Magnitude 7.0 – SANTIAGO DEL ESTERO, ARGENTINA

A Major, magnitude 7.0 earthquake struck Argentina this morning at 09:56:59 UTC.  Given its depth at 583 km little damage is expected from it.  This earthquake occurred on the subduction zone that runs along the west coast of South America.  The major fault breaks the surface along the coast with the sub-ocean plate being subducted under the South American continent.  An east-west cross-section would show the earthquake focii becoming deeper the further east they occur.  This fault is responsible for the formation of the Andes mountain range and numerous volcanoes along the western side of South America.

The seismogram trace recorded in Northeastern Ohio shows distinct P and S phase arrivals but no surface phase because of the depth of the focus.  The smaller phase just to the right of the big S phase return is the ScS phase, the reflection of the S phase off the earth’s core.  These are common on South American earthquakes at my location (as described here).

Results from the USGS Arrival Time calculator are shown below:

DATE-(UTC)-TIME    LAT    LON     DEPTH MAG   Q   COMMENTS
2011/01/01 09:56:59  26.76S  63.10W 583.6 7.0      US: SANTIAGO DEL ESTERO, ARG
Expected 1s period body wave amplitude     [  5.01E+00 µm]  [  3.15E+01 µm/s]
  

delta   azimuth (degrees clockwise from north)
(deg)      eq-to-station     station-to-eq
69.21          344.8             162.1

travel   arrival time
#  code      time(s)  dy hr mn sec   
 1  P          609.17   0 10  7  8
 2  PcP        627.89   0 10  7 26
 3  pP         727.20   0 10  9  6
 4  PP         772.35   0 10  9 51
 5  sP         788.16   0 10 10  7
 6  PKiKP      977.40   0 10 13 16
 7  S         1110.06   0 10 15 29
 8  pPKiKP    1113.37   0 10 15 32
 9  SKiKP     1135.72   0 10 15 54
10  SPn       1139.55   0 10 15 58
11  SKSac     1152.43   0 10 16 11
12  SKKSac    1152.61   0 10 16 11
13  ScS       1154.13   0 10 16 13
14  sPKiKP    1169.68   0 10 16 28
15  sS        1321.55   0 10 19  0
16  pSKSac    1323.56   0 10 19  2
17  sSKSac    1387.01   0 10 20  6
18  SS        1393.13   0 10 20 12
19  PKKPdf    1795.46   0 10 26 54
20  SKKPdf    1953.88   0 10 29 32
21  PKKSdf    2010.20   0 10 30 29
22  SKKSdf    2168.42   0 10 33  7
23  P'P'bc    2291.59   0 10 35 10
24  P'P'df    2292.84   0 10 35 11
25  P'P'ab    2293.43   0 10 35 12
26  S'S'df    3098.13   0 10 48 37
27  LQ        1756.72   0 10 26 15
28  LR        1949.72   0 10 29 28