5 ms·

One thing I noticed is that when the US talks about earthquakes, it often only notes the seismic magnitude value of the quake and doesn't always mention the sei

One thing I noticed is that when the US talks about earthquakes, it often only notes the seismic magnitude value of the quake and doesn't always mention the seismic intensity scale values of the affected locations. This is in contrast to Japan where quakes are almost always mentioned in both magnitude and the Japan Meteorological Agency's "shindo" intensity scale [1], eg. "The 2011 Tohoku Earthquake was a M9.0 quake with a maximum intensity of shindo 7." The US does have the equivalent of the JMA shindo scale - the Modified Mercalli (MM) scale [2], and they do seem to be used, but I see the MM values mentioned much less frequently than how both the Japanese agencies and the general public refers to shindo values. While the magnitude value signifies the overall energy of the quake, intensity scale values indicate the shaking intensity of a given location; hence, it feels more grounded in one's daily life experiences. Many Japanese individuals have developed an approximate sense of how strong a quake is - conversations like "That was a bit big, somewhere around shindo 4?" are common after quakes. People do of course care about magnitude, but the thing they care most about after a big quake is more likely "what was the seismic intensity in the worst-hit area?" Any idea why intensity scales seem to be much less common in the US? [1] https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_seismic_intensity_scale https://en.wikipedia.org/wiki/Japan_Meteorological_Agency_se... [2] https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_scale https://en.wikipedia.org/wiki/Modified_Mercalli_intensity_sc...

bribroder 7y ago
It might be a data collection problem--the JMA has deployed a pretty dense network of sensors over their entire territory, which makes sense given how geologically active it is. In fact the Earthquake Early Warning's "next steps" plan says "New sensors need to be added in California to shorten the CISN sensors spacing to approximately 12 miles to facilitate timely EEW. The shorter the station spacing, the smaller the blind zone will be because warnings can be issued faster." Check out this map comparison of the two networks: https://earthquake.usgs.gov/research/earlywarning/images/stationdensity.JPG https://earthquake.usgs.gov/research/earlywarning/images/sta... https://earthquake.usgs.gov/research/earlywarning/nextsteps.php https://earthquake.usgs.gov/research/earlywarning/nextsteps....
abcanthur 7y ago
I haven't lived in seismic areas much, but I was in central LA for both of these quakes. I was hoping for a simple Richter*distance (or d^.5, whatever may be appropriate) value to be reported. I realize that real effects are multivariate, but wouldn't that at least provide the maximum possible effects to report a magnitude-distance metric? Bc for a few million people I think the quake felt like a strong spin cycle in the next room , but we were told it was the biggest in decades.
- weaksauce 7y ago
  There is a government site that shows the intensity of each earthquake on a map like that. Where I was it was a 3 mmi
- Gibbon1 7y ago
  Yeah really depends one distance and local conditions. And sometime 'micro' local conditions. Friend of mine that lived in Oakland during the 89 earthquake mentioned seeing a 'line' of damaged buildings that snaked through a neighborhood. One or two houses on a block were wrecked. The houses across the street were also wrecked. Houses next to them were fine. Go the next street over same thing. He thinks that line followed an old creek bed that developers filled in. So those houses were built on mud overlain with poorly compacted fill. During the earthquake the mud liquefied and sloshed around and the fill settled. Flip side, friend in the Santa Cruz mountains a couple of miles from the epicenter. His house is built on top of a hard shale outcrop. His house suffered no damage at all.
  - DrScump 7y ago
    The weakness of poor fill was also demonstrated by the collapse of row houses in the Marina district of SF. One striking effect was the directionality of the damaging waves. Bookcases and such that were perpendicular to the waves from the hypocenter went over; those that were parallel were fine.
- bestnameever 7y ago
  Dr Lucy Jone's said it was around a 4.0 intensity in the Los Angeles area.
spuz 7y ago
