Armed with ordinary shovels, World War II entrenching tools, and Japanese weeders,
Saidul Alam and Wanna Phyo and their AIT faculty advisor dig trenches tens of meters long. The trenches expose the tsunami sand sheet -- often tens of centimeters in thickness -- down into the previous topsoil. The students then scrutinize structural features in the sand layers often at millimeter scale. They also take samples for laboratory analyses, and they take “fingerprints” of the sand layer column by applying glue to harden the sands and take a “skin peel” of the trench wall.
The students received scientific advice in the field from Dr. Ulrich Glawe from the School of Engineering and Technology and from Bretwood Higman, a senior doctoral student from the United States ' University of Washington in Seattle . They also consult by e-mail with Dr. Brian Atwater, a geologist with the U.S. Geological Survey. Funding comes in part from a U.S. government program that is providing technical support for Indian Ocean tsunami warning systems.
Higman, who has previously studied tsunami sands in Nicaragua, Sri Lanka, and Aceh, joined the AIT students this March at Bang Lut Beach in the Phang Nga Province in Thailand .
“AIT students have done a great job by digging, documenting and sampling 80, yes 80, such trenches,” Higman said. “During my visit we opened another eight trenches up to 10 meters in length and one meter in depth. We have very carefully sampled evidence in the tsunami deposits and I am proud to say that the Bang Lut area is probably the most intensively investigated location of a recent tsunami sand sheet in the world. It is a unique location and unique work of top quality has been done by my AIT student colleagues. Their results will be of tremendous interest and value for scientists in the tsunami community and many others.”
The students began their work in early 2005, and it will continue at least through the end of 2007.
Results of first attempts to link hydrodynamic phenomena of the tsunami to the sequence and type of sedimentation; sketched on a whiteboard in the field at Bang Lut Beach.
Alam, an advanced master's student in Geotechnical Engineering at SET said they are now looking at sand layers of different grain size and trying to see how the deposit matches with accounts of the waves.
“We find that when the flow is stronger, it carries coarser sediment and leaves a coarser layer on the ground,” Alam said. “As the flow speeds up or slows down, it leaves deposits that vertically vary in grain size. Putting all information together from different trenches, we are getting a clear picture about the incoming train of tsunami waves. Soon, we will finalize the laboratory analyses at AIT and in Seattle and find out and publish what has really happened on December 26, 2004 .”
If the researchers can match the changing grain size in the deposit to the surging of the tsunami waves, then they can also better understand prehistoric tsunamis from their deposits.
Students and other scientists want to understand buried evidence of ancient tsunamis that occurred before any recorded history, hundreds, or thousands of years ago. This is why they dig into the soil near the coast and look for layers of sand from tsunamis that they would otherwise never know about.
The young Asian scientists hope to be able to answer questions about ancient tsunamis using these deposits. How big were the tsunamis, and how fast did the water flow? Where did the tsunamis come from? And by dating the ancient tsunami sheets to answer questions such as, when did the last tsunami occur? and how often did they occur in the past? Questions like those are important for all stakeholders in areas with tsunami hazards such as along Thailand 's Andaman coast.