soubriquet 0 Posted July 23, 2007 Author Share Posted July 23, 2007 The red squiggles are active faults. Link to post Share on other sites
muikabochi 208 Posted July 23, 2007 Share Posted July 23, 2007 Looks like there's a whole bunch of them on the Niigata/Nagano border there (just above the word I in ISTL). My guess is that area is the area within Tsunan, Myoko, Nagano city, Iiyama that kind of area. Nasty. Link to post Share on other sites
iiyamadude 6 Posted July 24, 2007 Share Posted July 24, 2007 Looks like they are centered below my house. Link to post Share on other sites
SirJibAlot 0 Posted July 24, 2007 Share Posted July 24, 2007 Just had a quake in Kanto - looks like a 4.4 out in Kanagawa. Spooked me! Link to post Share on other sites
Tubby Beaver 209 Posted July 25, 2007 Share Posted July 25, 2007 yeah apparently, but I didn't feel anything, I was down the beach Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 Originally Posted By: tsondaboy A Moment tensor solution always gives you 2 planes, like in the USGS pick. You can’t really say just by one solution, which is the plane that represents the fault. Usually the distribution of the aftershocks gives you a good idea of the geometry of the area that has slipped. The distribution up to now points to an East dipping thrust. Last night's NHK reported the aftershocks indicating a NW dipping fault. Me right Link to post Share on other sites
liver 0 Posted July 27, 2007 Share Posted July 27, 2007 I don't know what an earthquake feels like. Not sure I want to! Sounds terrifying. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 Not fun Link to post Share on other sites
liver 0 Posted July 27, 2007 Share Posted July 27, 2007 If you had to describe it, how would you? I'd be interested to hear! Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 It's frightening. And I live in an earthquake resistant building. Everything starts jumping around, and you have no idea how big it will be or how long it will last. Link to post Share on other sites
Tubby Beaver 209 Posted July 27, 2007 Share Posted July 27, 2007 It sometimes starts like when you get up to fast, things seem to move but your brain is telling you that its impossible, then the pots and pans start rattling and shit REALLY starts to move! Link to post Share on other sites
tsondaboy 0 Posted July 27, 2007 Share Posted July 27, 2007 Originally Posted By: soubriquet Last night's NHK reported the aftershocks indicating a NW dipping fault. Me right I didnt see the NHKs report last night so cant comment on that, but this is the after shock distribution up to now. And how it is distributed in time. Red circle main shock M6.8, purple circle largest aftershock M5.8 (up to now). As I said, its too early to jump into conclusions. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 Thanks. Certainly looks like a SE dip. What do the red and blue parallelograms on the cross sections mean? Why would NHK report something definitive? They quoted the information as coming from the JMA. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 What is the error in the depth estimates? Link to post Share on other sites
tsondaboy 0 Posted July 27, 2007 Share Posted July 27, 2007 JMA is known for not being accurate in their estimations, not only of hypocenters but also about weather and staff. The red and blue parallelograms in the cross sections are the depth extensions of the NW dipping faults in the area. They don’t really fit with the hypocenters distribution as you can see. The main problem is that all the data we have up to now are from land based on-line stations to the SE. In order to accurately determine the hypocenters we need some travel time data from stations to the NW. From what I know, they are deploying OBSs (Ocean Bottom Seismometers) in the area to the NW, but it will take at least 2 month to collect the data and more than that to process them. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 Thanks. I'm not familiar with thrust tectonics. All my seismic experience is rift/oil related stuff. If those aftershocks are reasonably well constrained, then clearly it's a fairly complex fault system. Do you use an approximation for time to distance/depth, or can you calculate the velocities? Link to post Share on other sites
tsondaboy 0 Posted July 27, 2007 Share Posted July 27, 2007 Calculating the 3D distribution of the Vp,Vs velocities in the crust/upper mantle is what I do for my Phd. It is a process that takes lots of time and requires a considerable amount of data. For reasons of simplicity and speed, we determine the hypocenters using an average 1D layered model. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 RhightyO. Thanks. You'd better get the pocket calculator out and get cracking then Link to post Share on other sites
muikabochi 208 Posted July 27, 2007 Share Posted July 27, 2007 In my (unfortunately considerable) experience there are a few different types of feeling. All of them most definitely not nice and scary. Main big earthquakes happen suddenly and of course you don't know to expect them or are prepared for them coming. The two big big ones I have experienced were violent, sudden (in that it didn't start with gentle shaking) and more than anything it was just a case of "lets survive" going on in your head. Heart nearly exploding after the fact. Once the main one is gone the aftershocks start. I think people would agree that in some ways these are wose. They may not be as strong but they go on and on and you are half expecting them. So you are living in fear. Often less sudden you can almost hear them coming, like a low grumbling truck approaching sound. Then the shaking and the wondering how big will it get. I found them to be psychologically very damaging. With the one we had 3 years ago, there were a crazy number of aftershocks. Link to post Share on other sites
soubriquet 0 Posted July 27, 2007 Author Share Posted July 27, 2007 SJ1 made the same observation re aftershocks. He didn't like them at all. Earthquakes generate a number of different wave types. They move at different velocities. When you're up nice and close, the P waves and the S waves will arrive tightly bunched. Lucky you. We had several (10-20?) seconds of fairly gentle shaking before the S waves came with a thump. P-wave in rock: 3.5-6.5 km/sec S-wave in rock: 1.8-3.8 km/sec (source Parasnis) Link to post Share on other sites
muikabochi 208 Posted July 27, 2007 Share Posted July 27, 2007 Yes we had a similar experience, living so close. I think most people will say that. You're just sitting there expecting all those aftershock earthquakes, it's not nice. On alert every time a car or truck comes by. Link to post Share on other sites
sanjo 2 Posted July 28, 2007 Share Posted July 28, 2007 I find it really difficult to describe, don't think you can truly understand the scariness of it until you actually experience it. Not that I would wish that on anyone. Link to post Share on other sites
SirJibAlot 0 Posted July 28, 2007 Share Posted July 28, 2007 Imagine you are sleeping in your bed, you open you eyes and there is a large African man with a bone in his nose and a knife in his hand and he doesn't look happy. That is probably the best way to descibe the unexpected, sudden shock and TERROR of an earthquake and the accompanying fear for your life. Link to post Share on other sites
giggsy 0 Posted August 13, 2007 Share Posted August 13, 2007 There was an earthquake in Manchester the other day. 2.5 magnitude apparently. I didn't feel anything but some people in the office were a bit spooked for a few minutes. Didn't even make the local news that night! Link to post Share on other sites
rach 1 Posted August 13, 2007 Share Posted August 13, 2007 I read about that. No-one predict it? Link to post Share on other sites
Recommended Posts