soubriquet 0 Posted May 22, 2011 Author Share Posted May 22, 2011 Tricky questions, grasshopper. I've done some more scratching around and had a bit of a think. Magnitude is the amount of energy released at the hypocentre. It's interesting from an academic perspective, it's what I covered at uni, but it doesn't tell us much about what is happening on the ground. Shindo, PGA (Peak Ground Acceleration) and Mercalli scales are measures of acceleration, and are what is important for an engineer to design a structure. I can find wikidata on Shindo and PGA, but I'm having trouble reconciling the numbers. Shindo 6+ gives a peak acceleration of 3.15–4.00 m/s². The PGA scale gives acceleration in g. Magnitude VIII is 0.35-0.65g, which equates to about 3.3-6.5 m/s². Those numbers are nuts. Sustained over one second we get greater than 3 metres of ground displacement. Fortunately P-wave frequency is about 20Hz, meaning 40 accelerations per second. That gives us something less than 75mm displacement each way per cycle. It's still a lot: no wonder stuff leaps around. So, I'll requalify M8 as M VIII Link to post Share on other sites
muikabochi 208 Posted May 22, 2011 Share Posted May 22, 2011 Well, you have totally lost me there! Link to post Share on other sites
soubriquet 0 Posted May 22, 2011 Author Share Posted May 22, 2011 Oh no. I'll say thanks anyway, because the I'd never really tried to nut out the difference between magnitude and intensity. I've been looking but not seeing. Think of it this way. At zero seconds, you are standing at a point on the ground. One second later, that point is 3 metres from where you were standing. That's acceleration, and how intensity is measured. Except, the ground isn't moving in one direction, its shaking back and forth, 20 or so times a second. It's going 75mm in one direction, then coming back another 75mm (that's an overestimate, but I'm not going to get into the calculus). M VIII or Shindo 6+. Shindo starts at zero, not one, hence 10 divisions. Link to post Share on other sites
muikabochi 208 Posted May 23, 2011 Share Posted May 23, 2011 Originally Posted By: soubriquet Think of it this way. At zero seconds, you are standing at a point on the ground. One second later, that point is 3 metres from where you were standing. That's acceleration, and how intensity is measured. Except, the ground isn't moving in one direction, its shaking back and forth, 20 or so times a second. It's going 75mm in one direction, then coming back another 75mm (that's an overestimate, but I'm not going to get into the calculus). M VIII or Shindo 6+. Oh dear, I think I'd rather not think about it. I know what each of those the scale feels like apart from those top two, so I think I'll just keep it at that. Link to post Share on other sites
grungy-gonads 54 Posted May 24, 2011 Share Posted May 24, 2011 Did (are) you get feel many of the aftershocks over where you are soubs? A bit too far away for many biggies perhaps, you are closer to the west coast than the east aren't you? Link to post Share on other sites
soubriquet 0 Posted May 24, 2011 Author Share Posted May 24, 2011 We're about 70km WNW of Sendai, pretty much halfway between each coast. Heaps of aftershocks, probably hourly for at least a month. We felt the Niigata quake, and the really big aftershock off Onagawa came through at 5-, same as the main quake, except we had a lot of ground roll that time. That time the power was only off for a day, and the water for 2. The memsahib and I regularly count our blessings, and we are truly blessed here. It's a lovely part of the country. The ground is fertile, we get plenty of sun and rain. We don't get big earthquakes or typhoons. The only irritation is the volume of snow, but that's a small thing in the bigger scheme. Link to post Share on other sites
soubriquet 0 Posted May 24, 2011 Author Share Posted May 24, 2011 I took this on the way home from work yesterday. Chokai San in the distance. Here's where I live, the valley mid distance. Farms, forests and snow capped mountains. The rivers are clean too. Link to post Share on other sites
Tubby Beaver 209 Posted May 24, 2011 Share Posted May 24, 2011 wow!! Haven't seen fish like that in rivers over here. Are there swimming spots nearby? Link to post Share on other sites
soubriquet 0 Posted May 24, 2011 Author Share Posted May 24, 2011 Yes there are. There's one about 5km from here, with a park and some barbecues. I just go to the local weir to enjoy a beer and dangle my feet in the water on a hot day. There's heaps of fishing. Link to post Share on other sites
Tubby Beaver 209 Posted May 24, 2011 Share Posted May 24, 2011 I wish there was that round here......I'd trade my beach-side town for a nice riverside swimming spot anyday Link to post Share on other sites
soubriquet 0 Posted May 24, 2011 Author Share Posted May 24, 2011 Here's where I go, I was standing on the weir. No problem swimming here, but you might upset the locals. Link to post Share on other sites
