Magnitude 8.9 – NEAR THE EAST COAST OF HONSHU, JAPAN

A magnitude 8.9 (Great) earthquake struck off the east coast of Japan at 05:46:23 UTC on March 11, 2011.  This earthquake  generated a large tsunami which is propagating across the Pacific Ocean as I am writing this.  NPR reported a 30 foot tsunami in Japan.  In the 6 hours following the main shock I have received over 30 reports of aftershocks with magnitudes greater than 5.5 .  The strongest aftershock was a magnitude 7.1 tremor at 06:25:51 UTC.  This was the same magnitude as the devastating earthquake in Haiti last year.  The main shock of magnitude 8.9 released 500 times more energy than the magnitude 7.1 aftershock.  The screenshot above shows the raw helicorder display early this morning in northeastern Ohio.

Here is a screenshot of the extracted and filtered signal from my seismometer:

The arrival time information for my location from the USGS arrival time calculator are shown below:

DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
2011/03/11 05:46:23  38.32N 142.37E  24.4 8.9      US: NEAR EAST COAST OF HONSH
Expected 20s period surface wave amplitude [  4.40E+03 µm]  [  1.38E+03 µm/s]
Expected 1s period body wave amplitude     [  5.42E+01 µm]  [  3.40E+02 µm/s]

delta   azimuth (degrees clockwise from north)
(deg)      eq-to-station     station-to-eq
91.68           32.1             326.7

travel   arrival time
#  code      time(s)  dy hr mn sec
1  P          785.14   0  5 59 28
2  PcP        785.84   0  5 59 28
3  pP         793.14   0  5 59 36
4  sP         796.19   0  5 59 39
5  PP        1003.52   0  6  3  6
6  PKiKP     1076.17   0  6  4 19
7  pPKiKP    1084.38   0  6  4 27
8  sPKiKP    1087.39   0  6  4 30
9  SKiKP     1289.00   0  6  7 51
10  SKSac     1415.68   0  6  9 58
11  pSKSac    1426.62   0  6 10  9
12  sSKSac    1429.71   0  6 10 12
13  SKKSac    1431.19   0  6 10 14
14  S         1444.18   0  6 10 27
15  ScS       1446.43   0  6 10 29
16  pS        1454.65   0  6 10 37
17  sS        1457.87   0  6 10 40
18  SP        1513.76   0  6 11 36
19  SPn       1514.53   0  6 11 37
20  PS        1517.13   0  6 11 40
21  PnS       1517.95   0  6 11 40
22  SS        1812.66   0  6 16 35
23  PKKPdf    1822.09   0  6 16 45
24  PKKPbc    1823.27   0  6 16 46
25  SKKPdf    2035.08   0  6 20 18
26  PKKSdf    2038.09   0  6 20 21
27  SKKPbc    2040.68   0  6 20 23
28  PKKSbc    2043.70   0  6 20 26
29  SKKSdf    2250.87   0  6 23 53
30  SKKSac    2259.89   0  6 24  2
31  P'P'df    2315.18   0  6 24 58
32  S'S'df    3177.82   0  6 39 20
33  S'S'ac    3178.50   0  6 39 21
34  LQ        2326.87   0  6 25  9
35  LR        2582.50   0  6 29 25
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