"On this paper the lead author is Koran Junk from Thailand, her colleagues Montry in Turku, Brian and myself from the US, Yoki SoWa from Japan, Namy Padergrass from Australia. We go out to these beach-ridge swales, these low water areas and we dig holes and see what we found. We didn't find anything and so we moved to the next area, dig holes again and try again. And finally we went to a place with the large wet swale and when we dug there, we found the 2004 deposit well preserved and a layer below it. And as we worked towards the wettest part of the swale, we found more and more layers and we ended up finding at least three other layers besides 2004 in this area."

 

Here on the island of Phra Thong, the top level is sand deposited in 2004. Carbon dating reveals layers in this marsh going back 2,800 years, and the most recently historical times dates from about 700 years ago.

 

"How do we know that the sand came from the sea, ok, At Phra Thong Island? How do we know it's not a river flood? Well, the island is a beach ridge plain. There are no rivers. There is no way that a river from the upland can ever get there. And so just by context, the only place the sand could have come from is the sea, unless it was blown there by wind, but the island is delicately striped by the berms of the former beaches. There are dozens and dozens of these beautifully preserved, they haven't been overprinted by the landforms of windblown sand."

 

"Sand layer we found in these parts in Aceh started off very coarse close to the ocean and got finer as you go inland. So as the wave comes in that is a very turbulent wave board coming in. As it slows down, it drops out the heaviest grits first and soon it wipes the fine grits that continue to move inland."

 

Working with Bryan in Aceh Sumatra, Katrin Monecke led an international team which not only found sand layers matching as in Thailand, but also found evidence of a slightly smaller tsunami which hit the country in 1907. But in one place most people actually survived the wave in 2004, why?

 

"Do they have the story about the 1907? ""Yeah."

 

"This is a small island off the coast of Sumatra called Simeulue Island. And the people there were strongly affected by the earthquake that occurred in 1907, and this event to write out the significant part of the population as recorded by stories in memory of these people."

 

The stories of that 1907 tsunami have been passed down through several generations.

 

"So when the earthquake occurred in 2004, they knew how to react. They actually went to preordained meeting places; they ran high ground for the tsunami arrival. Only 8 people out of the population almost 90,000 died during the 2004 tsunami."

 

So, education is key. The Thailand team found a way to communicate their findings in a telling way. 

 

"We were already scheduled to meet with a group of people in the nearby village to tell them why we were there. We scrunched up a piece of corrugated steel roofing from a building that had been destroyed by the tsunami, and pressed it against the wall of the pit and cut the thing out and propped it down to the ground and cleaned it up, loaded it down to the tractor for the two kilometer bumpy ride back to this *** meeting and then laid it out on the table and showed people, ok, here is a record of 2004. You all know about this, because most of them had probably lost family members too and then over here just down below it was sign of an earlier one. "

 

2004 was really a watershed event because it was so unprecedented in scale, I mean, almost a quarter of million people died in that event. It really was a wake-up call for whether this could occur in other places. Probably the biggest earthquake that can occur would occur offshore or again in Washington or Cascadia subduction zone and would probably be on the order for magnitude 9 to 9.5 earthquake.

 

Yeah, we are guessing maybe a hundred and fifty kilometers from tsunami source for a Cascadia tsunami if it's generated directly off Strait ***, maybe 150 kilometers from there to here.

 

But there is 80 muzzle of the coast.

 

Everybody along here had a tsunami break. 

 

Really? 

 

But from this intervale, you wouldn’t be surprised to see another big Cascadia earthquake happen tomorrow. 

 

Anything that we as emergency managers can gain from these studies to pass on to the folks that live along the beaches here and have settled in the northwest. It’s certain that's concrete and tangible. If you follow my signs, you are gonna get a diagram, aren't you?