M3.5 – 4km ESE of Nelsonville, Ohio

I received an email notification this afternoon that a Magnitude 3.5 earthquake occurred east southeast of Nelsonville, Ohio just before 1:00 pm local time.  My heligraph has been very noisy so I couldn’t really see any signal even though the epicenter was only 79 miles south of Millersburg where I am located.  When I zoomed in on the trace though I could see an excursion at about the right time.  Just to be sure I checked a nearby helicorder located at Kent State University Branch campus in New Philadelphia, one of the OhioSeis network stations.  It showed the first arrival at about 20 seconds past 18:00 UTC, the same as mine. There were 373 felt reports by mid afternoon mostly in southeastern Ohio..

 

Postscript (April 27, 2014) :

In an email exchange with another amateur seismologist, he had included a link to additional information on using the AmaSeis software.  As I read some of the entries I found an article on analyzing local events so I applied it to this event in Nelsonville, only 79 miles south of my seismograph.  One of the characteristics of local earthquakes is that they have a higher frequency content than more distant teleseismic events. These can be extracted by using a high pass filter on the signal.  Following the lead of the article, I applied a 1.2 second high-pass filter twice to the Nelsonville signal with the results shown below.  Impressive!

M5.0 – 25km NNE of Shawville, Canada

There was a moderate, Magnitude 5.0, earthquake in southern Ontario, Canada this morning.  It registered as a small but nicely formed signal on my seismograph in northeastern Ohio, showing the P, S, and surface arrivals.  The orientation of my seismograph makes it less sensitive to earthquakes north and south of my location than it is to earthquakes east or west of us.  By my calculation this earthquake was about 456 miles northeast of my location.

USGS Event page is here: http://earthquake.usgs.gov/earthquakes/eventpage/usb000gxna#summary

Postscript: 

The USGS reduced the magnitude estimate to 4.4 after this post was written.

New Page — Clear Sky Charts

With the transit of Venus rapidly approaching above cloudy skies I was very curious to see if the forecast was for clearing skies at the last minute.  My go-to website for that information is The Clear Sky Chart Homepage.   My experience has been that it is pretty accurate.  Then I realized that the authors permit embedding the chart on non-commercial websites like mine so I added a new page with charts for two locations on either side of my location in Millersburg, Stillwell and Wilmot, all in Ohio.  Find the new page in the sidebar at the right hand side of the page labeled “Clear Sky Chart“

“Live” Seismograph Display

I have wanted to share the helicorder display from my seismograph for a long time.  Finally this week I think I have a method to do it.  I put it on its own page here.   The image will be updated every 5 minutes but you will need to manually refresh the page to get the most recent display.

Of course, this will depend on my having internet access…it went down for a couple of hours while I was writing this post.

Magnitude 7.0 – NORTHERN PERU

A major magnitude 7.0 earthquake occurred in Northern Peru this afternoon.  At a depth of 145 km it shows minimal surface phases and because it is south of my location in northeastern Ohio the transverse S-phase arrival is strong.

The travel time information from the USGS Travel Time calculator is shown below:

  DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
  2011/08/24 17:46:11   7.64S  74.51W 145.1 7.0      US: NORTHERN PERU
   Expected 1s period body wave amplitude     [  3.06E+00 µm]  [  1.92E+01 µm/s]

 delta   azimuth (degrees clockwise from north)
 (deg)      eq-to-station     station-to-eq
 48.44          352.5             170.2

                 travel   arrival time
    #  code      time(s)  dy hr mn sec
    1  P          507.44   0 17 54 38
    2  pP         540.38   0 17 55 11
    3  sP         556.85   0 17 55 27
    4  PcP        591.27   0 17 56  2
    5  PP         621.51   0 17 56 32
    6  PP         624.66   0 17 56 35
    7  ScP        812.11   0 17 59 43
    8  PcS        827.54   0 17 59 58
    9  S          917.67   0 18  1 28
   10  sS         975.47   0 18  2 26
   11  PKiKP     1000.78   0 18  2 51
   12  pPKiKP    1039.54   0 18  3 30
   13  sPKiKP    1054.61   0 18  3 45
   14  ScS       1084.90   0 18  4 15
   15  SS        1130.91   0 18  5  1
   16  SS        1142.47   0 18  5 13
   17  SKiKP     1199.19   0 18  6 10
   18  PKKPdf    1871.17   0 18 17 22
   19  SKKPdf    2069.62   0 18 20 40
   20  PKKSdf    2084.70   0 18 20 55
   21  SKKSdf    2283.03   0 18 24 14
   22  P'P'df    2374.35   0 18 25 45
   23  P'P'ab    2425.45   0 18 26 36
   24  S'S'df    3215.45   0 18 39 46
   25  LQ        1229.43   0 18  6 40
   26  LR        1364.50   0 18  8 55