Mamuaya, Gybert E.
Universitas Muhammadiyah Surakarta

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Land Subsidence Analysis of Reclaimed Land using Time-Lapse Microgravity Anomaly in Manado, Indonesia Wibowo, Sandy Nur Eko; Mamuaya, Gybert E.; Djamaluddin, Rignolda
Forum Geografi Vol 32, No 1 (2018): July 2018
Publisher : Universitas Muhammadiyah Surakarta

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.23917/forgeo.v32i1.5882

Abstract

Coastal area land reclamation is a policy with various benefits, including its potential to increase economic growth. However, reclamation also potentially has adverse impacts on the environment, including increasing pressure on biodiversity, natural resources and natural ecosystems, and the most common problem is land subsidence. This study uses time-lapse microgravity anomaly to ascertain the distribution of gravity and vertical gradient anomaly in order to map the subsidence characteristics occurring in the Manado reclamation area. From the research that has been previously conducted, the positive gravity anomaly is spread around Megamall-Multimart to the north of Monaco Bay and on the southern side of Manado Town Square (Mantos). Positive anomaly values range from 3 to 29.7 μGal. The negative anomaly values are scattered around the Mantos and Megamas separating bridge and at some points around the Whiz Prime Hotel, Menora Church and towards the Pohon Kasih Megamas area. The reclaimed areas generally experience subsidence accompanied by a reduction in groundwater mass (Megamall and Mantos) due to the use of the groundwater by the community in these areas. Uplifts also occur at some points in the reclamation area of Megamas as a result of the occurrence of land subsidence. Longer-term research is needed to determine whether there is an increase in the rate of land subsidence in the Manado reclamation area. Over a longer period of time it can also be established whether there are other factors which affect land subsidence. Other geodetic methods to monitor subsidence, such as levelling, InSAR and GPS survey, which have been conducted in other locations, are also needed to obtain more detailed information about the land subsidence in this area.
ANALISIS POTENSI RAMBATAN TSUNAMI DI PANTAI UTARA DESA DULUKAPA DAN DEME 1 KABUPATEN GORONTALO UTARA UNTUK MITIGASI BENCANA TSUNAMI Nurfitriani, Nurfitriani; Mamuaya, Gybert E.; Djamaluddin, Rignolda; Yatimantoro, Tatok
MAJALAH ILMIAH GLOBE Vol 20, No 2 (2018)
Publisher : Badan Informasi Geospasial

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (1426.346 KB) | DOI: 10.24895/MIG.2018.20-2.767

Abstract

Secara tektonik, zona subduksi di utara Gorontalo berpotensi menimbulkan gempa bumi yang dapat mengakibatkan tsunami. Kajian statistik seismisitas menunjukkan adanya indikasi celah kegempaan di wilayah tersebut dengan Magnitudo maksimum sebesar 8,2 Mw. Pemodelan tsunami dilakukan untuk mengestimasi ketinggian run up tsunami di pesisir pantai dan luasan daerah genangan tsunami sebagai upaya mitigasi bencana tsunami di Desa Dulukapa dan Deme 1. Pemodelan tsunami menggunakan teori gelombang linier di laut dalam dan gelombang perairan dangkal pada perairan dengan kedalaman dangkal dan daerah landaan dengan grid yang konstan dengan bantuan aplikasi TUNAMI-N2. Gempa bumi yang digunakan untuk pemodelan merupakan skenario terburuk berdasarkan tatanan tektonik dan sejarah kegempaan wilayah penelitian. Data yang digunakan meliputi data batimetri GEBCO (General Bathymetric Chart Of The Ocean) grid 30 arc second dan topografi SRTM (Shuttle Radar Topography Mission) grid 1 arc second yang dikeluarkan oleh USGS. Selanjutnya, data gempa bumi dan tsunami masing-masing diperoleh dari katalog gempa bumi Advanced Nasional Seismic System (ANSS) dan Badan Meteorologi Klimatologi dan Geofisika (BMKG). Hasil penelitian menunjukkan waktu penjalaran gelombang dari episenter ke pantai utara Desa Dulukapa 18,2–13,8 menit dengan run up 9,8–13,8 m dan jarak terjauh landaan tsunami sejauh 800 m. Sementara itu, waktu tiba tsunami di Desa Deme 1 sekitar 18,8–23,83 menit dengan run up 10,76–15,1 m, dan jarak terjauh landaan tsunami sejauh 830 m. Luasan daerah landaan tsunami mencapai 1900 m² pada kedua desa tersebut. Kedua desa tersebut merupakan wilayah yang rawan terdampak tsunami sehingga perlu dilakukan upaya mitigasi bahaya tsunami untuk mengurangi resiko yang ditimbulkan.