Re: [time-nuts] OT: NZ Christchurch member
Hi: The Richter method of analyzing earthquakes is based on what can be learned from a simple seismometer. For example by looking at the time difference between the P wave and the main shaking you can determine how far away the epicenter is located. The Richter number depends on the peak of the main shaking. But the energy depends on the integral of the magnitude of the shaking over the time it lasts. The damage is proportional to the total energy not it's peak. The public is used to hearing the Richter number even though it does not really describe the damage level. For example I had just left work when the Loma Prieta quake happened and was standing in front of the building watching the wall sized windows oil canning. With each cycle the window displacement was getting larger. If the quake had lasted about 30 second longer all the windows would have exploded, either with glass going into the building or coming at those of us standing in in front. We started to get on the ground to get some protection, but then the quake stopped. http://www.prc68.com/I/Seismometer.shtml Have Fun, Brooke Clarke http://www.PRC68.com William H. Fite wrote: For meteorologists and geologists, the Richter scale has a carefully defined meaning and is used only for purposes where that definition fits. This per a friend of mine who does seismic stuff for NOAA: Him: The Richter number means something very specific to us and something quite different to the media. Actually, the Richter doesn't have a great deal of analytical value to us. You can say, this is a Category Four hurricane but that really tells you very little about what is going on in the storm. Richter is like that. Me: You're saying that the Richter is a poor predictor of surface disruption? Him: Well, obviously a 9 will be expected to do much more damage than a 6 but it is at best a very rough indicator. The location of the epicenter and a dozen other factors play into it. Me: So how do you assess the damage potential? Him: Lots of people think we still rely mainly on the old pendulum-and-stylus seismographs from the 1930s. Actually, we take a great many measurements in addition to seismometry. But when it comes to assessing the damage, we go outside and look, just like the TV stations do. And his final comment: By the way, did you know that when the shuttle launches we capture that on virtually every strain guage seismometer in the country? I found that interesting. On Thu, Feb 24, 2011 at 10:56 PM, jimlux wrote: On 2/24/11 5:23 PM, Bob Bownes wrote: What is the conversion factor for Richter to dBm? :) Bob As a guy with degrees in geology and EE. I really should know this...:) Especially since both are log scales.. The problem is that Richter is log magnitude displacement on a particular kind of seismometer (which is sort of a low pass filter) and dBm is log power. However, there should be some sort of scale factor that converts it. I think it's energy goes as amplitude^1.5. there's also a scale factor for how far the seismograph is from the epicenter. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
The last 'modern' seismometers I worked with (as an undergrad in the early 80's) were all three axis laser interferometry based. I'm sure they've gotten a bit better since then. Not only could we pick up a shuttle launch from 1,400 miles away, we could pick up frat parties from across town on the old strain gauge monster at the top of the hill. :) It was one of my first exposures to filtering actually. As your friend said, 'Richter' is not actually used by seismologists anymore, they use the moment magnitude scale for larger quakes, which, while similar, is different. It's more about energy released than about motion. Back to your regularly scheduled discussion. Bob On Fri, Feb 25, 2011 at 11:09 AM, jimlux wrote: > On 2/25/11 7:55 AM, Poul-Henning Kamp wrote: >> >> In message, >> "Wil >> liam H. Fite" writes: >> >>> Me: You're saying that the Richter is a poor predictor of surface >>> disruption? >> >> For damage assement you really need a vector-version of richter, >> vertical does a lot more damage than horizontal on average. >> > > > Yes.. I doubt anyone still uses the torsion seismometer Richter used, > although more modern scales (moment magnitude, etc.) still relate back (e.g. > they set the calibration to match for some notional set of events).. > > That way, people have an idea... A Magnitude 3 earthquake within a few tens > of km of me will be noticeable, if it's quiet. A magnitude 4 will be very > noticeable, and a 5 will be exciting. A 6 will wake you up in the middle of > the night. I'd compare it to something like Mohs hardness, except actually > with a quantitative basis. (People who work with material properties like > hardness use other scales anyway) > > It's a "roughly quantitative" measure of energy release, in the same sense > that kilotons are for explosions. It's like that whole "cup of gasoline: > dynamite" comparison.. it's the rate of energy (e.g. power) that creates the > qualitative difference between running my camping stove and blasting. > > We do the same thing in time-nuttery.. we use log scales to talk about > performance.. dBc/Hz for phase noise, and really, just the exponent to talk > about ADEV. (nobody gets excited about the difference between 1.1E-13 and > 1.5E-13... but the difference between 1E-11 and 1E-15 is worth talking > about) > > Maybe we should start promulgating dBallan? > > And maybe get an SI unit... The "Allan", although since the fractional > frequency error is dimensionless > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
