On the 28th of September 2018, a massive earthquake struck the region Sulawesi in Indonesia. The moments before this event, the region experienced many foreshocks with high magnitudes. The earthquake had a magnitude of 7.5 on the scale of Richter and created a tsunami. These two natural disasters took the lives of 2,256 people and 10,679 were injured. Most of these people died as a result of the tsunami, mainly because they did not know it was coming. Some people were still partying at the beach, when the tsunami hit the coast. The tsunami-warning systems failed.

This leaves us with the following questions: “how could these systems fail?” and “how can this be prevented in the future?”

How could these systems fail? Indonesia’s tsunami detecting system consists of seismographic sensors, buoys and tidal gauges. None of these components worked correctly. We will go through them one by one.

The seismographic sensors did detect the tsunami. A warning was send through text
predicting a tsunami of 1.6 to 9.8 feet and telling people to evacuate. However, this warning never reached anyone because the earthquake took out all the cell phone towers. There were also no sirens along the beach.

The buoys float in the sea and detect changes in sea level. When the sea level changes very quickly a signal is send to the national meteorological agency, which in turn warns the local authorities. This did not happen because none of the buoys were operational. They were all already broken for years, because of vandalism and lack of maintenance.

The tidal gauges are located at the shore and measure the change in sea level every 15 minutes. This information is send to the national meteorological agency. This system failed because no significant rise in sea level was measured. This particular tsunami happened very fast after the earthquake, making the 15 minutes intervals
too big for the tidal gauge to measure the sea level rise effectively. How can this be prevented in the future?

One of the ways this can be prevented in the future is by having a different type of warning system linked to the seismographic sensors. Just receiving a text is tricky, since people do not always have their phones with them and you rely heavily on the cell phone towers working. An alternative possibility is having more alarm sirens at the beach but also further into the country. Next to this, the whole system should be upgraded or replaced. It seems unacceptable that the buoys were already broken for years. The problem is that Indonesia does not have the money to fix the tsunami warning system. They will need financial aid from other countries to be able to replace the current broken system. Another way to prevent deaths is by informing the citizens that if the earthquake causes shaking for longer 20 seconds, the change of a tsunami hitting is high. So, when this happens they should always go to higher
ground. This can possibly be a very effective and low-cost method.

To conclude we can say that the tsunami has such severe consequences because the
systems in place are not working correctly and for something like this to never happen again the current systems should be replaced or fixed.

This Girugten article first appeared in GEO PROMOTION MAGAZINE, 23rd of February, 2019.

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