7.5 Earthquake hit Taiwan

[NotHardUp1]

https://www.reuters.com/world/asia-pacific/strong-72-magnitude-earthquake-hits-taipei-2024-04-03/

There appears to be no tsunami, and death toll low, so far. It is the strongest to hit the island in the last 25 years.

Estimates have ranged between 7.2 and 7.5 on the Richter Scale.

 

[rareboy]

Ouch

 

[Latimer]

It seems from these pictures that the damaged buildings collapsed due to a soft story:

A number of similarly under-engineered buildings collapsed in Los Angeles during the Northridge earthquake in January of 1994. The city is filled with 2-story "dingbat" (I believe they were so named by the English architect Reyner Banham) apartment buildings built cheaply in the 50's and 60's where much of the ground is given over to carports and the upper floor is supported by spindly pipe columns.

The Northridge quake was 6.5 and absolutely terrifying. I remember that, when the shaking stopped, I thought, with relief and elation, "Finally, the Big One, and we survived!" only to later discover that, at 6.5, we hadn't come close. The Big One is predicted to be 8.0.

How Earthquakes Work

The Richter Scale is used to rate the amount of energy an earthquake releases. Learn how the Richter Scale is calculated and what the ratings mean.

science.howstuffworks.com

The first thing I do when I enter a large, covered space in California is check for the exits. A few years ago, I remember taking my seat in the half-open concert space at Tanglewood in western Massachussetts, thinking, "This is the first time in years I haven't been to a concert and though of a potential earthquake.

A few years ago, when my partner and I were booking a room in a high-rise hotel in Tokyo, I went online to check out the seismic engineering reports of the office buildings where the hotels were located and review the portfolios of the structural engineers. I surmised from the abundant material available that sophisticated structural engineering and earthquake safety precautions were considered of great value in marketing the building.

 

[NotHardUp1]

The first thing I do when I enter a large, covered space in California is check for the exits. A few years ago, I remember taking my seat in the half-open concert space at Tanglewood in western Massachussetts, thinking, "This is the first time in years I haven't been to a concert and though of a potential earthquake.

A few years ago, when my partner and I were booking a room in a high-rise hotel in Tokyo, I went online to check out the seismic engineering reports of the office buildings where the hotels were located and review the portfolios of the structural engineers. I surmised from the abundant material available that sophisticated structural engineering and earthquake safety precautions were considered of great value in marketing the building.

Before I moved to Anchorage in 2007, I read up on the Good Friday quake in 1964, remembering the severity of it.

Over 600 miles of land along the fault moved.

Some places shifted by as much as 65 feet.

The quake lasted almost five minutes. That's long enough to convert to three separate religions and back to atheism.

Analysis suggested the tension released had been building for 500 years.

At 9.2 on the Richter, it was the strongest recorded quake in North America.

So, after studying it, I decided I wasn't going to be afraid. It was a one-off in the life span of a human. While I lived there, a volcano went off along the archipelago, and we had a 5.0 quake, but it barely shook my house.

It's an awe-inspiring level of force we try to counter as we design and build bridges and towering buildings. That said, I seriously doubt any of our major cities could withstand a 9.0, much less for five minutes. There is only so much brick and stone and steel can do.

 

[Latimer]

California now has an early warning system. About a minute before the last earthquake of note in our area I received an alert on my phone, just as I have over the last week received warnings regarding potential flash flooding.

 

[Vannie]

Just had a 4.8 hit NJ area

That pretty good for NJ

All my Fire King Jadeite was shaking.

 

[Kulindahr]

The Big One is predicted to be 8.0

The Big One here in the Pacific Northwest is calculated to be a potential 9.2.

I've been in a 6.0 and a 5.4; the 5.4 was unsettling, the 6.0 was scary. I've also experienced a 2.4, a 2.7, and a 4.1; the first two were barely noticeable, the 4.1 was missed by a lot of people -- many said it just felt like heavy equipment driving by.

 

[Kulindahr]

At 9.2 on the Richter, it was the strongest recorded quake in North America.