Probably because the average Japanese person experiences a lot more earthquakes than the average American even those in the highest risk areas. It's much harder to get a feeling for a value on a particular earthquake scale if you only experience 2 in your lifetime.
- kelnos 7y ago
  If you live in California, you'll experience more than two earthquakes per year (hell, SoCal just had two reasonably strong ones over a span of two days). It's certainly enough to develop an intuition around relative amounts of shaking.
  - ma2rten 7y ago
    I live in California, I have never noticed them.
    - frizkie 7y ago
      Yeah I don't generally either. I live north of the Bay Area and the last quake I remember feeling there was the Napa one in 2014. I believe it was somewhere between a 5.5 and 6.0. I went to school in the LA Inland Empire area - there was a quake I felt last year there during class. It was really close but I'm pretty sure it was just short of 4.0. We have hundreds (thousands?) of quakes per year, but the likelihood your average resident feels a quake in any given year? I think it's low.
  - cj 7y ago
    I have lived in the bay area for 7 years (2012-2019). I have never felt an earthquake. I recall a few happening (from news reports, twitter), but I either didn't feel them or they happened at night while sleeping. The only time I've felt the ground shake was in the earthquake simulator at the California Academy of Science in SF :)
    - gonyea 7y ago
      The Hayward fault seems to have the most seismic activity lately. You'll feel them 2+ times a year in the East Bay--especially if you're in an older, multi-story building when it strikes.
HenryBemis 7y ago
I remember in my "lyceum" years (15-17) among many other geological studies we were taught the significance and uniqueness of the Richter Vs Mercalli scales. It always surprised me how in Europe you never hear of the Mercalli scale and its importance to assess. I assume it is (as some others mentioned below) the lack of the necessary wide-scale of sensors that need to be deployed throughout certain seismogenic areas that tend to be wide (e.g. majority of Italy, Greece). Good to know that Japan (not surprised though as they are more mature/experienced in certain areas) they still use fantastic "tool" called Mercalli.
ronnier 7y ago
I watched the news and it was mentioned several times.
SubiculumCode 7y ago
I am no expert, but perhaps it is because the Richter Scale was built specifically for quakes in California. https://en.wikipedia.org/wiki/Richter_magnitude_scale https://en.wikipedia.org/wiki/Richter_magnitude_scale
- Gibbon1 7y ago
  I think the 1906 earthquake was one or the first to be extensively scientifically documented. I've read recently that total estimated energy doesn't translate very well. California is a mass of faults and poorly consolidated rock.[1]. Apparently that dissipates the energy quickly and shaking drops off sharply with distance. Other parts of the world with large areas of solid bedrock shaking can extend for very long distances. The new Madrid earthquake was thought to be an 8+ magnitude originally. But more recent estimated put it at ~7.3.
peter303 7y ago
Your assessment is incorrect. The NEIC releases two intensity maps very quickly (1) 'Did you feel it?' based on internet crowd sourcing reports And (2) 'Shake Map' from instrumental readings.
- needle0 7y ago
  Well I didn't say they're not used, just not as much by everyday laypeople and the media. The article for this thread makes no mention, for instance, and out of the top 5 DuckDuckGo search result news articles for "ridgecrest quake" [1], only one of them contained the words "intensity" or "Mercalli". Mentions of shindo values in Japanese news are ubiquitous. [1] https://heavy.com/news/2019/07/ridgecrest-earthquake-damage-injuries/ https://heavy.com/news/2019/07/ridgecrest-earthquake-damage-... https://losangeles.cbslocal.com/2019/07/04/6-6m-quake-strikes-near-ridgecrest-in-kern-county/ https://losangeles.cbslocal.com/2019/07/04/6-6m-quake-strike... https://edition.cnn.com/us/live-news/earthquake-california-july-2019/index.html https://edition.cnn.com/us/live-news/earthquake-california-j... https://www.cbsnews.com/news/ridgecrest-earthquake-aftershock-recorded-today-2019-07-05/ https://www.cbsnews.com/news/ridgecrest-earthquake-aftershoc... https://www.latimes.com/local/lanow/la-me-ridgecrest-earthquake-size-magnitude-intensity-20190704-story.html https://www.latimes.com/local/lanow/la-me-ridgecrest-earthqu...

