New Page — Lehman Seismograph Construction Notes

I have added a new page under Seismology/Lehman Seismograph section in response to occasional questions about the construction details of my Lehman seismograph.  I have included some rough dimensions and general layout but in my experience following them exactly is not necessary.  A quick scan of the web based collection of Lehman projects shows an amazing array of designs which apparently work.  The Lehman concept is very forgiving, at least within broad constraints.

I have tried to answer questions I have already received and will add additional material if new questions arise.

M5.0 – 25km NNE of Shawville, Canada

ontario_5_17may2013

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.

Magnitude 4.0 – YOUNGSTOWN-WARREN URBAN AREA, OHIO

A Magnitude 4.0 earthquake was reported this afternoon at 20:04:58 UTC in northeastern Ohio.  This is in the same area as a sequence of earthquakes thought to be associated with injection wells used to dispose of oil drilling waste fluids.  The injection wells operations were suspended yesterday by the state of Ohio and the operator of the well.

Even though my seismograph in Millersburg, OH  is not well suited to picking up local earthquakes and the display has been quite noisy the last few days, with a small amount of processing I did pick up a signal that appears to be caused by the earthquake in question.

The USGS arrival time information is shown:

DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
2011/12/31 20:04:58  41.16N  80.73W   2.2 4.0      us: YOUNGSTOWN-WARREN AREA,

delta   azimuth (degrees clockwise from north)
(deg)      eq-to-station     station-to-eq
1.06          236.2              55.4

travel   arrival time
#  code      time(s)  dy hr mn sec
1  Pg          20.39   0 20  5 18
2  sPg         20.92   0 20  5 18
3  Pb          21.09   0 20  5 19
4  pPb         21.44   0 20  5 19
5  sPb         21.83   0 20  5 19
6  Pn          21.88   0 20  5 19
7  pPn         22.41   0 20  5 20
8  sPn         22.74   0 20  5 20
9  Sg          35.19   0 20  5 33
10  Sb          36.46   0 20  5 34
11  sSb         37.05   0 20  5 35
12  Sn          38.13   0 20  5 36
13  sSn         39.00   0 20  5 37
14  PcP        510.96   0 20 13 28
15  ScP        722.84   0 20 17  0
16  PcS        723.12   0 20 17  1
17  ScS        935.02   0 20 20 33
18  PKiKP      994.23   0 20 21 32
19  pPKiKP     994.99   0 20 21 32
20  sPKiKP     995.27   0 20 21 33
21  SKiKP     1206.10   0 20 25  4
22  PKKPdf    1917.27   0 20 36 55
23  SKKPdf    2129.14   0 20 40 27
24  PKKSdf    2129.42   0 20 40 27
25  SKKSdf    2341.29   0 20 43 59
26  P'P'df    2428.55   0 20 45 26
27  S'S'df    3276.86   0 20 59 34

Postscript:

Several people have asked me about the triggering of earthquakes by hydraulic fracturing and waste injection wells.  The USGS has a FAQ page on the subject.

“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