Tsunami in Zihua Bay?

by HolyMole @, Sunday, September 30, 2018, 12:48 (73 days ago)

The recent Indonesian tsunami raises a question: what effect might a tsunami have on Zihua Bay, (and Zihua Centro), given the shape of the Bay, with a relatively small mouth facing open ocean? Would the Bay's shape amplify or reduce the potential impact?
I recall a tsunami scare in Zihua a few winters ago. Some people said they were going to seek higher ground, just in case. Others set-up their beach chairs at the water's edge in front of Paty's on La Ropa, margaritas in hand.

Tsunami in Zihua Bay?

by The Fez ⌂ @, Sunday, September 30, 2018, 18:50 (73 days ago) @ HolyMole

Tsunamis pose their greatest danger for Zihua Bay if in a direct line from the epicentre based on the orientation of the bay. By looking at a map of the Pacific you can see that the recent earthquake/tsunami which originated near the island of Sulewesi in Indonesia couldn't make a beeline to Zihua since Papua New Guinea, Mindanao, and Malaku islands are in the general path. Also, if you hear news of an earthquake caused tsunami from the other side of the ocean, you would have some time to prepare, since they generally move at about 800 km/h and Indonesia is over 15,000 km away, giving you about 18 hours lead time.

Tsunami in Zihua Bay?

by HolyMole @, Sunday, September 30, 2018, 19:29 (73 days ago) @ The Fez

Tsunamis pose their greatest danger for Zihua Bay if in a direct line from the epicentre based on the orientation of the bay. By looking at a map of the Pacific you can see that the recent earthquake/tsunami which originated near the island of Sulewesi in Indonesia couldn't make a beeline to Zihua since Papua New Guinea, Mindanao, and Malaku islands are in the general path. Also, if you hear news of an earthquake caused tsunami from the other side of the ocean, you would have some time to prepare, since they generally move at about 800 km/h and Indonesia is over 15,000 km away, giving you about 18 hours lead time.

My question was rhetorical. I realize there's little chance of a tsunami generated in the islands of Indonesia having much effect in Zihua.....nor was I wondering about lead time. Will the shape of Zihua Bay and the orientation of the mouth of the bay amplify or reduce the potential for damage? I believe you are correct that most damage would result from waves generated in a direct line, which is probably unlikely. Just as the Bay's northwest(?) opening provides some protection from tropical storms, I assume the same would apply to a tsunami.

Tsunami in Zihua Bay?

by The Fez ⌂ @, Monday, October 01, 2018, 22:51 (72 days ago) @ HolyMole

In reality, an Indonesian earthquake/tsunami could actually be a big problem for the bay in Zihua. The 1960 Chilean quake caused extensive damage in far-flung Hawaii, a 10,000 km distance from the epicentre. And the shape of the bay could funnel a tsunami into a nasty event, as it was last week in Sulawesi, where most of the destruction occurred in a long bay. It's just a matter of what's in the line of sight. If there's nothing, it'll be bad.

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Tsunami in Zihua Bay?

by Curly! ⌂, Great Pacific Northwet, Monday, October 01, 2018, 11:01 (72 days ago) @ HolyMole

There was indeed a tsunami in the bay a number of years ago. If you take time to search the archives, you might even find some video links.

--
Curly!
Zihuatanejo Trip Reports

Tsunami in Zihua Bay?

by HolyMole @, Monday, October 01, 2018, 11:33 (72 days ago) @ Curly!

There was indeed a tsunami in the bay a number of years ago. If you take time to search the archives, you might even find some video links.

That's the one I was referring to, and although there may have been a short-lived surge of a foot or so, thankfully it was pretty much a non-event. I was one of those who thought of higher ground, but ended up staying at Paty's.

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Tsunami in Zihua Bay?

by Talley Ho @, Monday, October 01, 2018, 11:36 (72 days ago) @ HolyMole

The RVing in Mexico and South America Forum had an interesting discussion of tsunami's.
It starts in the middle of the second page:

https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29564628/srt/pa/pging/1/page/1.cfm

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Tsunami in Zihua Bay?

by Fran @, Evanston, IL, Tuesday, October 02, 2018, 09:47 (71 days ago) @ HolyMole

I recall that after the major earthquake in Mexico City in the 1980’s there was a significant tsunami event in Zihuatanejo Bay. I recall it was described by the man who was the original owner of Villa del Sol in a Time magazine article. It made an impression on me.

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Tsunami in Zihua Bay?

by ZihuaRob ⌂ @, Zihuatanejo, México, Tuesday, October 02, 2018, 10:41 (71 days ago) @ Fran

I recall that after the major earthquake in Mexico City in the 1980’s there was a significant tsunami event in Zihuatanejo Bay. I recall it was described by the man who was the original owner of Villa del Sol in a Time magazine article. It made an impression on me.

Tsunamis have devastated this region several times since humans have lived here. The ruins at La Chole are probably the best example of this. The fact that Zihuatanejo was never a principal population center until relatively recently speaks volumes. Look at any Google Map and take a good look at Playa Blanca and you should be able to make out the geological effects of several successive tsunami events. My wife has seen the bay empty out about a third of the way. When the water returned it flooded all the homes in Zihuatanejo. The only saving grace is that the shape of the bay acts a bit like a shock absorber and takes a lot of the impact out of massive inflow of rushing water. We see this commonly with the groundswells that cause severe damage along most of the nearby coastline along the open ocean while only causing minor erosion along the beaches in the bay.

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Tsunami in Zihua Bay?

by Fran @, Evanston, IL, Tuesday, October 02, 2018, 15:41 (71 days ago) @ ZihuaRob
edited by Fran, Tuesday, October 02, 2018, 20:07

The man in the Time article (Helmut?) talked about the Bay emptying and leaving the beach very quickly before it barreled back in. I have seen the regression on the beach in Lake Michigan during a seiche. It can’t compare to a tsunami but when the lake recedes and barrels in, it gets your attention and I have the sense about how devastating it could be.

Tsunami in Zihua Bay?

by HolyMole @, Tuesday, October 02, 2018, 16:40 (71 days ago) @ ZihuaRob

I recall that after the major earthquake in Mexico City in the 1980’s there was a significant tsunami event in Zihuatanejo Bay. I recall it was described by the man who was the original owner of Villa del Sol in a Time magazine article. It made an impression on me.


Tsunamis have devastated this region several times since humans have lived here. The ruins at La Chole are probably the best example of this. The fact that Zihuatanejo was never a principal population center until relatively recently speaks volumes. Look at any Google Map and take a good look at Playa Blanca and you should be able to make out the geological effects of several successive tsunami events. My wife has seen the bay empty out about a third of the way. When the water returned it flooded all the homes in Zihuatanejo. The only saving grace is that the shape of the bay acts a bit like a shock absorber and takes a lot of the impact out of massive inflow of rushing water. We see this commonly with the groundswells that cause severe damage along most of the nearby coastline along the open ocean while only causing minor erosion along the beaches in the bay.

Thanks. That's the kind of info I was seeking.