7.4 earthquake in Taiwan, 34km depth • Hacker News Board

Re: 7.4 earthquake in Taiwan, 34km depth

#171

Post by PaulHoule » Wed, Apr 03, 2024, 4:24 PM UTC

shiroiushi wrote: post #111

PaulHoule wrote: post #52

Earlier quoted context omitted.

Consider for instance this place https://commons.wikimedia.org/wiki/Category:Diablo_Canyon_Po... which is on top of a high bluff thus much more secure than the Fukushima NPP.

Unfortunately, that power plant is very close to two fault lines, and they didn't even know when they built it, so it's questionable how well it'll withstand an earthquake. https://en.wikipedia.org/wiki/Diablo_Canyon_Power_Plant

They increased the anticipated seismic loads and also reinforced the structure accordingly. I don’t think any NPP has been scrutinized to the extent that Diablo has been.

Re: 7.4 earthquake in Taiwan, 34km depth

#172

Post by appleiigs » Wed, Apr 03, 2024, 4:33 PM UTC

wiredfool wrote: post #149

hojinkoh wrote: post #117

Earlier quoted context omitted.

I can't imagine how terrifying it will be if I was on Taipei 101 during this quake...

You shouldn't be. Tall buildings (> 40 floors) are one of the safer places to be in an earthquake. 1) They're engineered. 2) They're already designed for side loads from wind. 3) Their fundamental frequency is well lower than the peak of the earthquake spectrum, so they don't amplify the motion. Good rule of thumb is that period = floors/10, so fo a 50 story building you're looking at a 5 second period. Earthquakes h…

> 1) They're engineered.

Famous last words.

Re: 7.4 earthquake in Taiwan, 34km depth

#173

Post by hnfong » Wed, Apr 03, 2024, 4:34 PM UTC

doodlebugging wrote: post #151

spxneo wrote: post #99

this guy is right again at predicting these earth quakes: https://twitter.com/ssgeos/status/1775146068079960148

Alright. I'm a bit of a geophysicist (oil industry though, not seismology) so I figured I would take a look at this to see whether it holds up to any serious scrutiny. I'm also a huge sceptic and a cynic, only moderately prone to sarcasm but I'm gonna do my best here. It took a bit of work to dig thru the claims he makes. His claims involve planetary alignments serving as a trigger for earthquake activity so that a c…

> I wonder why I have wasted so much of my life assembling this tonight. I should've been sleeping.

I know that feel :)

If it makes you feel better, I read through the whole thing and gave you an upvote. Peace :)

Re: 7.4 earthquake in Taiwan, 34km depth

#174

Post by Someone » Wed, Apr 03, 2024, 6:07 PM UTC

yosito wrote: post #50

s_m_t wrote: post #24

Earlier quoted context omitted.

It can be a very long wave. If you have a coastal area that is mostly at or very close to sea level then that entire area could now be 3m underwater which is very bad. Also, even under normal conditions the type of wave you would see at the beach with a height of 3m is insanely powerful. I think the highest I have body surfed in was maybe 2-2.5m and if you get caught in the break of the wave you are literally powerle…

Yep, where I live (rent) a 3m wave would fill my house with 1m of water. Even if it was one quick wave, that washed over without staying long enough to completely flood the inside of my house, I'd probably at least have to deal with a bunch of water damage.

I would be more worried about the force of the water hitting things and about objects it drags with it than about water damage.

One meter of water weighs 1000kg/m². If a wave a few meters long slams into a wall of your house, that can easily be more force than that of a decent sized car doing the same.

Re: 7.4 earthquake in Taiwan, 34km depth

#175

Post by doodlebugging » Wed, Apr 03, 2024, 6:08 PM UTC

hnfong wrote: post #173

doodlebugging wrote: post #151

Earlier quoted context omitted.

Alright. I'm a bit of a geophysicist (oil industry though, not seismology) so I figured I would take a look at this to see whether it holds up to any serious scrutiny. I'm also a huge sceptic and a cynic, only moderately prone to sarcasm but I'm gonna do my best here. It took a bit of work to dig thru the claims he makes. His claims involve planetary alignments serving as a trigger for earthquake activity so that a c…

> I wonder why I have wasted so much of my life assembling this tonight. I should've been sleeping. I know that feel :) If it makes you feel better, I read through the whole thing and gave you an upvote. Peace :)

Peace to you too pardner. I appreciate you sticking with me all the way through.

