Chilean fault dynamics similar to California's great San Andreas.
A monstrous earthquake—registering 8.2 on the Richter scale struck just off the Chilean west coast Tuesday night and continues to followed by unceasing and powerful aftershocks, in the 5 to 6 magnitude range, including one which measured 6.7.
Damage reports were instantaneous; roads, highways and bridges were affected. Homes, buildings and offices experienced damage with a confirmed death toll of at least six. Fires broke out and evacuations were ordered. The initial quake struck 59 miles northwest of Iquique, Chile. According to researchers, the earthquake was violent enough to move the Chilean city of Concepcion at least 10 feet westward and Santiago about 11 inches to the west-southwest.
Massive earthquakes have been relatively common to this region, the strongest quake ever recorded in modern history occurred in Chile in 1960, measuring 9.5.
Tuesday night's 8.2 quake occurred at a relatively shallow depth of 12.5 miles and strongly shook an area of hundreds of square miles. Shock waves were felt as far away as both Peru and Bolivia. Tsunami advisories and warnings were almost instantaneously issued for a broad area of the Pacific. Six foot waves were reported along the Chilean coast within a short time of the main shock. The broad scale warnings were downgraded, but continue to be in effect for Hawaii where potentially damaging waves were expected to begin arriving there this Wednesday morning.
This region of the world lies within a very unstable boundary between tectonic plates, which are a constant state of friction as they grind against each other. According to the U.S. Geological Survey:
“The April 1, 2014 M8.2 earthquake in northern Chile occurred as the result of thrust faulting at shallow depths near the Chilean coast. The location and mechanism of the earthquake are consistent with slip on the primary plate boundary interface, or megathrust, between the Nazca and South America plates. At the latitude of the earthquake, the Nazca plate subducts eastward beneath the South America plate at a rate of 65 mm/yr. Subduction along the Peru-Chile Trench to the west of Chile has led to uplift of the Andes mountain range and has produced some of the largest earthquakes in the world, including the 2010 M 8.8 Maule earthquake in central Chile, and the largest earthquake on record, the 1960 M 9.5 earthquake in southern Chile.”
USGS also points out that activity in this area has been unusually high during the past few months. Strain patterns in the earth's crust which trigger earthquakes are very complex, but at least one prominent scientist states more is likely to come: "This magnitude 8.2 is not the large earthquake that we were expecting in this area," said Mark Simons, a geophysicist at Caltech in Pasadena, California. "We're expecting a potentially even larger earthquake." This hypothesis is based on recent and not-so-recent activity, which includes a number of major quakes in the region going back decades and, once again, the world's strongest quake in 1960, measuring 9.5.
California's great San Andreas fault, long overdue for a major event near Los Angeles, is very similar in character to fault zones along and off the Chilean coast. The term “strike-slip” is used by geologists to describe the lateral (sideways shift/displacement) which was and has been a factor in Chilean quakes. Great earthquakes in California, including the San Francisco earthquake of 1906, the southern California earthquake of 1857 which affected Los Angeles, and the Loma Prieta quake back in 1989 involved strike-slip or lateral motion. Instantaneous displacements of up to 30 feet can occur with major quakes of this variety.