brit-gob 9 Posted May 25, 2011 Share Posted May 25, 2011 How's it going with the kids, soubs? Hope you don't mind asking. Link to post Share on other sites
soubriquet 0 Posted May 25, 2011 Author Share Posted May 25, 2011 Not at all brit-gob. Time has done its healing. They've grown up, and can and do travel independently to visit. No1 son has finished school. He's taking a gap year (sensible lad) and will be going to uni next year to study architecture. No 2 son has been on a mission ever since he started to crawl. He's found that mission and is going to join the RAAF whenever. He's in the cadets and learning to fly. Also all the other stuff: discipline, teamwork, bushcraft, washing ironing and sewing. They are good lads. I'm very proud of them both. Link to post Share on other sites
sunrise 0 Posted May 25, 2011 Share Posted May 25, 2011 Hey, I'm so glad to hear about your boys, Soub! Link to post Share on other sites
soubriquet 0 Posted May 25, 2011 Author Share Posted May 25, 2011 Hello sunrise. Nice to hear from you. I hope life and music are treating you well. I know my way around Zao a bit better now. You should come for another visit, but pick a weekend with better weather Link to post Share on other sites
HelperElfMissy 42 Posted May 25, 2011 Share Posted May 25, 2011 Originally Posted By: soubriquet Not at all brit-gob. Time has done its healing. They've grown up, and can and do travel independently to visit. No1 son has finished school. He's taking a gap year (sensible lad) and will be going to uni next year to study architecture. No 2 son has been on a mission ever since he started to crawl. He's found that mission and is going to join the RAAF whenever. He's in the cadets and learning to fly. Also all the other stuff: discipline, teamwork, bushcraft, washing ironing and sewing. They are good lads. I'm very proud of them both. Excellent outcomes Good news. Link to post Share on other sites
soubriquet 0 Posted May 25, 2011 Author Share Posted May 25, 2011 Thanks mamabear. No1 will be at UWA, and is thinking of moving in with a friend in Nedlands. Say hello if you see him Link to post Share on other sites
HelperElfMissy 42 Posted May 25, 2011 Share Posted May 25, 2011 Originally Posted By: soubriquet Thanks mamabear. No1 will be at UWA, and is thinking of moving in with a friend in Nedlands. Say hello if you see him He'll be just down the road from me. In fact half my life (slight exaggeration) is at UWA at the moment. #3 son is training in the Water Polo pool there 4 x week. Link to post Share on other sites
sunrise 0 Posted May 25, 2011 Share Posted May 25, 2011 Yeh Soubs, better weather next time, eh! If I'm ever up your way again I'll be sure to let you know! Link to post Share on other sites
sunrise 0 Posted May 25, 2011 Share Posted May 25, 2011 And thanks, life seems to be settling down again, with lots of music on the boil Link to post Share on other sites
soubriquet 0 Posted May 25, 2011 Author Share Posted May 25, 2011 Nedlands baths used to be a ramshackle timber structure built in the Swan at the end of a long walkway. The water was about 6 feet deep. Everything was covered in barnacles, and my abiding memory was of swimming in jellyfish. That was in about 1958. Tough we were in those days. Link to post Share on other sites
HelperElfMissy 42 Posted May 25, 2011 Share Posted May 25, 2011 Originally Posted By: soubriquet Nedlands baths used to be a ramshackle timber structure built in the Swan at the end of a long walkway. The water was about 6 feet deep. Everything was covered in barnacles, and my abiding memory was of swimming in jellyfish. That was in about 1958. Tough we were in those days. Far cry from for the rather well heated (albeit outdoor) pool these kids inhabit. I have fond memories of Bicton Baths Soubs - tough old buggers we are Link to post Share on other sites
Tubby Beaver 209 Posted May 25, 2011 Share Posted May 25, 2011 tough?? You've never swam in the sea-pool at Arbroath or Stonehaven off the east coast of Scotland! North Sea is frigid at best! separates the wheat from the chaff (and a lot bloody more) I can tell ya! Link to post Share on other sites
HelperElfMissy 42 Posted May 26, 2011 Share Posted May 26, 2011 Originally Posted By: Tubby Beaver tough?? You've never swam in the sea-pool at Arbroath or Stonehaven off the east coast of Scotland! North Sea is frigid at best! separates the wheat from the chaff (and a lot bloody more) I can tell ya! Righto Tubby guy, you are ON! Just added to my Bucket List Link to post Share on other sites
soubriquet 0 Posted May 26, 2011 Author Share Posted May 26, 2011 Correct. The North Sea is freezing. I've done my North Sea time at Cromer. A lot further south than Scotland, but still cold. The Southern Ocean isn't exactly warm though, is it mamabear? Link to post Share on other sites
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