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Seismic Performance Assessment of Sustainable Shelter Building Using Microtremor Method Putra, Rusnardi Rahmat; Kiyono, Junji; Ono, Yusuke; Saputra, Dezy
Civil Engineering Journal Vol 10, No 11 (2024): November
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2024-010-11-06

Abstract

The increasing intensity of earthquakes in West Sumatra could trigger megathrust earthquakes and tsunamis at the inter-plate in the Mentawai Islands. Building assessments are necessary to determine their vulnerability to predicted earthquakes. The target is a four-story building that serves as an education building and vertical evacuation. This research proposes a complete vulnerability assessment method using single microtremor observations, and the results are used to determine seismic building performance. The natural frequency is derived from the spectral analysis of the horizontal components (NS and EW) for each level, and we considered the largest earthquake peak ground motion (PGA) in this region to be the September 30, 2009, Padang earthquake (PGA 380 gals as ground motion input). We calculated the resonance index, seismic vulnerability index, and damping ratio. The results show that the resonance index of the structure is less than 1, the vulnerability index of the UNP Faculty of Economics building ɤ > (1/100-1/200) and is 1/234 to 1/699 for the x direction and 1/207 to 1/709 for the y direction; the average damping ratio is <5% for both directions (x, y) and RDM and FSR relationship is 0.78 and 0.69 for x and y respectively. The overall findings indicate that the structural response of the evaluated buildings falls within the 'slight' damage category during seismic events. Doi: 10.28991/CEJ-2024-010-11-06 Full Text: PDF
Natural Frequency of Liquefaction Potential Based on Soil Investigation and Microtremor Observation Results Putra, Rusnardi Rahmat; Kiyono, Junji; Zhang, Zhenghu; Vanapalli, Sai; Agung, M. Darma
Civil Engineering Journal Vol. 11 No. 8 (2025): August
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.28991/CEJ-2025-011-08-02

Abstract

This study aims to identify the natural frequency threshold for liquefaction potential by comparing four assessment methods at 54 identical sites in Padang, Indonesia. Methods include: (1) safety factor calculations from soil investigation results (CPT and SPT) applying the 2009 Padang earthquake's peak ground acceleration as input for cycling stress ratio; (2) natural frequency measurements at the surface using microtremor single observations; (3) liquefaction potential assessment through vulnerability index; and (4) analysis of historical liquefaction events from the September 30, 2009 Padang earthquake documented in two previous research papers. The analysis focused on soil depths ranging from 1-4 m. Findings reveal that sites with natural frequencies exceeding 0.40 Hertz remain safe from liquefaction, while sites with frequencies between 0.20-0.39 Hertz demonstrate significant liquefaction potential. This research contributes to the field by establishing a clear correlation between measurable natural frequency thresholds and liquefaction risk, providing engineers and urban planners with a more accessible parameter for preliminary risk assessment. Integrating multiple assessment methods at identical sites enhances the reliability of the identified frequency thresholds, offering a more comprehensive approach to liquefaction hazard mitigation in earthquake-prone regions.
Estimation of Strong Ground Motion at Mandalay Region, Myanmar thein, pyi soe; Khaing, Khaing; Lin, Kyi Kyi; Pramumijoyo, Subagyo; Kiyono, Junji
Journal of Applied Geology Vol 10, No 1 (2025)
Publisher : Geological Engineering Department Universitas Gadjah Mada

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.22146/jag.105847

Abstract

Mandalay region lies very closed to the dextral Sagaing fault. In the historical record, several earthquakes happened in and around Mandalay region from the beginning of the year of 1400. Among them the most distinct event is the Sagaing earthquake struck on July 16, 1956. This research mainly focuses on results of microtremor survey at 143 sites and 25 data from the boreholes for determination of sediment thickness characteristics and strong ground motion analysis in Mandalay region. For the accurate prediction of earthquake ground motions, the investigation of three elements in its process, namely the source, path, and site effects, is crucial, and their accuracy and reliability should be evaluated. The subsurface profiles, predominant periods, shear wave velocity structures and information about sediment thickness or depth of engineering bed rock were evaluated based on data from boreholes, microtremor survey and laboratory results, combining with inversion program. The shear wave velocity of the top layer is Vs ≤ 190 m/s. The spectral amplitudes of the estimated strong ground motions were smaller at around 0.5 Hz and larger at around 3 Hz in Mandalay region. The peak ground acceleration becomes more than 0.8 g in some areas, which causes severe damage for buildings in high probability.