bribroder 7y ago

It might be a data collection problem--the JMA has deployed a pretty dense network of sensors over their entire territory, which makes sense given how geologically active it is. In fact the Earthquake Early Warning's "next steps" plan says "New sensors need to be added in California to shorten the CISN sensors spacing to approximately 12 miles to facilitate timely EEW. The shorter the station spacing, the smaller the blind zone will be because warnings can be issued faster." Check out this map comparison of the two networks: https://earthquake.usgs.gov/research/earlywarning/images/stationdensity.JPG https://earthquake.usgs.gov/research/earlywarning/images/sta... https://earthquake.usgs.gov/research/earlywarning/nextsteps.php https://earthquake.usgs.gov/research/earlywarning/nextsteps....

abcanthur 7y ago

I haven't lived in seismic areas much, but I was in central LA for both of these quakes. I was hoping for a simple Richter*distance (or d^.5, whatever may be appropriate) value to be reported. I realize that real effects are multivariate, but wouldn't that at least provide the maximum possible effects to report a magnitude-distance metric? Bc for a few million people I think the quake felt like a strong spin cycle in the next room , but we were told it was the biggest in decades.

weaksauce 7y ago
There is a government site that shows the intensity of each earthquake on a map like that. Where I was it was a 3 mmi
Gibbon1 7y ago
Yeah really depends one distance and local conditions. And sometime 'micro' local conditions. Friend of mine that lived in Oakland during the 89 earthquake mentioned seeing a 'line' of damaged buildings that snaked through a neighborhood. One or two houses on a block were wrecked. The houses across the street were also wrecked. Houses next to them were fine. Go the next street over same thing. He thinks that line followed an old creek bed that developers filled in. So those houses were built on mud overlain with poorly compacted fill. During the earthquake the mud liquefied and sloshed around and the fill settled. Flip side, friend in the Santa Cruz mountains a couple of miles from the epicenter. His house is built on top of a hard shale outcrop. His house suffered no damage at all.
- DrScump 7y ago
  The weakness of poor fill was also demonstrated by the collapse of row houses in the Marina district of SF. One striking effect was the directionality of the damaging waves. Bookcases and such that were perpendicular to the waves from the hypocenter went over; those that were parallel were fine.
bestnameever 7y ago
Dr Lucy Jone's said it was around a 4.0 intensity in the Los Angeles area.

spuz 7y ago

Probably because the average Japanese person experiences a lot more earthquakes than the average American even those in the highest risk areas. It's much harder to get a feeling for a value on a particular earthquake scale if you only experience 2 in your lifetime.

kelnos 7y ago
If you live in California, you'll experience more than two earthquakes per year (hell, SoCal just had two reasonably strong ones over a span of two days). It's certainly enough to develop an intuition around relative amounts of shaking.
- ma2rten 7y ago
  I live in California, I have never noticed them.
  - frizkie 7y ago
    Yeah I don't generally either. I live north of the Bay Area and the last quake I remember feeling there was the Napa one in 2014. I believe it was somewhere between a 5.5 and 6.0. I went to school in the LA Inland Empire area - there was a quake I felt last year there during class. It was really close but I'm pretty sure it was just short of 4.0. We have hundreds (thousands?) of quakes per year, but the likelihood your average resident feels a quake in any given year? I think it's low.
- cj 7y ago
  I have lived in the bay area for 7 years (2012-2019). I have never felt an earthquake. I recall a few happening (from news reports, twitter), but I either didn't feel them or they happened at night while sleeping. The only time I've felt the ground shake was in the earthquake simulator at the California Academy of Science in SF :)
  - gonyea 7y ago
    The Hayward fault seems to have the most seismic activity lately. You'll feel them 2+ times a year in the East Bay--especially if you're in an older, multi-story building when it strikes.

HenryBemis 7y ago

I remember in my "lyceum" years (15-17) among many other geological studies we were taught the significance and uniqueness of the Richter Vs Mercalli scales. It always surprised me how in Europe you never hear of the Mercalli scale and its importance to assess. I assume it is (as some others mentioned below) the lack of the necessary wide-scale of sensors that need to be deployed throughout certain seismogenic areas that tend to be wide (e.g. majority of Italy, Greece). Good to know that Japan (not surprised though as they are more mature/experienced in certain areas) they still use fantastic "tool" called Mercalli.

ronnier 7y ago

I watched the news and it was mentioned several times.

SubiculumCode 7y ago

I am no expert, but perhaps it is because the Richter Scale was built specifically for quakes in California. https://en.wikipedia.org/wiki/Richter_magnitude_scale https://en.wikipedia.org/wiki/Richter_magnitude_scale

Gibbon1 7y ago
I think the 1906 earthquake was one or the first to be extensively scientifically documented. I've read recently that total estimated energy doesn't translate very well. California is a mass of faults and poorly consolidated rock.[1]. Apparently that dissipates the energy quickly and shaking drops off sharply with distance. Other parts of the world with large areas of solid bedrock shaking can extend for very long distances. The new Madrid earthquake was thought to be an 8+ magnitude originally. But more recent estimated put it at ~7.3.

peter303 7y ago

Your assessment is incorrect. The NEIC releases two intensity maps very quickly (1) 'Did you feel it?' based on internet crowd sourcing reports And (2) 'Shake Map' from instrumental readings.

needle0 7y ago
Well I didn't say they're not used, just not as much by everyday laypeople and the media. The article for this thread makes no mention, for instance, and out of the top 5 DuckDuckGo search result news articles for "ridgecrest quake" [1], only one of them contained the words "intensity" or "Mercalli". Mentions of shindo values in Japanese news are ubiquitous. [1] https://heavy.com/news/2019/07/ridgecrest-earthquake-damage-injuries/ https://heavy.com/news/2019/07/ridgecrest-earthquake-damage-... https://losangeles.cbslocal.com/2019/07/04/6-6m-quake-strikes-near-ridgecrest-in-kern-county/ https://losangeles.cbslocal.com/2019/07/04/6-6m-quake-strike... https://edition.cnn.com/us/live-news/earthquake-california-july-2019/index.html https://edition.cnn.com/us/live-news/earthquake-california-j... https://www.cbsnews.com/news/ridgecrest-earthquake-aftershock-recorded-today-2019-07-05/ https://www.cbsnews.com/news/ridgecrest-earthquake-aftershoc... https://www.latimes.com/local/lanow/la-me-ridgecrest-earthquake-size-magnitude-intensity-20190704-story.html https://www.latimes.com/local/lanow/la-me-ridgecrest-earthqu...