Although you cannot totally discard the existence of an active fault, it seems to be no clear evidence of that. In the first profile, the "vertical discontinuity" could be just an artifact because you cannot distinguish any displacement on both sides. The area to the right side of this discontinuity seems to be quite suspicious due to the lack of good resolution but, if you look above and under this area, there is no clear evidences of displacement. Particularly, if you look for "active faulting" (I assume you mean that the younger units were deformed), you should find the structures affecting the uppermost levels, which is clearly not present. The second case could be a bit more debatable. Perhaps you could interpret a subvertical structural (slightly dipping to the right) but it is again not possible to see any clear displacement. Actually, if you consider this as a fault, then you can intepret many order similar features in your profile. I would think that it is more an artifact than a real structure. Hope this comment can help you and you can succeed in solving this problem.

I think on the top profile there is pretty clearly a subvertical fault (I don't know the vertical exaggeration). The stratigraphic separation is down to the right, maybe 7 or 8 of your units (milliseconds?). But, it is unclear where the sea floor is above the prograding unit. Is the strong reflecton sea floor and the weaker reflections some sort of artifact? Or, is there a younger unit there about 5 units thick? If the latter, then there is no vertical separation of that unit. Whether the fault would be called "active" depends on the ages of the units and the legal definition of "active" in that country.

For the second profile, it is less clear whether there is a fault. You are not providing nearly enough information. Where is this? What are the scales?  What is the acquisition and processing? Also, better to show the top of the profile, 0 seconds, so that it is easier to interpret the multiples.

Chris

Thank you, The unit is millisecond. Here are more detail images. there is coral reef in this area.

Dear Phan,

It is very difficult to say from a seismic profile alone if a fault is active or not.  If your are is not tectonically very active, you can only determine this in two ways in my opinion.  You will have to investigate the earthquake seismology for your area of investigation to see if there are any recent locations of events that coincide with your fault location, OR you would have to open it up and investigate to see if you could find any neo-tectonic evidence.  You could also drill the fault, study the core for that and try to date the material, that will place an approximate age of the faulting.

However, the seismicity, and even the micro seismicity is the best and cheapest.  If you can, deploy a few mobile stations in the area for 3-6 months or so, and hope for the best that there will be some movement that will indicate micro-seismicity.  Then you will know for sure.

Hope this helps.

Regards

Stoffel