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
