3 ms·
That shakemap looks really suspicious, relative to the damage being reported in Thailand, especially Bangkok. 600 miles away (~1000 km) and the shakemap's repo
by araes 2y ago
That shakemap looks really suspicious, relative to the damage being reported in Thailand, especially Bangkok. 600 miles away (~1000 km) and the shakemap's reporting numbers like 3 to 4 on the intensity scale. When they reported the skyscraper collapsing in Thailand, at first I thought it was Chiang Mai near the border of Myanmar, not Bangkok 600 miles away. For Americans, that's like the big one hits the Cali fault, and skyscrapers are falling down in Salt Lake City or Phoenix.
Wonder whether that's just automated simulation output, rather than actual measurements from stations? Numbers 3 and 4:
3 - Felt noticeably indoors, especially in tops of buildings, yet many do not even notice there's an earthquake.
4 - Felt indoors by many, felt outside by few. Sensation like heavy truck striking a building.
Bangkok's reporting sensations, crowd behavior, and events more like a 6 to 7. Everybody runs, furniture moves, plaster falls, considerable damage to poorly built (partially finished) structures. A 3-4 is like, you barely notice, or think a really heavy vehicle just crashed or something. Not, everybody in town runs in panic, describes all the ceilings collapsing, cracks in walls afterward. [1][2][3][4]
Expect there's probably going to be some re-evaluation of the magnitude and scale of the earthquake based on what was actually reported by observers, cameras, and damage afterward. They're reporting slight damage and cracks even in relatively well constructed buildings.
Edit: This story from ChannelNewsAsia in Singapore has camera footage from somebody on the ground near the skyscraper collapse. Visibly shaking the camera holder. [5]
[1] Intensity, Text Descriptions: https://sciencefest.indiana.edu/wp-content/uploads/2020/10/mmi_table-Elizabeth-Sherrill.jpg https://sciencefest.indiana.edu/wp-content/uploads/2020/10/m...
[2] Semi-common Cone Chart with Energy Comparison: https://basecampconnect.com/wp-content/uploads/2022/01/eartquake20frequency20and20destructive20power.jpg https://basecampconnect.com/wp-content/uploads/2022/01/eartq...
[3] Japanese Chart with Pictures: https://miro.medium.com/v2/resize:fit:1400/1*Ca_yV0l_zkWiFtgRttb4sA.jpeg https://miro.medium.com/v2/resize:fit:1400/1*Ca_yV0l_zkWiFtg...
[4] Another Picture Chart: https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/production/s3fs-public/thumbnails/image/Earthquake%20Intensity%20Scale%20%28Transparent%20PNG%20for%20Print%20and%20Web%29.png https://d9-wret.s3.us-west-2.amazonaws.com/assets/palladium/...
[5] ChannelNewsAsia, https://www.channelnewsasia.com/asia/massive-quake-kills-nearly-150-myanmar-thailand-5030921 https://www.channelnewsasia.com/asia/massive-quake-kills-nea...
- baq 2y agoThe geometry of the fault may have something to do with it, maybe some constructive interference at play...?
- dnawy 2y agoUSGS Shakemap intensity is based on the peak ground acceleration (PGA). It has been known that, in some cases, PGA does not correlates well with structural damages. The peak ground velocity (PGV) has better correlation with structural damages [1]. Even so, they are only describing the peak values, it does not describe the ground motion frequency or other ground motion characteristic [4]. It is hard to compress a complex phenomenon into single value. My colleagues suspect that the soil condition in Bangkok (soft soil and basin) and the distance from the epicenter amplifies long period/low frequency content of earthquake waves, making skycraper to be more vulnerable to damages. Example of basin effect is 1985 Mexico City Earthquake [2] and example of long period effect is the 2011 Tohoku EQ [3] (Note: Magnitude value would probably be stable, they are based on the energy released by the earth (Moment Magnitude), Intensity is just the on-the-ground observation of the earthquake and it can be subjective.) [1] https://www.cwa.gov.tw/Data/service/hottopic/20191213_SC_NewInt.pdf https://www.cwa.gov.tw/Data/service/hottopic/20191213_SC_New... ; https://www.ncdr.nat.gov.tw/CEOCworkshop/cwb_2.pdf https://www.ncdr.nat.gov.tw/CEOCworkshop/cwb_2.pdf [2] https://en.wikipedia.org/wiki/1985_Mexico_City_earthquake https://en.wikipedia.org/wiki/1985_Mexico_City_earthquake [3] https://en.wikipedia.org/wiki/Long_period_ground_motion https://en.wikipedia.org/wiki/Long_period_ground_motion [4] https://www.iitk.ac.in/nicee/wcee/article/WCEE2012_5499.pdf https://www.iitk.ac.in/nicee/wcee/article/WCEE2012_5499.pdf
- mikhailfranco 2y agoBangkok is built on a muddy floodplain. The soft ground accentuates the ground motion by the jello-wobble resonance effect. High-rise buildings that do not have seismic isolation or counter-weight damping (like Taipei 101) will suffer dramatic whiplash shaking at the top. https://www.atlasobscura.com/places/tuned-mass-damper-of-taipei-101 https://www.atlasobscura.com/places/tuned-mass-damper-of-tai... Some cities closer to the epicenter, such as Chiang Mai, are also on floodplains, but have many fewer high-rise buildings. Some smaller condo blocks there have been deemed unsafe after the earthquake. https://www.chiangmaicitylife.com/citynews/general/following-earthquake-four-buildings-deemed-unsafe-until-further-inspection/ https://www.chiangmaicitylife.com/citynews/general/following...