tag:blogger.com,1999:blog-5337555368793819627.post1349749299667477026..comments2023-06-07T09:04:36.390-04:00Comments on More Grumbine Science: Earthquake followupRobert Grumbinehttp://www.blogger.com/profile/10783453972811796911noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-5337555368793819627.post-28350219443076432322011-08-31T15:02:55.677-04:002011-08-31T15:02:55.677-04:00:-) Yes, New Madrid -- last significantly active ...:-) Yes, New Madrid -- last significantly active over 100 years ago. Of course one day it will be active again. But aside from that, the midwest doesn't see much over 4.5, which was too weak for me to feel even from close range. See http://earthquake.usgs.gov/earthquakes/states/historical_state.php for a state by state listing, in which New Madrid gets a listing to itself.<br /><br />Andy: Thanks for the elaborations. I'll hope a Texas geologist shows up to shed light on their peculiar quake response.Robert Grumbinehttps://www.blogger.com/profile/10783453972811796911noreply@blogger.comtag:blogger.com,1999:blog-5337555368793819627.post-72908014029162382722011-08-31T14:53:45.806-04:002011-08-31T14:53:45.806-04:00you see an enormous number of sensors in the Midwe...<i>you see an enormous number of sensors in the Midwest ... These are areas not known for seismic activity</i><br /><br />Is joke, yes? New Madrid?Bayesian Bouffant, FCDnoreply@blogger.comtag:blogger.com,1999:blog-5337555368793819627.post-39628760905368769412011-08-30T22:43:21.961-04:002011-08-30T22:43:21.961-04:00The first waves to arrive are The P waves (regular...The first waves to arrive are The P waves (regular acoustic waves) that follow the quickest but not the shortest route through the crust and mantle. The biggest amplitude arrivals are the PcP waves that are reflected off the liquid core of the Earth. <br /><br />The waves that arrive at about 10 minutes are probably Rayleigh (surface waves) that travel at about 3 km/s. They are subject to scattering, reflections and so on in the shallow geology, so they appear noisy compared to the other waves. They can be high amplitude because they spread out in only two dimensions, instead of three for the body waves. <br /><br />Why specifically they are relatively higher amplitude in Texas relative to further north is unknown to me but I'd guess it has something to do with the near surface geology of the Eastern US.Andy Shttps://www.blogger.com/profile/16313161977123410684noreply@blogger.com