Uproar Over Tsunami Threats

Kompas/Didie SW

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After last week’s news on the 8.0 megathrust earthquake threat in Jakarta, news about the threat of potential tsunamis to the south of West Java and the Sunda Strait also went viral and received a wide variety of opinions, responses and refutations.

A discourse that focused only on the potential issue of dangerous threats was taken by the public as a disturbing polemic because it was not accompanied by measurable and applicable solutions for mitigation. Moreover, the current issue has developed in a far distance direction from the realm of science, which was the original entrance to the discussion. If such a pattern in disaster discourses continues, it is feared that the long-term goals to improve the public\'s real resilience will not be achieved, because such public discourse stop merely at the mere mention of the threat of danger and are always devoid of comprehensive information on what to do next.

Tsunami in Sunda Strait

Actually there is nothing new in the information of a potential tsunami in the Sunda Strait that could reach a height of 57 meters. Looking back to 1883, the eruption of Mount Krakatau triggered a tsunami with a height of 37-45 meters in Merak and 22 meters in Betong Bay (Bandarlampung today). The power of the Krakatau tsunami is still visible in the boulder of an estimated 600 tons, which was carried on the tsunami to the coastal region of Anyer. The 1883 tsunami killed up to 36,417 people.

As written in Symons\' notes (1888) in Choi et al. (2003) and Pelinovsky et al. (2005), the magnitude of the 1883 tsunami provoked "unusual oscillating waves" in places as far away as South Africa’s Port Elizabeth, where tidal devices recorded waves of 1.58 meters or Aden-Yemen (37 meters) and the English Channel (up to 6 meters). Therefore, the coastal area of the Sunda Strait is a region that has encountered giant tsunamis in its past.

The earthquake in the Italian city of L\'Aquila can be used as a lesson in interpreting the role of researchers and their researches in developing disaster preparedness. The earthquake that struck on Apr. 6, 2009 destroyed 3,000 to 11,000 buildings and left 309 people dead.

The earthquake came to the world’s attention because in 2012, six Italian government officials (who were also scientists) were jailed for 6 years on charges of "murder without intent" for giving "inexact, incomplete and contradictory information" about potential earthquakes.

A month before the 2009 earthquake, a television show reported that a technician discovered an increase in radon gas at the site where the earthquake would hit, a gas byproduct of natural radioactive decay which, according to several scientific studies, could be a sign of a possible earthquake – although the increase in radon gas emissions is not always consistent with an earthquake’s occurrence.

The technician was later accused of spreading false news and reported to the police on charges of "spreading fear" among the public, and was ordered to remove all his analyses of potential earthquakes from the internet. Several days before the Apr. 6 earthquake struck, an increase in the occurrence of small tremors in L\'Aquila was detected, and the people started becoming anxious over the earlier news that a major earthquake might possibly happen.

To calm the public, several scientists and government officials made statements that the predicted quake "seemed unlikely" and "the situation remained secure" and small earthquakes were "common geological phenomena", because scientifically, there no reliable method yet existed to predict when an earthquake would happen.

However, what can I say, but the very people who were asked to remain calm were later hit by a devastating earthquake that razed their city. Regardless of the mistakes in the statements, many parties mentioned that the L\'Aquila disaster had occurred due to the quality of the buildings, which had not been designed to withstand earthquakes. However, the scientists and government officials who issued statements that no earthquake would occur were still tried, even if their sentences were annulled two years later in 2014.

The L\'Aquila event can be taken as a lesson that information about a potential local disaster is not to be debated or contested, but to be followed up with appropriate mitigation efforts. Such follow-up efforts must also be accelerated because disaster will not wait; it is we who must prepare immediately to minimize the impacts from such disasters.

Mitigation solution

In preparing earthquake and tsunami mitigation efforts, two characteristics of disasters must be considered, high frequency with relatively low to medium risk and low frequency but with high risk.

Earthquakes of the first kind are the most likely and historically the most common cause of tsunamis in the region. Disasters of this type usually recur within relatively short recurrence intervals of 50 to 150 years, with tsunamis of less than 10 meters high. Disasters of the second characteristic are worst-case scenarios that may occur every 400 years with tsunamis of an estimated 20 meters or higher (Muhari et al., 2015).

Article 17, Paragraph 1 of Government Regulation No. 64/2010 on Disaster Mitigation on Coasts and Small Islands states that mitigating high-risk disasters are to focus on nonstructural/non-physical measures.

Why? Because the 2011 earthquake and tsunami Japan in provided very important lessons that no physical structure would be able to withstand a tsunami over 20 meters high. Moreover, it should be remembered that no physical structures, even those with concrete frames, are more than 50 years old. Meanwhile, when we talk about massive tsunamis, we are speaking of a recurrence interval of over 400 years. That is, when such a tsunami occurs, the tsunami-resistant structures may already be in a condition unsuited to reducing potential impacts.

Then what kinds of nonstructural efforts can be taken in high-risk disasters? It must start with mitigation planning for coastal areas. After the 2011 tsunami, Japan divided its coastal areas into two types: areas that are almost always affected by tsunamis up to 1 kilometer from the shoreline with a recurrence interval of 30-150 years, and areas affected by tsunamis up to 3 kilometers from the shoreline with a recurrence interval of more than 200 years.

These two areas should not have human settlements. The first area should be used only for tourism and conservation. The second area may be utilized by industry and agriculture, with buildings that must be able to withstand very powerful earthquakes and tsunamis. Disaster evacuation plans and facilities in the event of a tsunami should also be made available and accessible to those in the area.

Disaster education and evacuation drills supported by affordable infrastructure were essential in coastal areas with dense human settlements that had never experienced a tsunami. Japan conducts evacuation drills at least three times a year in every city at risk of tsunami. Then, to protect economic assets such as buildings and infrastructure in tsunami-risk areas, the role of property insurance in risk management cannot be neglected.

National regulations on disaster insurance are urgently needed. Without such regulations, disaster insurance schemes are difficult to realize in Indonesia. For low- to medium-risk disasters, Article 17, Paragraphs 2 and 3 of Government Regulation No. 64/2010 state that the function of physical structures in disaster mitigation can be enhanced through nonphysical measures. This is intended so that physical structures such as coastal forests, embankments and breakwaters can be developed in line with efforts to change people\'s behavior in responding to signs of danger such as early warning systems, natural phenomena and others.

Finally, we must all agree that information on a disaster should be understood in the broader context of increasing our readiness. The results of research may be debated; appeals to maintain public calm and vigilance may be made. However, these should be accompanied by more urgent measures, namely the implementation of both structural and nonstructural disaster mitigation efforts that have been planned well and disseminated for sustainable public awareness.

Abdul Muhari, Chairman, Sentinel Asia Tsunami Working Group