In conversation with Assistant Professor Aron Meltzner, Principal Investigator at the Earth Observatory of Singapore

1. How does the recent powerful magnitude-7.8 earthquake in Alaska remind us of similar hazards in Southeast Asia?

Last week, we saw a powerful earthquake off the coast of Alaska with a magnitude of 7.8 which had the potential to trigger a damaging tsunami, but fortunately this did not happen.

It occurred along a subduction zone where the Pacific Plate is subducting or slipping under the North American plate. The shaking that we know as an earthquake results from the sudden movement between these two plates, but that sudden movement also has the potential to lift up the seafloor, which in turns lifts the water above it, and that can cause a tsunami.

Whilst the tsunami this time was small, in 1964 there was a much bigger earthquake of magnitude-9.2 that produced a devastating tsunami that went across the Pacific Ocean and inundated communities across the Pacific Basin. 

East and Southeast Asia have also seen large tsunamis in recent years – in 2004 in the Indian Ocean, and in 2011 off the coast of Japan.  Both remind us how critically important it is to understand hazards in the region, where there are many low-lying countries and communities living close to sea level.

2. What connects sea level to active tectonics, and why is there a focus on both in the region of Southeast Asia?

My work is at the intersection of active tectonics in the earth and sea-level research. Like a detective, I use the geological record to decipher how both processes – tectonics and sea-level change – impact the coastline.

Think about it: if you were standing at the beach and sea level appeared to rise, could you honestly tell whether it was the sea surface that had risen or if the land had dropped instead? The geological record tells us such changes have happened many times in the past and my job is to figure out when, where, how much, and what caused the change.

We know that earthquakes and tectonic processes can move the land up or down, so if the land moved in the past, it might be a clue that an earthquake happened and that the region is prone to earthquakes. At the same time, we know sea level changes, and we need to better understand how sea level has changed in the past in order to better forecast how it might change in the future. It’s a complex problem.

3. How do geological records help you to form a view of past and future tectonic plate movement that had and will result in earthquakes and tsunamis?

Earthquakes on subduction zones – like the one last week in Alaska – cause the coastal region to move up or down. If the land moves up, relative sea level drops and the coastline moves seaward; if the land moves down, relative sea level rises and the ocean inundates the coastal region.

These changes leave permanent markers in the geological record, and if we can find those markers, we can use them as clues to changes that happened hundreds, thousands, or even hundreds of thousands of years ago.

The past is the key to the present – if an earthquake happened somewhere in the past, it can happen again in that place in the future. If we can figure out how often earthquakes have happened in a particular location in the past, we can get a better idea of how soon the next one might happen.

4. Why is it important to know what processes are driving sea-level rise in Southeast Asia?

Many different processes contribute to sea-level change. Each process contributes a different amount. Some processes might push sea level to rise some of the time and fall at other times; others might lead to long, steady changes at a constant rate over our lifetimes; still others might drive accelerating rates of sea-level change, as humans alter the climate more and more.

If we want to make the best possible estimates of the sea-level change we can expect in the decades ahead, we must better understand the effects of each potential contributor to sea-level change in the past so that we can better model how sea-level change will itself change in the future, and how it will be different from place to place. This, in turn, will allow us to help each community best prepare for the unique challenges that it faces.

There has never been a more important time to be an Earth scientist. Our work here at the Earth Observatory of Singapore has never been so critical to ensure we form a clear picture of the challenges that lie ahead, and the best solutions to mitigate these challenges to ensure all people in our region can live a happy and healthy life. 

_{(Source of thumbnail image: Yves Moret/Unsplash)}