I was looking at the usgs data last night, so it is quite nice to see somebody else made a visualization of the data. I looked at usgs, and was quite surprised to see there were over 100 >5 magnitude earthquakes off the coast of japan in the past week. Most seemed to be relatively shallow (10-20km), so i can't imagine what it must be like there right now. This isn't something I've read about in the papers, and I can't imagine why not. A single one of these aftershocks would be noteworthy in Seattle, and it appears these are hapening nearly every hour. Incredible.
Not just nearly every hour, around every 20 minutes there's an aftershock. Most of which would be a magnitude that'd make the news here in the US no matter where it happened. It's just mind boggling that there's been over 500 of them now and it's not really slowing it seems.
As NZ_Matt pointed out, most of the quakes's epicenters are offshore. The strength of the shake decreases rapidly with distance. In Tokyo it's still bad but not as bad as it might appear on the map. Sometimes it's like this:
A: "So we need to add one table to the database and"
B: "Wait."
A: "What?"
B: "It's shaking."
A: "Oh, is it? ... Ah, yeah"
B: "OK now. So what about the backups?"
On the other hand, the bigger aftershocks were grade 3 or 4 (in the Japanese scale) in Tokyo, which ranges from "shaking noticeably" to "shaking quite a lot". Personally, I don't feel scared anymore because I'm pretty sure both my apartment and my office won't crumble. Still, it's quite stressful.
Oh, you probably haven't read it in the (English-language) papers because they're too busy talking about the impending "nuclear winter".
The destruction from the earthquake itself could've been a lot worse in Japan if the epicenter was closer to Japan and not 200km offshore. This map shows that the shaking in Japan was not of a destructive intensity in most areas. http://earthquake.usgs.gov/earthquakes/shakemap/global/shake...
I made a similar map the other day for the LA Times: http://lat.ms/gJWWEK. Starts Thursday at the 7.2, and has every fore- and aftershock magnitude 5+ (until late yesterday, I need to update it).
The nice thing about this guy's map is that the circles are huge, and they fade out.
To put those values in scale (something few radiation graphs do, in my experience, especially when dealing with anything with the word "nuclear" in it):
The normal value at the highest location is about 1000 nGy, with a spurt at double that for a few hours. Which means it takes 1400 hours to equal an abdominal Xray - 58.3 days. Not good, but people react to news of things like this as if they're expecting to grow a third arm if they don't have a lead bunker to hide in now. The next highest areas are 1/10th that, meaning it'd take about a year and a half to equal a single medical Xray, barring whatever info comes in for the N/A areas.
Impressive. My only gripe is that I paused it on the 9M quake and zoomed out to look at the 'reach' of it, but hovering the mouse over the quake in the list on the right displays the quake as if it were at the original zoom level (i.e. doesn't take zoom out/in into account). That's unfortunate seeing as the 9M quake goes off the map on the default zoom level.
I don't think the radii of the circles actually correspond to a particular land area. How would one measure the "extent" of an earthquake, anyway? It's not like they have well-defined, circular bounds.
More likely, the circles are just sized in proportion to the magnitude of the quake, to give you a visual sense of scale.
You can move the map without zooming and the circles follow.
I think the circles are quite proportional. I have a friend of a friend in Osaka who said they did feel the 9.0M one all the way down in Osaka so that circle is correct.
Edit: Actually I had zoomed in a level. I think zooming in one level is a little more accurate. I really don't think people in Korea or Eastern Russia felt it.
By the way, it's part of their weather website and existed way before this disaster. It shows the last earthquake, the magnitude at the epicenter and a list of the magnitudes at surrounding areas. There's also a list of past quakes.
we feel every single earthquake that is on this map.
we live in Nikko Japan and operate a hostel http://zenhostel.jp (500 meters above sea level), 160 km southwest of the Fukushima Nuclear Reactor and 100 km due north of Tokyo.
the fact that the epicenters are offshore is meaningless to the fact that the mountains here in Nikko are shaking with each of those earthquakes.
I have felt 3 earthquakes in the time it took me to write this message.
i was making a video of my brother at the Unesco world heritage area when the 9.0 Tohoku earthquake struck;
http://youtu.be/tH1Y0kMcQwM?a
This is horrifying. I'd be curious to see historical data from other large earthquakes, i.e. is this typical for an earthquake of this magnitude (of which I realize are few) or is this a further geological anomaly?
Yes, I was in Tokyo this past weekend when the big one happened. I was feeling aftershocks all weekend long. What I didn't know was just how close the big 7.9 aftershock was to Tokyo.
The earthquake's distance beneath the Earth's surface, which I believe starts at 0km on the ocean floor for the purposes of these measurements -- meaning, the water has nothing to do with it and the word depth is a coincidence. That confused me at first.
"The depth where the earthquake begins to rupture. This depth may be relative to mean sea-level or the average elevation of the seismic stations which provided arrival-time data for the earthquake location. The choice of reference depth is dependent on the method used to locate the earthquake. Sometimes when depth is poorly constrained by available seismic data, the location program will set the depth at a fixed value. For example, 33 km is often used as a default depth for earthquakes determined to be shallow, but whose depth is not satisfactorily determined by the data, whereas default depths of 5 or 10 km are often used in mid-continental areas and on mid-ocean ridges since earthquakes in these areas are usually shallower than 33 km."
I think it needs a clarification.. As a gamer, a map is basically the virtual place where you play and quake is a famous shooter game. So, basically, I thought that "japan quake map" was a map for the quake game.
It, by no means, was an insult/bad joke about the current situation in Japan as we all know how terrible it is.
Here's an explanation of the quake's inverse square rule describing the relationship of the force experienced to the distance away from it: http://news.ycombinator.com/item?id=2332793
