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

Two Oklahoma Earthquakes

I was busy yesterday and had missed the earthquake activity in Oklahoma.  The Magnitude 5.6 event early this morning (UTC) shown in the bottom of the display,  was large enough to trigger a notification to me from the USGS but the others were below the threshold that I had set.  When I looked this morning I had also picked up the Mag 4.7 at 7:12:45 UTC shown toward the top of the display.  The display shows the relative difference in the size of the waveform for two earthquakes at the same distance but with a 0.9 difference in magnitude.  The larger earthquake released 22.4 times as much energy as the smaller one and should be about 7.9 times bigger on the seismograph.

Magnitude 5.6 – OKLAHOMA

A moderate Magnitude 5.6 earthquake struck Oklahoma at 3:53:10 UTC on Sunday November 5, 2011.  The display shows the waveform received in northeastern Ohio.  The waveform structure for earthquakes this close is complicated and since we don’t often see them I haven’t spent a lot of time trying to decipher it.  The simple body and surface waves are not even listed in the USGS arrival time list shown below:

 DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
  2011/11/06 03:53:10  35.54N  96.75W   5.0 5.6      US: OKLAHOMA
   Expected 1s period body wave amplitude     [  3.92E-02 µm]  [  2.47E-01 µm/s]

 delta   azimuth (degrees clockwise from north)
 (deg)      eq-to-station     station-to-eq
 12.74           62.4             251.6

                 travel   arrival time
    #  code      time(s)  dy hr mn sec
    1  Pn         181.74   0  3 56 11
    2  pPn        182.95   0  3 56 12
    3  sPn        183.70   0  3 56 13
    4  PnPn       189.55   0  3 56 19
    5  PbPb       223.00   0  3 56 52
    6  PgPg       244.02   0  3 57 14
    7  Sn         325.16   0  3 58 35
    8  sSn        327.17   0  3 58 37
    9  SnSn       338.39   0  3 58 48
   10  SbSb       386.32   0  3 59 36
   11  SgSg       421.22   0  4  0 11
   12  PcP        518.14   0  4  1 48
   13  ScP        731.92   0  4  5 21
   14  PcS        732.55   0  4  5 22
   15  ScS        948.32   0  4  8 58
   16  PKiKP      995.55   0  4  9 45
   17  pPKiKP     997.27   0  4  9 47
   18  sPKiKP     997.90   0  4  9 47
   19  SKiKP     1207.17   0  4 13 17
   20  PKKPdf    1914.90   0  4 25  4
   21  SKKPdf    2126.52   0  4 28 36
   22  PKKSdf    2127.15   0  4 28 37
   23  SKKSdf    2338.76   0  4 32  8
   24  P'P'df    2425.57   0  4 33 35
   25  P'P'ab    2599.91   0  4 36 29
   26  S'S'df    3274.10   0  4 47 44

Magnitude 7.2 – EASTERN TURKEY

The major 7.2 magnitude earthquake in Eastern Turkey registered on my seismograph in northeastern Ohio this morning showing several very distinct phase arrivals.

 

“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

Magnitude 5.9 – VIRGINIA

A Magnitude 5.9 earthquake occurred a little before 2:00 pm EDT in Virginia today.  A number of people felt it here in northeast Ohio.

The earthquake magnitude and proximity of the earthquake to my station caused the signal to go off scale.  The AmaSeis software doesn’t scale well on the travel time display so the best I can do is post the extracted signal.

This is an unusual earthquake for the eastern United States although even larger earthquakes have occurred in the region.  Earthquakes in the eastern U.S. are thought to occur on remnant faults left over from the breakup of the super-continents hundreds of millions of years ago.  These can be visualized by looking at the map I have here.  The location depth calculation for this earthquake was poorly constrained but was apparently very shallow, being perhaps less than a kilometer, also unusual.

