Based on the numerical simulations, it is found that the shortest tsunami estimated arrival times, as shown in Fig. 5. The shortest ETAs were mostly due to a tsunami generated from the largest earthquake magnitudes from the Tanimbar Trough (southeast of the Banda Arc). Here, the ETAs are between 37 and 57 minutes. With these, the community along the bay are estimated to have sufficient time to evacuate themselves to higher ground, provided that the community will respond swiftly after the earthquake. As the bay is surrounded by many higher ground places within 500 m from the coastline, the community will be able to evacuate timely if the city traffic can be managed properly. The shortest ETA is located around South Leitimur, to the east direction of the Ambon Bay Area. At this point, the shortest ETA could reach about 37 minutes after the earthquake. In this area, the population number is smaller compared to other sub-districts in Ambon City.
The largest inundation area based on the deterministic simulations was found based on the Tanimbar Trough scenario, as can be seen in Fig. 6. The highest inundation was found around the narrow strait that connects the outer part of the bay to the inner part of the bay. This is also the location of Merah Putih bridge that connects both sides of the bay, as aforementioned. Another area that could have severe tsunami impacts is located in the middle of the Baguala sub-district, named Passo. This area has been recently assigned as the new area of the government offices complex. Passo has a large flat area unlike other parts of the city which are limited by steep ground. Based on the largest simulated scenario, the Pattimura Airport is projected to be free from the tsunami. Nevertheless, some areas near its coasts will be inundated by the tsunami by ~ 2.0 m of tsunami flow depth. Based on the simulations, we could identify that there will be three areas around the Ambon Bay Area that will be severely impacted by the anticipated tsunamis, namely Baguala, Sirimau, and Teluk Ambon sub-districts. A more concerning issue is that these three areas are where main populations of the city live and are the main economy centers of the Province of Maluku.
Tsunami Evacuation Readiness of Ambon City’s community
A total of 300 survey participants were community from Leitimur Selatan (n = 58, 19.33%), Nusaniwe (n = 125, 41.66%), Sirimau (n = 56, 18.66%), Baguala (n = 44, 14.66%), Teluk Ambon (n = 17, 5.66%). Of all the respondents, 46.33% were male and 53.66% were female. The respondent's most recent educational background were never attended school (0.33%), not completed elementary school (3%), elementary school graduate (19.66%), middle school graduate (15%), high school graduate (52.33%), academy/university graduate (9.66%). The majority of respondents are currently employed (49.33%) and housewives (30%), while the remaining individuals are unemployed/ not seeking jobs (3.33%), and actively seeking employment (2.66%). The majority of respondents (81.33%) live within a distance of 500 meters from the shoreline, while the remainder reside beyond the 500-meter mark.
One of the important factors in tsunami evacuation readiness is community awareness and understanding of the early signs of a tsunami. As seen in Fig. 7, most of the respondents (81.67%) indicated that an earthquake which causes strong shaking thus rendering people unable to stand is one of the signs of a tsunami. This result indicates that the community in Ambon City already have a good understanding of the relationship between an earthquake and a tsunami. Furthermore, 68.67% of respondents considered the seawater that suddenly receded as a sign of a tsunami. They realized that when the sea water retreats abnormally, it could indicate a tsunami threat. This response reflects a good knowledge of observing natural changes such as receding sea levels. However, tsunamis that occur due to earthquakes are not always marked by receding sea water. The community should not go to the coast to observe the sea level after a big earthquake because a tsunami can occur without the sea level receding beforehand. There is a need for further educate the community about the correct signs of a tsunami. Educational efforts can be focused on the signs of a tsunami providing information about appropriate behavior when these signs occur. Increased public awareness of tsunami signs can reduce the level of vulnerability and increase the level of safety in facing the tsunami hazard.
