A Preliminary Study on Tsunami Disaster in Yogyakarta: Identification of Vulnerability Order and Components

A tsunami is a disaster that can be hardly estimated. It is a significant concern UN since more than 60% of the world's population lives in coastal areas prone to tsunamis, including Indonesia. The county community with complex and dynamic plate requires mastering of mitigation strategies as a tsunami preventive effort. Understanding the vulnerable elements in risky areas is critical. However, the magnitude of potential disasters cannot be minimized. This study analyzes the tsunami vulnerability in Bantul, Special Region of Yogyakarta (DIY). The analysis was based on a description of assessment parameters such as land use, the physical condition of the area, social conditions, and availability of infrastructure. The results show that social vulnerability had the most significant impact.


Introduction
A tsunami refers to waves that are faster, taller, and stronger than wind or storm surge (Chen & Cheng, 2016;Rangel-Buitrago et al., 2020). It has frequently occurred in the last decade, damaging coastal structures (Nandasena et al., 2012). Its incidencet on a large scale is relatively less frequent compared to hydrometeorological disasters.The associated waves are unpredictable because they are caused by sudden significant volcanic displacements, initially triggered by earthquakes, landslides, volcanic eruptions, or meteors (Al-Faesly et al., destruction of property in more than ten countries bordering the Indian Ocean (Grilli 2007, Leonard & Lucinda, 2014Iverson & Prasad, 2007;Roshan et al., 2016). On February 27, 2010, a tsunami disaster was triggered by an 8.8 magnitude earthquake of the coast of Chile.
The waves reached local run-ups of 29 meters high on coastal cliffs (Fritz, 2010). On March 11, 2011, a magnitude 9.0 earthquake stroked near the coast of northeastern Japan and swept along the coast, penetrating the land with a maximum height of 40 meters (Yeh et al., 2013).
On September 16, 2015, an 8.3 magnitude earthquake occurred off Chile's central coast and triggered a tsunami with a maximum runoff height of 13 meters (Contreras-Lopez et al., 2016). In Thailand, the dock plates at the port of Khao Lak and the fishing port of the Ban Nam Kem deck were severely damaged by the uplifted pressure due to the Indian Ocean tsunami of 2004 (Ghobarah et al., 2006). The same incident occurred in Japan and damaged the Sendai port in the Tohoku region during the 2011 tsunami (Suppasri, 2012). The implementation of spatial planning should be carried out comprehensively, holistically, well-coordinated, integrated, effective, and efficient, focusing on political, economic, social, culture, defense, security, and environmental sustainability (Ibrahim & Hegazy, 2013). Spatial planning needs to be based on the system approach, main function, administration, activity, and strategic value areas, taking into account the disaster factor (Muta'ali, 2014). The development plan of the southern coastal region, including the Bantul area, has encouraged unity in the spatial planning following the risk of the tsunami disaster (Balasundareshwaran et al., 2020). This study analyzes the tsunami vulnerability orderbased on the assessment parameters, including land use, the physical condition, social state,and infrastructure availability.

Methods
The identification of dangerous elements in the disaster-prone area is part of mitigation. This aspect was investigated by Tanaka

Results and Discussion
Indonesia is a country prone to the tsunamis, especially in the coastal area that   (2008 ) The greatest tsunami in the history of Indonesia occurred in Aceh on December 26, 2004. It started by the earthquake magnitude of 9.3 SR, which caused a strong shock and fault, stretching from Aceh to Andaman. The tsunami was attributed to the earthquake with huge losses and 250,000 deaths (Mardiatno, 2008). Almost all of the tsunami disasters led to material losses and claimed many lives. According to Table 2.1, the most recent tsunami occurred in October 25 th 2010 in Mentawai Island, West Sumatra. It started with an earthquake of magnitude 7.7 SR, followed by tsunami waves of 3-10 meters. This caused destruction of 77 villages and more than 400 deaths (Mardiatno, 2008).
Bantul Regency has ahigh vulnerability because it directly faces the Indian Ocean.
Additionally, the coastal typology tends to be flat (Trihatmoko, 2017;McGuire, 2020). When a tsunami strikes, it is likely to damage the physical and social aspects, as well as the existing infrastructure.
Social vulnerability should be the first concern since it relates to the number of people affected (Koroglu et al., 2019;Liu et al., 2020;Malherbe et al., 2020). The readiness of every resident in the face of disasters significantly affects vulnerability. In case the community is ready to face any disaster, the severity can be reduced.
Lina Wahyuni et al / GEOSI Vol 5 No 2 (2020) 186-195 Social vulnerability is the ability to recover from the impact of natural disasters based on age and sex group of the populations (Dawyer, 2004. in Zulkarnaen, 2012. It is based on the understanding of the disaster and the resulting conditions. This includes the ability to evaluate when it occurs and the recovery process. The population of women, children, and the elderly is considered the most vulnerable (Subarkah, 2009).  Table 2 shows the population in Bantul Regency, which can be potentially affected in case the tsunami strikes. This data includes the number of people living in the district directly facing the Indian Ocean. Population density also affects the vulnerability of a region. Table 2 shows the Pandak District has the highest population and density.  (2016) Economic vulnerability is the risk of damage, negative impact, or external shock resistance due to unexpected events (Koroglu et al., 2019;Liu et al., 2020). The calculation losses can be a good indicator of the economy (Gulllaumom, 1999, in Zulkarnain 2012. Physical vulnerability is the last aspect describing the extent of damage to physical infrastructures exposed to hazards, such as residential buildings (Ishtiaque et al., 2019). It affects the local community's structural readiness and the condition of structures (Prasstiya, Lina Wahyuni et al / GEOSI Vol 5 No 2 (2020) 186-195 2013. The main Physical vulnerability in Bantul Regency include JJLS and the existence of Airport .
The most important thing to do in adjusting the development of risk management strategies is to assess vulnerability to potential tsunami damage in the proper order (Lantz et al., 2020). However, vulnerability assessment has never been formulated in an appropriate legal document. Building vulnerability means calculating thestructures' capacity in the horizontal pressure of tsunami flows and its susceptibility to water (Dall'Osso et al., 2009;Koroglu et al., 2019).

Conclusion
In this study, the ranking of the element at risk involves social, economic, and physical vulnerabilities. Social vulnerability is considered to be the most powerful aspect associated with detailed and varied subcomponents. The economic vulnerability comes second in terms of the economic conditions of a society. It is closely related tocommunities'specific capacity to survive. Physical vulnerability is rated last since rebuilding of infrastructures is easier than social or economic development.

Conflict of Interest
The authors declare that there is no conflict of interest with any financial, personal, or other relationships with other people or organizations related to the material discussed in the article.