November 1, 2012 – Global Earthquakes by Month for Calendar Year 2012: The graphs above reflect all global earthquakes greater than or equal to (>=) 6.0 magnitude, from January 1, 1973 through October 31, 2012.
The forecast bar is a summation of the 40 year period, from 1973 to 2012 divided by 40. The actual bar is global earthquakes that occurred that month.
The large height of the April 2012 actual bar reflects the double Indonesian (8.6 and 8.2) quakes that month. This was highly unusual and saw two “monster” quakes within two hours and four minutes of each other. The 8.6 event occurred at 8:39AM (Apr. 11th), while the 8.2 event occurred at 10:43AM. The first quake was at 2 degree North Latitude and 93 degrees East Longitude. The second quake shifted south by one degree and east by one degree.
The following is from the USGS Website: “The April 11, 2012, M8.6 and M8.2 earthquakes off the west coast of northern Sumatra, Indonesia, occurred as a result of strike-slip faulting within the oceanic lithosphere of the Indo-Australia plate. The quakes were located respectively 100 km and 200 km to the southwest of the major subduction zone that defines the plate boundary between the India/Australia and Sunda plate’s offshore Sumatra. At this location, the India/Australia plates move north-northeast with respect to the Sunda plate at a velocity of approximately 52 mm/yr.”
“Large strike-slip earthquakes are not unprecedented in the diffuse boundary region separating the India and Australia plates, southwest of the Sumatra subduction zone. Since the massive M 9.1 earthquake that ruptured a 1300 km long segment of the Sumatran megathrust plate boundary in December of 2004, three earlier large strike-slip events had occurred within 50 km of the first large April 11, 2012 event. These earthquakes occurred on April 19 2006 (Mw6.2), October 4 2007 (Mw6.2) and January 10, 2012 (Mw7.2). The focal-mechanisms of the three earlier earthquakes and the two great earthquakes of April 11, 2012, are consistent in implying that each earthquake could have occurred as the result of left-lateral slip on a north-northeast striking fault or right-lateral slip on a west-northwest striking fault. The two different orientations of strike-slip faulting are both possible under the same tectonic stress field; perpendicular strike-slip faults that are both compatible with the same stress field are called “conjugate faults.” Possibly faults of both orientation have been involved in the recent earthquake activity.”
In other words, the December 26 2004 mega-quake and tsunami has seen five major aftershocks over the last eight years. One on April 19 2006 (6.2), one on October 4 2007 (6.2), two on April 11 2012 (8.6 and 8.2) and one on January 10 2012 (7.2). This pattern is worrisome in that the magnitude of the aftershocks is significantly increasing and the time between major events is shortening.
The Master of Disaster