in Japan, so I believe that the earthquake ground motions obtained in this study can be effectively used to calculate the damage.