Statistical Analysis of the Effectiveness of Seawalls and Coastal Forests in Mitigating Tsunami Impacts in Iwate and Miyagi Prefectures

The Pacific coast of the Tohoku region of Japan experiences repeated tsunamis, with the most recent events having occurred in 1896, 1933, 1960, and 2011. These events have caused large loss of life and damage throughout the coastal region. There is uncertainty about the degree to which seawalls reduce deaths and building damage during tsunamis in Japan. On the one hand they provide physical protection against tsunamis as long as they are not overtopped and do not fail. On the other hand, the presence of a seawall may induce a false sense of security, encouraging additional development behind the seawall and reducing evacuation rates during an event. We analyze municipality-level and sub-municipality-level data on the impacts of the 1896, 1933, 1960, and 2011 tsunamis, finding that seawalls larger than 5 m in height generally have served a protective role in these past events, reducing both death rates and the damage rates of residential buildings. However, seawalls smaller than 5 m in height appear to have encouraged development in vulnerable areas and exacerbated damage. We also find that the extent of flooding is a critical factor in estimating both death rates and building damage rates, suggesting that additional measures, such as multiple lines of defense and elevating topography, may have significant benefits in reducing the impacts of tsunamis. Moreover, the area of coastal forests was found to be inversely related to death and destruction rates, indicating that forests either mitigated the impacts of these tsunamis, or displaced development that would otherwise have been damaged

Spatial Analysis of Earthquake Vulnerability Based on Geographic Information System (GIS) in Disaster Mitigation Efforts

Gempa bumi yang terjadi di selatan Tasikmalaya menimbulkan kerusakan cukup parah dibeberapa daerah, salah satunya adalah Kecamatan pangalengan di Kabupaten Bandung. Tujuan penelitian adalah mengidentifikasi dampak kerusakan, khusus bangunan akibat gempa dan mengidentifikasi faktor fisik dan sosial yang menimbulkan kerawanan wilayah Kecamatan Pangelangan. Metode penelitian adalah deskriptif kualitatif, data sekunder dari literatur yang terkait dengan permasalahan yang dikaji, berupa dokumen regulasi, hasil-hasil penelitian sebelumnya yang terkait dengan lokasi penelitian, interpretasi dan analisis peta geologi, peta rupa bumi, peta rawan gempa dan penggunaan lahan.  Hasil penelitian menunjukkan bahwa secara geologis kondisi fisik lahan daerah kecamatan Pangalengan rawan terhadap ancaman bencana gempa bumi. Berdasarkan penilaian kemampuan lahan termasuk lahan kurang stabil dengan tipologi kawasan rawan bencana gempa bumi tipe C terdapat lebih dari 2 faktor yang saling melemahkan. Jenis batuan dengan sifat fisik lemah, dekat dengan zona sesar, kemiringan lereng curam dan intensitas gempa tinggi. Selain kondisi lahan rawan secara geologis, faktor sosial turut memberikan andil terhadap tingkat kerusakan, yaitu kondisi rumah tidak ramah gempa, pola pemukiman mengelompok, tingkat kepadatan penduduk dan pengetahuan masyarakat tentang bencana yang masih kurang.The earthquake that occurred in the south of Tasikmalaya caused quite severe damage in several areas, one of which was the Pangalengan District in Bandung Regency. The purpose of this research is to identify the impact of damage, specifically buildings due to the earthquake and identify physical and social factors that cause vulnerability in Pangelang District. The research method is descriptive qualitative, secondary data from the literature related to the problem being examined, in the form of regulatory documents, the results of previous studies related to the research location, interpretation and analysis of geological maps, maps of the earth, maps of earthquakes and land use. The results showed that geologically the physical condition of the land in the Pangalengan sub-district was prone to the threat of an earthquake disaster. Based on the assessment of land capability, including unstable land with typology of earthquake-prone type C areas, there are more than 2 mutually damaging factors. Rock types with weak physical properties, close to fault zones, steep slope and high earthquake intensity. In addition to geologically vulnerable land conditions, social factors also contribute to the level of damage, namely the condition of houses that are not earthquake-friendly, settlement patterns are clustered, the level of population density and community knowledge about disasters is still lacking

Behaviour of buried water supply pipelines in earthquake zones

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