MASS-Andaman-Sea (Morphodynamics and Slope Stability of the Andaman Sea Shelf Break) is a research project in the framework of the Thai-German cooperation TRIAS (Tracing Tsunami impacts on- and offshore in the Andaman Sea Region). 

The MASS project aims in assessing the potential risk for tsunamis generated by submarine slumping of the Andaman Sea shelf break off the west coast of Thailand. Since December 26, 2004 when a devastating tsunami generated by an earthquake off Sumatra hit the west coast of Thailand, claimed the lives of many people and destroyed large areas along the coast, the potential risk for future tsunami events in that area is of major concern to the Thai people and the scientific community. Aside the risk for tsunamis generated by large earthquakes along the Sunda Arc subduction zone, submarine slumping could be a potential cause for tsunamis in the Andaman Sea. Little is known about the sea-floor and the tectonic structure of the Thai part of the Andaman Sea.

In the first phase of the project (2006 - 2008), bathymetric data were collected in order to characterize the seafloor. Numerous interesting features were identified including escarpments, individual mud volcanoes, indications for fluid seepage and a possible relationship between fluid seepage and slope stability. The initial phase of the project, however, demonstrated that additional data are needed to assess slope stability and possible consequences of a major slide. Bathymetric data set needs to be extended but the main focus will be on the collection of seismic data and seafloor sampling. Seismic data are needed to image older mass flow deposits and therefore the recurrence rate of major mass wasting events, which is essential for a risk assessment. Seismic data will also help to identify gas hydrates in order to analyze their role for slope stability in the Andaman Sea. Cores are needed for sedimentological and geotechnical analysis as well as for dating of individual slide events. The data will be collected during a cruise on the Thai Research Vessel Chakratong Tongyai.

 

Research objectives

• Acquisition and processing of new acoustic and core data: 
  Acoustic data will be used to identify and map headwalls, escarpments, debris deposits and other evidence of slope failures and down-slope mass transport. Based on the acoustic data cores will be taken for sedimentological and geotechnical analyses.
• Quantification of individual mass wasting events. 
  Seismic and bathymetric data can be used to quantify individual mass wasting events. The volume of mass wasting events is an important factor for its tsunami potential.
• Characterisation of slope failures. 
  All slope failures will be classified in order to distinguish between creeping, sliding and slumping as well as between single and multiple failure events. This classification will help to differentiate between sequential and catastrophic events.
• Determination of sedimentary properties. 
  Cores will be taken in order to determine sedimentary properties from normal (background) sedimentation, from creeping sediments and from areas affected by catastrophic slope failures. Such investigations help to assess the stability of the slope.
• Age determination of mass wasting events. 
  Sediments immediately above and below the failed sediments will be dated to establish ages of slope failures.
• Frequency of slope failures. 
  Seismic data allow to image older buried mass wasting event. The seismic data set should be used to determine the recurrence rate of slope failures. The data will also show if some parts of the slope experienced repeated slope failures.
• Analysis of near surface gas hydrates and fluid seepage. 
  Numerous seepage features were found in the available data set. Gas hydrate occurrence is not proven but very likely. A first analysis of the data might indicate a relationship between slope stability, gas hydrate occurrence and fluid seepage, which should be studied in detail in an area, where the gas hydrate stability zone reaches the sea floor.
• Correlation of very recent (small scale) failure events with regional seismicity. 
  Earthquakes are the most likely trigger for slope failure in the Andaman Sea. We want to test whether individual mass wasting events can be correlated with seismicity and local faults.
• Determination of the current state of the slope. 
  A synthesis of all available data will allow to characterize the current state of the slope and to should lead to a risk assessment for future slope failures.