This study also examines the sources of tsunami information that the community has accessed. The most accessed sources of information are relatives, friends, or neighbors (89.67%). These results indicate that interpersonal communication in a social environment is one of the important and reliable sources of information for the community. Direct and well-understood communication with those other individuals closest to them enables the dissemination of tsunami knowledge. The survey results also show at respondents received information about the tsunami through television (89.33%) and internet/social media (67%), which are both important mediums in the digital era that can reach many people relatively quickly. These results show the importance of television and internet/social media as an effective information channel in conveying knowledge about the tsunami to the public. The research results also reveal various other sources of information the community uses in obtaining knowledge related to the tsunami (see Fig. 8). This result shows that these sources still contribute to disseminating knowledge about tsunamis. Therefore, a holistic approach involving various media and institutions can effectively raise public awareness about the tsunami hazard.
Furthermore, the survey results show that only 4% of respondents know about local traditions and wisdom related to the tsunami. These results indicate that efforts are needed to increase community understanding of local knowledge that can help deal with the tsunami hazard. Up to 50% of respondents had discussed with or informed family members about the tsunami. Hence, there is a need for a more comprehensive education campaign and encouragement to have more discussions and information sharing about the tsunami within the family, in order to build a better-prepared community more capable of dealing with tsunami hazards (Dudley et al. 2011; Lindell et al. 2015).
Regarding the respondents’ efforts to anticipate the tsunami hazard (Fig. 9), most respondents (69.33%) were aware of the tsunami hazard around them. Almost all respondents (95.33%) had prepared to provide clothing, cash, and special family needs. The survey results also underscore that some respondents (43%) have conducted tsunami mitigation efforts (such as planting mangroves, etc.). Preparations involving evacuation planning, such as identifying assembly points, evacuation plans, and practicing with the family, still need to be improved, with response rates ranging from 37-57.33%. Only around 24–49% of respondents have prepared important documents, ready-to-eat food that is durable, and first aid kits and particular medicines. More intensive efforts are needed to educate the community about the hazard and mitigation measures that can be taken to improve preparation for the tsunami hazard. A socializing methodology to convey the importance of more comprehensive evacuation planning and emergency preparation is also necessary (Latcharote et al. 2018; Carvajal et al. 2019).
The survey results highlight that around 41.33% of respondents have attended workshops or socialization efforts on tsunami mitigation. Around 16% of respondents have attended a first aid training course. However, only 20% of the respondents had participated in the evacuation drill. These results reveal low community participation in tsunami-related training and drill activities. Therefore, authorities, related institutions, and local communities need to work together to increase community participation through systematic, structured, and sustainable outreach, workshops, training, and evacuation drills in order to strengthen preparedness towards tsunamis.
In terms of tsunami early warning, only a few respondents knew of traditional methods passed down from generation to generation in the community as tsunami early warning (3.33%), and were aware of local agreements regarding tsunami early warning (5.67%). More extensive and intensive educational efforts are needed to expand knowledge about traditional ways, local agreements, and early warning systems in dealing with the tsunami threat. The level of community knowledge about the existence of an early warning system for tsunamis is higher (35.67%) than knowledge about traditional methods or local agreements. Moreover, the survey responses suggest that local governments (71.67%) and places of worship (74.67%) have a significant role in providing early warning information to the public. Community figures, folklore, generations, and personal experience (64.33%) also play an important role in disseminating this information. However, efforts are still needed to increase community understanding and preparedness related to the existing early warning system, and allow the community to take appropriate actions and improve safety during a disaster (Lauterjung et al. 2010; Yuzal et al. 2017; Núñez et al. 2022).
This study also examines the accessibility of the community to several important necessities in an emergency. The survey results indicate that some respondents (33.33%) have access to information on preparedness and emergencies. In addition, respondents stated that they have access to communication tools during a crisis (54.33%), transportation for evacuation (40.33%), and health facilities (44%). These results recommend that there is a need to increase the availability of transportation that can be used for evacuation, especially in disaster-prone areas. In addition, the government and other related parties must increase access to information on preparedness and emergencies, communication tools, and health facilities (Güerena-Burgueño et al. 2006; Rizal et al. 2020).