GLOBAL SEISMICITY ZONES

The Global Map has been divided into 16 zones according to each area's characteristic location. The Global Map only shows Big Earthquakes (Magnitud > 8.0). Taking into account seismicity > 7.0 (major and Big Earthquakes) for the period 1973 01 01 thru 2006 12 31, zones number 9 (Sumatra 20.5%) and number 6 (Tonga 18%) are the most seismic zones in the world. Next come zones number 5 (Japan and Philipines 10.3 %) , number 1 (Nazca Plate Subduction Zone 9.5 %) and number 4 (Alaska and Kamtchaka 8.2%). Zone number 10 accounts for 5.6%, and zones number 2, number 3, number 8, number 11 and number 12 account for around 3 % of total global seismicity.

Taking into account a longer period of time, 1940 thru 2006, some positions change, but overall, the pattern of seismicity holds. Extrangely enough, this same pattern of seismicity that you see in the Global Map for Big Earthquakes in 30 or 60 years, you see for a period of 30 to 60 days if you take into account earthquakes of magnitude > 4.0 or > 5.0.

The Global Map shows four Big Earthquakes of magnitude = or > 8.4. These are Sumatra (9.0), Antartic Plate (8.8), Alaska (8.5) and Southern Peru (8.4).

NAZCA PLATE SUBDUCTION ZONE SEISMICITY

Seismicity at the NPSZ as, detailed in this map, is quite staightforward if you look at it from right to left. The red coloured circles represent Extra Deep Earthquakes (EDE's) with depths ranging from 500Kmsto 670 Kms. These EDE's occurr at the bottom limit of the subducting Nazca plate, where at, melting of the materials take place, therefore no more earthquakes beyond this limit. EDE's range from the Equator (0º) south to the -30 º Latitude. There are no EDE's south from this latitude or north from the Equator. Also, EDE's are located below the flat lands East from the Andes Mountains.

The blue coloured circles represent Very Deep Earthquakes (VDE's) with depths ranging from 175 Kms to 330 Kms which take place mostly under the eastern rise ofthe Andes Mountains. Only a few earthquakes occurr at depths in between 350 and 450 Kms (the transition zone of earth's inner layers) and one of them is present close to the latitude-20º, longitude - 65º intersection (this 6.1 Mw magnitude earthquake took place on 2004 03 27 and is coloured purple).

The double blue line joining the orange coloured circles on the eastern limit of the Andes Mountains represent Surface Level Out Of Place Seisms (SLOOPS or CRE's for Crust Response Earthquakes), earthquakes which take place at upper crust levels and which do not belong to the subducting plate process but to the longitudinal shortening of the continent, caused instead by the Mid Atlantic Ridge weternly push. This process of shortening creates the rising of the Andes Mountains.

Under the western rise of the Andes Mountains, the green coloured circles represent Medium Depths Eathquakes (MDE's or IDE's) at the intermediate depths of 75 Kms to 175 Kms. MDE's at depths 90-110 Kms follow the line under the AndesMountains highest's peaks and this depths is the usual source to magma in the volcanic processes.

Yellow circles near the coastal line represent earthquakes at depths in between 40 and 75 Kms. Some of these earthquakes are situated below the subducting plate and areOut of Place Seisms (OOPS's or MRE's for Mantle Reponse Earthquakes)

Orange Circles near the Coast Line represent earthquakes at depths of 0 to 39 Kms. Most of the earthquakes at the subduction zone take place at these depths and certainly the most violent ones too because of their closeness to the surface.