For what it is worth, here are the travel times for the various phases given by the USGS calculator for my location:

DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
2011/08/23 17:51:03  37.97N  77.97W   1.0 5.9      us: VIRGINIA
Expected 1s period body wave amplitude     [  1.11E+00 µm]  [  6.98E+00 µm/s]

delta   azimuth (degrees clockwise from north)
(deg)      eq-to-station     station-to-eq
3.99          311.6             129.1

travel   arrival time
#  code      time(s)  dy hr mn sec
1  Pn          62.33   0 17 52  5
2  pPn         62.57   0 17 52  5
3  sPn         62.72   0 17 52  5
4  PnPn        69.86   0 17 52 12
5  Pb          71.16   0 17 52 14
6  pPb         71.32   0 17 52 14
7  sPb         71.50   0 17 52 14
8  PbPb        74.30   0 17 52 17
9  Pg          76.56   0 17 52 19
10  pPg         76.57   0 17 52 19
11  PgPg        76.57   0 17 52 19
12  PgPg        76.70   0 17 52 19
13  sPg         76.80   0 17 52 19
14  Sn         110.85   0 17 52 53
15  sSn        111.25   0 17 52 54
16  SnSn       123.13   0 17 53  6
17  Sb         123.24   0 17 53  6
18  sSb        123.51   0 17 53  6
19  SbSb       128.57   0 17 53 11
20  Sg         132.15   0 17 53 15
21  sSg        132.17   0 17 53 15
22  SgSg       132.18   0 17 53 15
23  PcP        511.88   0 17 59 34
24  ScP        724.12   0 18  3  7
25  PcS        724.25   0 18  3  7
26  ScS        936.69   0 18  6 39
27  PKiKP      994.60   0 18  7 37
28  pPKiKP     994.95   0 18  7 37
29  sPKiKP     995.07   0 18  7 38
30  SKiKP     1206.63   0 18 11  9
31  PKKPdf    1917.31   0 18 23  0
32  SKKPdf    2129.34   0 18 26 32
33  PKKSdf    2129.46   0 18 26 32
34  SKKSdf    2341.49   0 18 30  4
35  P'P'df    2428.53   0 18 31 31
36  S'S'df    3277.04   0 18 45 40

Two Colorado Earthquakes

Raw Helicorder Display showing both August 23 earthquakes

Last evening before I went to bed I noticed a small earthquake on my seismograph here in northeastern Ohio. The prominence of the surface phases indicated that it was some distance away but still its appearance suggested that it would still be the Americas. I estimated the time of occurrence and checked my email but found nothing reported there so I checked the USGS Earthquake Hazards site. The 4.6 Magnitude earthquake in Colorado was not in the set of magnitude and location parameters that I have defined to trigger notifications but it generated a very clean signal here in Ohio.

Magnitude 4.6 Colorado - August 22, 2011

This morning when I got up I did my customary quick check of the overnight emails on my iPod finding a Magnitude 5.3 earthquake in the same area. It also showed a very clean signal on my seismograph with all of the major phases showing quite well…a small P phase, the S, and both the Love and Rayleigh surface phases.

Magnitude 5.3 Colorado - August 23, 2011

Magnitude 7.2 – FOX ISLANDS, ALEUTIAN ISLANDS, ALASKA

A major 7.2 magnitude earthquake occurred at 2011 June 24 03:09:40 UTC  near the Fox Islands in the Aleutian Island chain in southwestern Alaska.  No tsunami alerts were issued.

Unknown Spectral Feature in Aircraft Overflight Spectrum – Resolved

Unknown Spectral Feature - Chinook Helicopter

Almost a year and a half ago, I put out a request for help in understanding a shallow bowl-shaped feature in the spectrogram of the sound of aircraft flying overhead. My older son had already suggested that it was a multi-path interference pattern and his suggestion was supported a couple of months later by commenter Alberto Armani.

Finally last week, I took time to sit down and think clearly about how that would work. As it turns out, the model is very simple and seems to explain the shallow bowl-shaped feature in the the spectrogram. I need to make a couple of sketches of the geometry before I can put up a page on this subject but I’ll try to get it done in the next week or so.

Postscript:

I have added a page describing the ground reflection interference model here.