# Site-Specific Earthquake Ground Motions for Seismic Design of Port Facilities in Indonesia
## 1 Introduction
The amplification characteristics of EGMs strongly depend on ground profiles. Soft ground exhibits a nonlinear response during a massive earthquake. The degree of nonlinear response strongly depends on the ground profiles. Second, EGMs are governed by the source, path, and site amplification characteristics. Therefore, the ground motions observed in Indonesia must be analyzed to discuss the EGMs for seismic design in Indonesia. This study aimed to propose site-specific EGMs for the seismic design of port facilities in Indonesia. The ground is composed of both shallow and deep subsurfaces, and the \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**Site Class**} & \(V\)**s30 (m/s)** & \(\overline{N}\) & \(\overline{Su}\) **(kPa)** \\ \hline SA (hard rock) & \(>\)1500 & & Not applicable \\ \hline SB (rock) & 750–1500 & & Not applicable \\ \hline SC (very dense soil and soft rock) & 350–750 & \(>\)50 & \(\geq\)100 \\ \hline SD (stiff medium soil) & 175–350 & 15–50 & 50–100 \\ \hline \multirow{4}{*}{SE (soft clay soil)} & \(<\)175 & \(<\)15 & \(<\)50 \\  & Any site with more than 3 m of soil that has the following characteristics: & \\ \cline{1-1}  & - Plasticity index \(PI>20\); moisture content \(w\geq 40\%\) & \\ \cline{1-1}  & - Undrained shear strength \(\overline{Su}<25\) kPa & \\ \hline SF (special soil requiring site) & - For soils with a high risk of failure or collapse under seismic loadings & \\ \cline{1-1}  & (e.g., liquidable soils and quick and highly sensitive clays) & \\ \cline{1-1}  & - Peats and highly organic clays with soil thickness (\(H>3\) m) & \\ \cline{1-1}  & - Very-high-plasticity clays (\(H>7.5\) m) with \(PI>75\) & \\ \cline{1-1}   site investigation) & - Very thick, soft/medium-stiff clays (\(H>35\) m) with (\(\overline{Su}<50\) kPa) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Site class in the SNI. amplification factor of the EGM is much larger in the latter than in the former. Therefore, the effect of the deep subsurface should be appropriately considered for a site-specific EGM evaluation [13; 17; 18]. In addition, if there was information on the 3D ground structure down to the deep subsurface, EGMs were estimated using physics-based models [19; 20; 21; 22]. However, no data on the above were available; therefore, we focused only on the shallow subsurface amplification. If there was a number of EGM records available, the horizontal-to-vertical spectral ratio (HVSR) method [23; 24; 25] can be applied to evaluate the site class and site amplification factors. However, the number of EGM records is very small. Accordingly, we discussed site amplification factors based on borehole data. Port facilities are constructed on soft ground in coastal areas; thus, the SD and SE site classes were targeted. The EGM records obtained in Indonesia were collected, and the effects of the shallow subsurfaces at the observation sites were removed by a seismic response analysis to calculate the EGM incidents in the bedrock. The seismic waveforms in the bedrock were amplitude-adjusted so the PGA value agreed with that of the SNI bedrock. Next, the borehole data of the port areas in Indonesia were collected to construct ground models. The EGMs in the port areas were calculated by performing a seismic response analysis of 144 cases that considered the nonlinear characteristics of the shallow subsurfaces. Finally, we proposed EGMs for the seismic design of port facilities in Indonesia through a statistical processing of the obtained EGMs, and we compared these proposed EGMs with those in the current design code.