Re: 7.4 earthquake in Taiwan, 34km depth

#176

Post by saltcured » Wed, Apr 03, 2024, 6:43 PM UTC

lukan wrote: post #153

dylan604 wrote: post #35

Earlier quoted context omitted.

i'm always amazed how little appreciation people have for massive amount of water. a 3m wave will more than ruin your day. trust me, it's plenty

Well, I was in the ocean saving a person getting caught by such a big wave on the beach, so I do appreciate the power of the water here. But I think 3 m waves are quite normal on most coast lines in rough sea. So my question was, why would a Tsunami of the same height be that much worse. And in comparison to the destruction of the earthquake in general here.

A 3 m tsunami isn't like a 3 m wave from wind action. It is like a 3 m tide or storm surge added on top of whatever normal tide level you are at. So if it hits at low tide it might be somewhat negated, but if it hits at high tide it may overwhelm sea walls and other coastal infrastructure.

When people talked above about the long wavelength of a tsunami, they mean it doesn't crest and possibly break in seconds like a surface wave. It can keep building for many minutes and continue to flow inland after the crest.

Look for some tourist video of the 2004 tsunami that flowed over islands in Thailand. It looks more like a river or levee breach flooding over the whole field of view. In steeper coastal terrain, the wave can sometimes be funneled or focused into a narrower port or valley and then reach much higher elevations than you would expect.

Re: 7.4 earthquake in Taiwan, 34km depth

#177

Post by isthatafact » Wed, Apr 03, 2024, 6:59 PM UTC

spxneo wrote: post #108

dylan604 wrote: post #106

Earlier quoted context omitted.

this is the first time i've ever seen this person. how is he received in non youtube audiences? is this fringe level stuff, or is this accepted science? i have a hard time wrapping my head around a planetary alignment with Neptune affecting Earth. I'm not dismissing it, but my knee jerk is this can't be real, yeah?

his track record indicates this is not a random reinforcement but something worth looking into. I also didn't know what this planetary alignment is but there have been papers around it.

Without independent statistical analysis, he has no "track record".

Re: 7.4 earthquake in Taiwan, 34km depth

#178

Post by smcin » Wed, Apr 03, 2024, 7:09 PM UTC

smcin wrote: post #64

Pufferbo wrote: post #44

What’s the significance of an earthquake’s depth?

Shallower earthquakes cause much more damage (on the surface), esp. if near densely populated areas; also depends greatly on how earthquake-proof structures and buildings are. Today's one was 34km deep/21 miles. 1989 SF (Loma Prieta) was magnitude 6.9, epicenter 56 mi south of SF, depth 11 miles. (Typical California earthquake focal depths are 4 to 6 miles). 1906 huge SF earthquake was magnitude 7.9, depth 5 miles. 2…

This CNN article hs a list of previous Taiwan earthquakes, magnitude, location, deaths and injuries, but not depth: https://www.cnn.com/2024/04/02/asia/taiwan-earthquake-tsunam...

Re: 7.4 earthquake in Taiwan, 34km depth

#179

Post by wiredfool » Wed, Apr 03, 2024, 8:42 PM UTC

appleiigs wrote: post #172

wiredfool wrote: post #149

Earlier quoted context omitted.

You shouldn't be. Tall buildings (> 40 floors) are one of the safer places to be in an earthquake. 1) They're engineered. 2) They're already designed for side loads from wind. 3) Their fundamental frequency is well lower than the peak of the earthquake spectrum, so they don't amplify the motion. Good rule of thumb is that period = floors/10, so fo a 50 story building you're looking at a 5 second period. Earthquakes h…

> 1) They're engineered. Famous last words.

They're more engineered than a 6 story apartment building.

(civil engineer by training, though never got a PE because startups)

Re: 7.4 earthquake in Taiwan, 34km depth

#180

Post by EdwardDiego » Wed, Apr 03, 2024, 9:10 PM UTC

robocat wrote: post #21

xattt wrote: post #7

I see earthquake reports (like this one) describe earthquake depth. What is the significance of it? Is it somehow actionable?

A shallow 6 is very different from a deeper 7. My city Christchurch was fucked by a 6.2 or 6.3 - but it was both (a) shallow (5km) and (b) close to dense residential areas. Christchurch was near to the 7.1 Canterbury earthquake but that did much less damage as it was 10km deep and Christchurch wasn't on top of it (it mostly affected less dense rural properties in the region near Christchurch). Be careful not to think…

IIRC another aspect was that the fault-line that did Feb 22 was underneath the Port Hills, and the volcanic rock deflected the energy towards the city.