They redid the scale, making it a 9.0 -- at the peak; there were actually several quakes over several minutes, between 8.7 and 9.0. It's a great example of a cascade effect on a slip-fault line: one stuck point gives way, putting stress on others; they give way, putting stress on still more. One paper I read concluded from the records that Alaska had seven quakes in those five minutes.

BTW, in such a cascade effect on a slip fault the original point can get stuck and give way again -- not likely, but possible.

And the estimated power of our Pacific Northwest Big One is 9.2 on the new scale -- and there's something like 0.5% chance in any of the next fifty years that it will happen! I talked with a geologist who specialized in quakes who said that the smallest tsunami on my stretch of coast would be eight feet high, the worst case sixty feet . . . yet the county's maps of tsunami-vulnerable areas barely reach town! I think they're counting too much on the bay absorbing most of it, though at even halfway to maximum the tsunami will just wash over the sandspit and into the bay without really slowing down. Our best hope is if it happens on an exceptionally low tide; that would just bring the bay level up to an ordinary high tide.

 

[EddMarkStarr]

The year 2024 may have more surprises to spring on the world!

 

[Kulindahr]

That said, I seriously doubt any of our major cities could withstand a 9.0, much less for five minutes. There is only so much brick and stone and steel can do.

I read a report about our coming Big One here recently where engineers estimated that only 15% of structures within sixty miles of the coast are earthquake-ready. For those who live in wooden houses they recommended diagonal steel bracing on all walls and extra-heavy duty steel brackets bolting to the foundation (apparently most wooden houses do fine in earthquakes if they manage to stay on the foundation).

 

[Kulindahr]

California now has an early warning system. About a minute before the last earthquake of note in our area I received an alert on my phone, just as I have over the last week received warnings regarding potential flash flooding.

We've got a local warning system -- actually two of them, one for the quake and tsunami, one for the dam up in the hills which is rated for a 7.5, not for anything bigger.

 

[NotHardUp1]

They redid the scale, making it a 9.0 -- at the peak; there were actually several quakes over several minutes, between 8.7 and 9.0. It's a great example of a cascade effect on a slip-fault line: one stuck point gives way, putting stress on others; they give way, putting stress on still more. One paper I read concluded from the records that Alaska had seven quakes in those five minutes.

But the quake had to abide by the law in effect at the time.

Methinks they get to count aftershocks as the Main Event when they all happen continuously.

Anything in a 9.0 range is apocalyptic. And to think they went on for that long is nothing less than horrific. Were that to strike a real metropolitan area, the death toll would be in the many thousands, no matter what the building codes.

I'm thankful I cannot imagine the terror those people felt as it continued for five minutes. Just chills to the bone.

It was a great example of the gods were angry.

 

[Kulindahr]

Methinks they get to count aftershocks as the Main Event when they all happen continuously.

I think it was a matter of having several different hypocenters that were significantly separate.

Anything in a 9.0 range is apocalyptic.

Up until recently geologists predicted that the Pacific NW Big One would be "only" an 8.2. The announcement that the prediction has changed to 9.2 has a lot of people scared. That's powerful enough it could essentially liquefy the ground under pretty much the entire valley -- towns, farms, and all. Several towns here are built on sand that can also liquefy.

And to think they went on for that long is nothing less than horrific.

The 6.0 I experienced lasted all of 45 seconds or so; the 5.4 went on for almost a minute. I don't even want to think about how bad something five times that long would be!

I'm thankful I cannot imagine the terror those people felt as it continued for five minutes. Just chills to the bone.

No kidding. And understanding the mechanism of what's going on really makes it worse!

Not long ago I was telling some folks about the conservation work I was doing. One thing I pointed out was the sandspit that borders and makes the bay -- it has high, forested dunes in the middle, and they get lower towards each end. That's the result of past Big Ones: there's an igneous cape to the north and another to the south, and regardless of which way a tsunami comes from debris from the quake will end up in the middle of that stretch of coastline. One person said "That must be a really big wave!" and I told them how geologists think the last big tsunami that hot here was forty feet high. This was immediately followed by "What do we do if a quake hits?"
No one was happy with my answer because basically everything and everyone on the spit is toast; the only hope is that there's a foreshock that will warn people, and even then most people won't be able to get away.