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DETERMINATION OF SAND MINING PROSPECTIVE ZONES BASED ON SEDIMENT THICKNESS ANALYSIS USING HVSR MICROTREMOR AND GRAVITY METHODS: A CASE STUDY IN CANGKRINGAN, SLEMAN, DAERAH ISTIMEWA YOGYAKARTA Sidik, Firdos Bahar; Ramadeo, Muhammad Gilang; Wulandari, Maria Diyah Ayu; Khumairo, Savira Zahrul; Nurkholijah, Ekasari; Pangestu, Farizki Budi; Fitrinova, ⁠Safina; Muhlisin, Haris
Journal of Scientech Research and Development Vol 6 No 1 (2024): JSRD, June 2024
Publisher : Ikatan Dosen Menulis

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.56670/jsrd.v6i1.272

Abstract

Mount Merapi is the most active type A volcano, especially on the island of Java. It produces sediment products totaling 140 million m3 located at the peak of Mount Merapi, descending through the mountain slopes to rivers originating from Mount Merapi. This sediment is subsequently utilized as a sand mining area. Therefore, it is necessary to determine prospect zones for sand mining that align with environmental, economic, and mitigation aspects in the Cangkringan area, Sleman, Yogyakarta Special Region. Seventeen microtremor measurement points were used with the Horizontal to Vertical Spectral Ratio (HVSR) method to determine sediment thickness, constituent lithology, and mining zones suitable for safety and mitigation aspects. Additionally, the gravity method was employed with 247 measurement stations obtained from GGM Plus to determine rock density and estimated thickness based on 2.5D modeling. The study resulted in the distribution of dominant soil frequencies ranging from 0.5 Hz to 7.5 Hz. High frequencies indicate old rocks, while medium frequencies suggest alluvial rocks with a thickness of ± 5 m. Low frequencies indicate alluvial rocks with a thickness exceeding ± 30 meters. Based on gravity results, the average depth is ±90-200 m with a density of 2.6 g/cm3, reflecting the depth of the bedrock in the study area, composed of andesitic volcanic rock. Soil vulnerability analysis in the study area classified into three categories, with values of 4.2-5.4 being highly vulnerable to surface deformation, values of 1.8-3.8 indicating moderate vulnerability, and values of -0.2-1.4 representing low vulnerability. Furthermore, the Peak Ground Acceleration (PGA) ranges from 500-1200 gal with intensity X. Ground Shaking Spectrum (GSS) data indicates that the study area experiences vibration phenomena with elastic soil dynamics. Therefore, the exploitation of sand resources in the Cangkringan area can be conducted in the southern region of Mount Merapi, approximately 2 km away from the mountain center. This is because the southern part of the research area has suitable mitigation measures. Moreover, based on the analysis, sediment thickness in this area ranges from ± 5-30 meters.
Microtremor-Based Mitigation Pathways and Disaster Post Placement in the Merapi Geotourism Area, Yogyakarta Fatihah, Kesya Lutfiany ; Wulandari, Maria Diyah Ayu; Pintrandhita, Anwar Said; Tarigan, Ryan Surya Dharma
Global Review of Tourism and Social Sciences Vol. 1 No. 2 (2025): Global Review of Tourism and Social Sciences
Publisher : Yayasan Ghalih Pelopor Pendidikan

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.53893/grtss.v1i2.353

Abstract

Cangkringan District, located on the slopes of Mount Merapi, is highly susceptible to volcanic and seismic activity, posing risks to its residents and the thriving geotourism sector. This study aims to determine optimal mitigation pathways and disaster post placements using geophysical methods, specifically the HVSR microtremor method and GGMPlus satellite gravity data. The research analyzed seismic vulnerability, ground acceleration, and shear wave velocity (Vs30), combined with gravity anomaly data, to identify high-risk areas and safe zones. The results produced a detailed mitigation map, guiding the placement of two disaster posts and evacuation routes based on soil vulnerability, topography, and rock density. These findings contribute to disaster risk reduction efforts and sustainable geotourism development by enhancing evacuation efficiency and safety for residents and tourists. This integrated approach offers a model for disaster-prone regions, balancing economic growth with safety and resilience against geological hazards