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Just curious: Tsunami possible within the Visayas?


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I am curious if there is any history of tsunamis within the Visaya archipelago or any other close island group?  It seems that there is not enough distance between the islands to allow large waves to form, unless the enclosed areas act like water in a bathtub, sloshing back and forth until the energy is dissipated.  The Bohol earthquake in 2013 did not seem to generate a tsunami warning.

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I'm moving next door to San Miguel factory! That way if the wave hits them first...I'll drown in a tsunami of beer !!!

Phivolcs has a good map called "Tsunami Prone Areas in the Philippines". (I'd upload it but the PDF is 35 MB).  But you can find it with Google. Heck, you can find anything with Google!        

The tsunami problem in the Tanon straight is because of the danger of underwater rockslide. There are large drop-offs like cliffs that could fall and produce tsunami like waves. I was in Tuble when th

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thinking of a beach front lot?  Water is the least of the problems

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The Bohol earthquake was under land. Tsunamis are caused by under sea earthquakes. There are six underwater fault lines between Bohol and Cebu, but it is impossible to know whether any of them are capable of generating a tsunami creating earthquake. Probably the biggest threat of tsunamis in the area is the Philippine Trench, which is the second deepest point in the world and just off the east coast of the archipelago, but it isn't likely that a tsunami generated by the faults in the Philippine Trench would have much effect on the central Visayan islands. The waves would have to pass through the Surigao Straits, which would weaken them. The east coast of the eastern Visayan islands are very vulnerable to any tsunami generated by the Philippine Trench. However, a strong typhoon could generate a storm surge that could rival a tsunami if it occurred at high tide regardless of where you are in the Philippines. Of course, there is a lot more warning with a typhoon than there is with a tsunami.

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BossHog

Phivolcs has a good map called "Tsunami Prone Areas in the Philippines". (I'd upload it but the PDF is 35 MB). 

But you can find it with Google. Heck, you can find anything with Google!

 

 

 

 

 

edit....www.phivolcs.dost.gov.ph/.../Tsunami_Prone_Map_Mar2013.pdf

Edited by BossHog
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6/2-2012 a quake of 6.7 had epicenter just 10 km from Panagsama in Tanon strait, closer to Negros. Cannot stand up, have to knee down.

 

And there was a tsunami but only 10 cm high. Half of water in my pool splashed out. All the people running Panagsama road to town (which is actually lower ground) were in panic of tsunami because they had media pictures from Japan tsunami of 2011 in their head.

 

Tanon strait not so wide so tsunami cannot evolve. I hope. We live by the sea but some 5 m up from sea level. No plans to move out  :cool:

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BossHog
I used this site when researching Argao, hopefully an area well protected from most geographical assaults, but everywhere has some risk I guess   http://vm.observator...ophys_maps.html

 

 

Interesting.

 

 

That site's map has the entirety of Cebu province marked as high risk to tsunami and most of the eastern coast of Samar rated as low risk:

 

post-5791-0-65028700-1481450302.jpg

 

Not what I would've expected, to be honest. Seems questionable. Also the map doesn't match their own top ten list.

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colemanlee

I would have thought Samar would be higher on the map....its closest to the trench..

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RogerDat

Is there an agency source for that map? With all the mis information circulating here lots of things on line are pure junk generated by people wanting to cause disturbances here.

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BossHog

I would have thought Samar would be higher on the map....its closest to the trench..

 

 

agreed

 

 

Is there an agency source for that map? With all the mis information circulating here lots of things on line are pure junk generated by people wanting to cause disturbances here.

 

 

True. It's a faulty (pun intended) map. That's why I questioned it.

 

The official Phivolcs map I linked to earlier is much more accurate.

 

After some effort I managed to take a screenshot:

 

post-5791-0-00317100-1481452647_thumb.jpg

 

post-5791-0-78866500-1481453066_thumb.jpg

 

ecit: legend enlarged and added for legibility.

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The damage from a tsunami is not going to be the same for each island. The tsunami will be affected by the outlying seabed. Each seabed has different characteristics which effects the runup of the tsunami wave.

 

The origins of tsunamis is not just local (nearby) seismic activity. They can originate thousands of km away.

 

I spent time in Seattle and even in that area tsunamis were considered to be a real threat.

 

Of course there's always the Space Needle!

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Dafey

I'm moving next door to San Miguel factory! That way if the wave hits them first...I'll drown in a tsunami of beer !!!

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BossHog
The origins of tsunamis is not just local (nearby) seismic activity. They can originate thousands of km away.

 

We've had two evacuations in the past here on Siargao in my memory for potential tsunamis caused by major Chilean quakes.

 

To the best of my memory the lead time was about twelve hours.

 

Of course if the trench offshore goes the lead time will be a heckuva lot shorter.

 

There is a Philippine government siren and clearly marked tsunami evacuation routes in the village though. Hey, it's something!

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We've had two evacuations in the past here on Siargao in my memory for potential tsunamis caused by major Chilean quakes.

 

To the best of my memory the lead time was about twelve hours.

 

That's probably about right. From memory, tsunami waves travel at close to the speed of sound, so it would be about the same as a trans-Pacific flight.

 

As far as the Cebu Metro area goes, I'm not too worried about tsunamis (of course I don't live too close to the coast). It takes a pretty big earthquake (like in excess of 8.0) to create a tsunami of any size (and even then, it must be a vertical slip fault rather than a horizontal slip fault). If an earthquake that size hit in the Bohol Straits, the tsunami would be the least of our worries. There would be landslides everywhere, and most buildings and infrastructure would be destroyed.

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