On Sep 10, 2010, at 5:24 PM, Larry Colen wrote: > After our little 7.1 back in '89, one of the games I'd play was guessing the > distance and magnitude of the aftershocks. The delta-T between the p-waves > and the t-waves, along with the sharpness of the movement would give me a > pretty good idea of the distance. I'd use that distance as a fudge factor on > the intensity*time and guess the magnitude. By the time we stopped having > aftershocks, my butt was a fairly well calibrated seismograph.
Interesting :) I thought I was guessing about right but many of the aftershocks are being located within a couple of miles of my house. For a given shake I find I need to subtract about 1 from my estimate of the magnitude. But half the aftershocks are coming from the other end of the fault, maybe 30 miles away. They're all very shallow as well so the local ones are VERY sharp. They are definitely reducing in frequency. I saw a good graphic in a news article today... http://www.stuff.co.nz/national/canterbury-earthquake/4114666/Quake-Aftershocks-for-weeks Just found there's a wikipedia page about our quake. Never thought to look... http://en.wikipedia.org/wiki/2010_Canterbury_earthquake > Good luck, try to enjoy the ride. I got out of the house today and that's really helped a lot. I've been cooped up in here for most of the week, spending the daylight hours alone and trying to work. I went for a 2hr walk in the morning, then I went for a ride on my new bike (its first ride, it's only been a week). Found some fairly substantial cracking on a road that I've been riding in the mornings lately. Didn't take a camera, sorry. Then after lunch I managed to get into the city and pick up my commuter bike. Major milestone there and another weight off my mind as I had no idea what state it was in (exactly as I left it). Overall I was really surprised by what I saw in town. After I got back I was a complete zombie so I took our bean bag out into the sun and had a snooze. Despite the media photos, the CBD looks almost totally fine. Standing in Cathedral Square, I could see a bit of cosmetic cracking at the top of the facade of the building that houses the city aquarium. Some of the paving stones looked a little lumpy in one place but that could have been caused by food vendors parking heavy stuff on them. Other than that, nothing. The cathedral showed no evidence of damage that I could see. Same goes for the old post office building. All the recent strengthening work will have saved many of our historic buildings. There are still a few streets blocked so I couldn't see much there, and I know a couple of buildings are being demolished, but I really struggled to find much in the way of obvious damage. I didn't see any red placards (which says a building is off-limits). I haven't downloaded the pics from the camera yet but I'll have a look and put a couple up later. Having said that, a couple of suburbs have been hit hard, and so has the town of Kaiapoi. They were affected pretty badly by liquefaction and a lot of houses are being condemned after their foundations have been compromised. Some areas will need their sewer system totally rebuilt and the residents will be stuck with portaloos for a while yet. > One thing that I learned is that it is good to have a contact number that is > out of the local region. During an emergency, nobody can dial into any local > numbers, but it's easy to call someone out of the area. So have a relative, > or close friend who lives at least a few hundred klicks, or miles away that > you can have people call in case of an emergency (quake, flood etc.) in your > area. I didn't think of that, it makes sense as the local exchanges would be overloaded and calling a local number would tie up two connections. Both our fathers live out of town so we should be OK. Note the telephone service suffered no interruptions for us. The cell networks were borderline and they were asking people to send text messages instead of making voice calls whenever possible. The power outages caused some cellphone sites to cut out when their backup batteries ran out, but we didn't notice any problems. I still find it utterly amazing how well our city withstood this disaster. It certainly won't be causing our incumbent mayor any problems in the upcoming local-body elections. He's going to romp in. He has been absolutely outstanding in his response and his communication & handling of the media throughout. Cheers, Dave -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
