SEISMIC SYSTEMS IN BAJA CALIFORNIA (NW MEXICO)
After the Sierra El Mayor Earthquake in Baja California (Mexico) dated April 4, 2010, M7.2, we revealed SS Baja California, responsible for its preparation, and SS Gulf of California (Mexico), responsible for strong earthquakes in the Northwest of Mexico. Was estimated the influence of Sierra El Mayor Earthquake on the seismic situation in California (USA). /April 09, 2010/
EFFECT OF Sierra El Mayor Earthquake AT SEISMIC SITUATION IN CALIFORNIA.
Since the seismic situation in South California within the next few years can be very dangerous, we investigated the influence of Sierra El Mayor Earthquake ☼ on the scenario of the development of seismicity and the forecasts of earthquakes in South California from M>6.6, given in Bulletin 002. For this purpose we reviewed combined SS Baja California, San Jacinto, San Bernardino. Preliminary analysis showed that the growth of entropy in an unstable state (M>6.6) convert the faults from South to North: at first Laguna Salada Fault, then Imperial Fault, then South and North segments of San Jacinto Fault. It can be concluded that after earthquake on April 4 were discharged the Laguna Salada Fault and Imperial, and stress concentration moved to the north of system San Jacinto. Was somewhat discharged situation in SS San Bernardino, on the southern segment of San Andreas Fault. Summing up it is possible to say that after Sierra El Mayor Earthquake the probability of the first scenario of the preparation of catastrophic earthquake on the San Andreas Fault grew in comparison with the second (see Bulletin 002).
SS Baja California, FORECAST, Ms≥6.6. After Sierra El Mayor Earthquake ☼ we revealed seismic system Baja California (see Fig.1), responsible for its preparation. For the development of boundaries this system we studied the seismic zone, which is stretched to the southeast into the Gulf of California. Seismicity is here caused by interaction of Pacific Ocean plate with North American plate. The boundary of plates consists of a series right-lateral transform faults of North Western orientation, which are stretched from the south of Gulf California to Salton Sea Trough in South California, where terminate San Andreas Fault. These faults are disconnected by the spreading centers with the high heat fluxes.
Revealed SS Baja California on the north partially overlaps previously revealed SS San Jacinto (monitoring since 1996), and in the south it is isolated from SS Gulf of California by spreading Basin Wagner -Delphin (see Fig.1).
RETROSPECTIVE. In SS Baja California we made a retrospective forecast of Sierra El Mayor Earthquake ☼. The trajectory of the preparation of this strong earthquake started after the earthquake on October 17, 1979 and toward the end 2009 it was located below attractor. Earthquake-indicator dated December 30, 2009, M=5.8 raised track, it fell into the zone close to the unstable region for the Imperial Fault (see Fig.2a):
Ê=1.44W - 9.84 at W>16.5 0 (1)
Earthquake occurred after three months, on March 4, 50 km is southwestern than the Imperial Fault, on the parallel Laguna Salada Fault. On the Laguna Salada Fault in the system occurred historical earthquake on February 23, 1892, M=6.9; however, its trajectory to us was unknown. For this reason the retrospective forecast of the place of earthquake - Fault Imperial or Laguna Salada. The distinctive feature of the tracks preparation of strong earthquakes in SS Baja California is that they have relatively low values of cumulative energy with the high values of entropy. Until April 4 the probability of earthquake from Ms≥6.6 in the system was high Ð=50.90% (PW=83.74% PK=60.77%) (see Fig.2b). Thus, a strong earthquake, preparation of which lasted 29 years, it was possible to expect since the beginning of 2010 on the Imperial Fault or Laguna Salada Fault. Now in the system it is not dangerous, earthquakes from M≥6.6 are not expected.
SS Gulf of California, FORECAST, Ms≥6.6. System was revealed on the basis of earthquake catalog since 1954. It is stretched on the Gulf of California by 900 km and has a width of 300 km (see Fig.1). The strongest earthquakes have magnitudes 6.9-7.0. Is outlined migration in time of earthquakes with M≥6.6 from southeast to northwest. Last strong earthquake occurred on August 3, 2009, M=6.9. The probability in the system before this earthquake was equal Ð=41% (PW=81% PK=51%). Now in the system it is not dangerous, earthquakes from M≥6.6 are not expected.
Fig.2à. Fragment of track diagram for SS Baja California. The trajectory of preparation of the moderate earthquake (heavy red line) from M≥6.6 after the jump of December 30, 2009, by April 2010 approached the zone of instability for Imperial Fault.
Fig.1. Southern California (USA), NW Mexico. Controlled areas of seismic systems: San Jacinto, Baja California and California Gulf. Showing earthquake epicenters of August 3 2009, on April 4, 2010 and foreshock December 30, 2009.
Fig.2b. Dynamics of an increase in the probability of strong earthquake from M≥6.6 in SS Baja California before the earthquake on April 4, 2010.
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☼ Sierra El Mayor Earthquake in Baja California, NW Mexico
2010.04.04 22:40:41 32.13N 115.30W H=10 km Ì=7.2
Intensity, source, aftershocks.