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