The existence of nuclear installations in the Yogyakarta Nuclear Area is vulnerable to the eruption of Mount Merapi, the most active volcano in Indonesia. Tephra hazard has the potential to threaten the operational activities of nuclear installations in the Yogyakarta Nuclear Area; thus, it is necessary to analyze the distribution and potential hazard of volcanic ash from Mount Merapi for future eruptions. Numerical modelling is used in analyzing tephra distribution using TEPHRA2 software with parameters of the 2010 Mount Merapi eruption, which is then visualized to isomass and isopach maps of tephra distribution. The analysis resulted in the ash dispersion leading to the Yogyakarta Nuclear Area in April, May, June, and August with an accumulated mass of 20-50 kg/m3 with a thickness of 0.2-12 cm. It is necessary to deal with volcanic ash hazards such as roof strength, secondary cooling system, filtering system, and electrical system for several installations in the Yogyakarta Nuclear Area.
Background: DIY is a province in Indonesia that is very susceptible to earthquakes. In 2006, a seismic event measuring 6.2 on the moment magnitude scale struck DIY, causing injuries and extensive damage to both the structural and non-structural elements of several buildings, including one in the education sector. The problem of structural damage to educational facilities is a significant worry, especially in school communities that cater to vulnerable children, such as those in special needs schools (SLB), who are more susceptible to harm during disasters. This study aims to assess the level of preparedness and accessibility of the special needs school community located in a very high seismic region of earthquakes in the DIY, in the event of an earthquake. Methods: The structural assessment took the form of a binary question, requiring a simple yes or no response. Findings: To reduce the risk of earthquakes in the special needs education sector, a review of the preparedness of the special needs school building and community was carried out by implementing “Satuan Pendidikan Aman Bencana (SPAB)” or Disaster Safe Education Unit guidelines. The findings suggest that SLB Sekar Melati Muh. Imogiri (78,26) was classed as having moderate earthquake risk, whereas SLB Dharma Bhakti Piyungan (88,55), SLB Insan Mandiri Dlingo (90,29), and SLB Purworaharjo (88,41) featured infrastructure that was rated as very vulnerable. With respect to SLB Dharma Bhakti Piyungan (64,52), SLB Insan Mandiri Dlingo (60,11), and SLB Purworaharjo (76,94), their average community readiness index scores put them in the intermediate capability category for earthquake preparedness. SLB Sekar Melati Muhmmadiyah Imogiri, however, was categorized as having a low capacity for earthquake readiness with an average index score of 56,92 for community preparedness. Conclusion: special needs school communities should raise their level of preparedness by undertaking seismic socialization and regular simulations to boost the community's understanding of earthquakes and reduce the likelihood of harm following an earthquake. Novelty/Originality of this Study: The study breaks new ground by assessing earthquake preparedness and accessibility in special needs schools within a high-seismicity region, addressing a critical gap in disaster risk reduction for vulnerable populations.
The 7.5 Mw tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction that triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. Extensive damages to infrastructures occurred as the result of these earthquake-triggered disasters. This study explores the causing factors of the massive mudflow in Balaroa, Petobo, and Jono Oge areas as it is a quite rare phenomenon. This study focuses on the causing factors of liquefaction such as the condition of soil lithology, depth of water table, distance to the fo1cal mechanism, and the thickness of soft sediment.
On May 27 th 2006, Yogyakarta earthquake happened with 6.3 Mw. It was causing widespread destruction and loss of life and property. The average shear wave velocity to 30 m (Vs30) is useful parameter for classifying sites to predict their potential to amplify seismic shaking (Boore, 2004) [1]. Shear wave velocity is one of the most influential factors of the ground motion. The average shear wave velocity for the top 30 m of soil is referred to as Vs30. In this study, the Vs30 values were calculated by using multichannel analysis of surface waves (MASW) method. The Multichannel Analysis of Surface Waves (MASW) method was introduced by Park et al. (1999). Multi-channel Analysis of Surface Waves (MASW) is non-invasive method of estimating the shear-wave velocity profile. It utilizes the dispersive properties of Rayleigh waves for imaging the subsurface layers. MASW surveys can be divided into active and passive surveys. In active MASW method, surface waves can be easily generated by an impulsive source like a hammer, sledge hammer, weight drops, accelerated weight drops and explosive. Seismic measurements were carried out 44 locations in Yogyakarta province, in Indonesia. The dispersion data of the recorded Rayleigh waves were processed by using Seisimager software to obtain shear wave velocity profiles of the studied area. The average shear wave velocities of the soil obtained are ranging from 200 ms-1 to 988 ms-1, respectively.
Abstract The 7.5 M w tectonic earthquake that hit Palu City on 28 September 2018 was followed by tsunami and liquefaction, triggered massive mudflows in Balaroa, Petobo, and Jono Oge areas. This study focuses on the generating factors of liquefaction such as the condition of soil lithology, depth of water table, the distance to the focal mechanism, and the thickness of soft sediment. Microtremor data, including the Horizontal Vertical Spectral Ratio (HVSR), geological condition, and borehole data, were examined to conduct the liquefaction analysis. The analysis results based on the microtremor data showed that the distribution of ground shear strain values in Palu City ranged from 0.75 × 10 –4 to 2.56 × 10 –4 . The distribution of the locations of the liquefaction was correlated to the distribution of ground shear strain values. High ground shear strain values and a shallow groundwater level were discovered in Palu City valley, which indicates that liquefaction in Palu City will undoubtedly occur. The semi-empirical method confirmed that Balaroa, Petobo, and Jono Oge had undergone large-scale liquefaction at a maximum depth of 16 m below the ground level. The average peak of water runoff that generated the mudflow was estimated to be at 11.31 cm 3 /s. Since the soil has loose soil grain with high water content, the soil will turn into a massive amount of mud during the liquefaction.
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