On 2/25/11 7:55 AM, Poul-Henning Kamp wrote: In message, "Wil liam H. Fite" writes: Me: You're saying that the Richter is a poor predictor of surface disruption? For damage assement you really need a vector-version of richter, vertical does a lot more damage than horizontal on average. Yes.. I doubt anyone still uses the torsion seismometer Richter used, although more modern scales (moment magnitude, etc.) still relate back (e.g. they set the calibration to match for some notional set of events).. That way, people have an idea... A Magnitude 3 earthquake within a few tens of km of me will be noticeable, if it's quiet. A magnitude 4 will be very noticeable, and a 5 will be exciting. A 6 will wake you up in the middle of the night. I'd compare it to something like Mohs hardness, except actually with a quantitative basis. (People who work with material properties like hardness use other scales anyway) It's a "roughly quantitative" measure of energy release, in the same sense that kilotons are for explosions. It's like that whole "cup of gasoline: dynamite" comparison.. it's the rate of energy (e.g. power) that creates the qualitative difference between running my camping stove and blasting. We do the same thing in time-nuttery.. we use log scales to talk about performance.. dBc/Hz for phase noise, and really, just the exponent to talk about ADEV. (nobody gets excited about the difference between 1.1E-13 and 1.5E-13... but the difference between 1E-11 and 1E-15 is worth talking about) Maybe we should start promulgating dBallan? And maybe get an SI unit... The "Allan", although since the fractional frequency error is dimensionless ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
In message , "Wil liam H. Fite" writes: >Me: You're saying that the Richter is a poor predictor of surface >disruption? For damage assement you really need a vector-version of richter, vertical does a lot more damage than horizontal on average. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
For meteorologists and geologists, the Richter scale has a carefully defined meaning and is used only for purposes where that definition fits. This per a friend of mine who does seismic stuff for NOAA: Him: The Richter number means something very specific to us and something quite different to the media. Actually, the Richter doesn't have a great deal of analytical value to us. You can say, this is a Category Four hurricane but that really tells you very little about what is going on in the storm. Richter is like that. Me: You're saying that the Richter is a poor predictor of surface disruption? Him: Well, obviously a 9 will be expected to do much more damage than a 6 but it is at best a very rough indicator. The location of the epicenter and a dozen other factors play into it. Me: So how do you assess the damage potential? Him: Lots of people think we still rely mainly on the old pendulum-and-stylus seismographs from the 1930s. Actually, we take a great many measurements in addition to seismometry. But when it comes to assessing the damage, we go outside and look, just like the TV stations do. And his final comment: By the way, did you know that when the shuttle launches we capture that on virtually every strain guage seismometer in the country? I found that interesting. On Thu, Feb 24, 2011 at 10:56 PM, jimlux wrote: > On 2/24/11 5:23 PM, Bob Bownes wrote: > >> What is the conversion factor for Richter to dBm? :) >> >> Bob >> As a guy with degrees in geology and EE. I really should know this...:) >> >> >> > Especially since both are log scales.. > > The problem is that Richter is log magnitude displacement on a particular > kind of seismometer (which is sort of a low pass filter) and dBm is log > power. However, there should be some sort of scale factor that converts it. > > I think it's energy goes as amplitude^1.5. there's also a scale factor for > how far the seismograph is from the epicenter. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
On 2/24/11 5:23 PM, Bob Bownes wrote: What is the conversion factor for Richter to dBm? :) Bob As a guy with degrees in geology and EE. I really should know this...:) Especially since both are log scales.. The problem is that Richter is log magnitude displacement on a particular kind of seismometer (which is sort of a low pass filter) and dBm is log power. However, there should be some sort of scale factor that converts it. I think it's energy goes as amplitude^1.5. there's also a scale factor for how far the seismograph is from the epicenter. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
What is the conversion factor for Richter to dBm? :) Bob As a guy with degrees in geology and EE. I really should know this...:) On Thu, Feb 24, 2011 at 8:11 PM, Magnus Danielson wrote: > On 24/02/11 10:38, Steve Rooke wrote: >> >> I heard he was still shaking :) > > Did he get any amazing waveforms out of mother earths shaker-table? > > PS. Happy to hear you are alright and still has a sense of humor intact. > > Cheers, > Magnus > >> Cheers, Steve >> >> On 24/02/2011, Raj wrote: >>> >>> Anyone hear from Time-Nut Steve Rooke from Christchurch ? >>> >>> Cheers >>> >>> -- >>> Raj, VU2ZAP >>> Bangalore, India. >>> >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> >> > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
On 24/02/11 10:38, Steve Rooke wrote: I heard he was still shaking :) Did he get any amazing waveforms out of mother earths shaker-table? PS. Happy to hear you are alright and still has a sense of humor intact. Cheers, Magnus Cheers, Steve On 24/02/2011, Raj wrote: Anyone hear from Time-Nut Steve Rooke from Christchurch ? Cheers -- Raj, VU2ZAP Bangalore, India. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
Steve, Isn't Bruce Griffiths in your area ? I am wondering how he is doing ? BillWB6BNQ ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] OT: NZ Christchurch member
I heard he was still shaking :) Cheers, Steve On 24/02/2011, Raj wrote: > Anyone hear from Time-Nut Steve Rooke from Christchurch ? > > Cheers > > -- > Raj, VU2ZAP > Bangalore, India. > > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > -- Steve Rooke - ZL3TUV & G8KVD The only reason for time is so that everything doesn't happen at once. - Einstein ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] OT: NZ Christchurch member
Anyone hear from Time-Nut Steve Rooke from Christchurch ? Cheers -- Raj, VU2ZAP Bangalore, India. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
