STRONG EARTHQUAKES, BADLY PREDICTED IN SS

    In the zones of collision and subduction of plates local faulting tension areas with the normal focal mechanisms of strong earthquakes can be formed (type D). The first time this encountered, when I was revealed SS in Southern California. It is not much to the happiness of such zones, but last devastating earthquake in Italy showed that the method of seismic entropy must be enlarged for control and forecast of strong earthquakes in these zones. In SS strong earthquakes, timed to such local zones, as a rule, badly are predicted or in no way have a preparation. I here will not stop above the physical explanation, why this is happening.Such zones of strong earthquakes in more than 40 revealed SS were only three: in SS Southern California, SS Central Italy and on the frontal boundary SS Central Kuril. Let us describe earthquakes with the normal focal mechanisms in these systems.

SS Central Italy. Cascade of earthquakes in central Italy on the Umbria-Marche region in September-October 1997 (see. Fig.2)

 

 1997.09.26     09:40:26  43.08N  12.81E  H=10 km,  M=6.40

 

   The epicentres of two basic quakes on September 26, 1997 were arranged near Colfiorito. Earthquakes had normal mechanism, with the slip plane, which is dipping in the SW direction. Taking into account total energy the cascade of earthquakes, this event we examined as one strong earthquake from Ms=6.2. In the system central Italy this earthquake badly was predicted, it did not have the necessary value of cumulative energy and entropy.

    In central Italy the dominant activation falls on the heterogeneities zones of Ankona-Anzio, Rocca-Ortona, Vesuvius-Termoli and etc., with NE left-lateral strick-slip componentс. The distinctive characteristics of soutern parts of these zones are active volcanism, differential variations of crust depth and heat flow anomalies. The fault-plane in central Italy only normal faulting mechanisms that are the NE-dipping nodal plane. Extention in this zone occurs by steep normal faulting in the upper 10-15 km. of the crust. The fault-plane solution of earthquake occurred close to the Anzio-Ancona line show dominantly normal faulting with NE left-lateral strick-slip component. Major structural trends change from a NW-SE to E-W trend in this area.

 

SS San Jacinto, Southern California.

   On fig.3 is shown the dynamics of accumulation and discharging of stresses in SS San Jacinto in Southern California and the epicentre of earthquake   

1906.04.19  00:30   32.90N   115.50W  Ms=6.2   Imperial Valley,

which, also as in central Italy, adds to the class of the difficultly forecasted earthquakes.

 

    Of 15 strong earthquakes in this system only earthquake Imperial Valley did not have a preparation. The seismic cycle of the preparation of this earthquake had to start after the Christmas Day earthquake of 1899.12.25, M6.4, but necessary increase in the entropy it was not observed. As can be seen from Fig.3, the Salton Trough is the local zone of spreading (tension) between two right strick-slip transform faults San Andreas and Imperial. The earthquake of 1906 was timed to this tension area and  had a normal faulting.

Fig. 2

Fig. 1

Fig. 3

SS Central Italy, Мs≥5.8.

   On the forecast of the strong earthquake in central Italy  

 

   2009.04.06     01:32:43  42.40N  13.32E  H=10 km,  Ms=6.2  (L'Aquila)

 

  On the basis of the method of seismic entropy this earthquake in SS Central Italy was not forecast (see Bulletin 001), since it did not have preparation necessary for this class of strong earthquakes. I will try to elucidate, why? This earthquake by the focal mechanism according to our classification adds to rare and it is difficult forecast. You in more detail look new page on the site of the Areas of application of the method of seismic entropy.  

   The earthquake L'Aquila had clearly expressed normal faulting on a NW-SE orientation (see Fig.1), and for this reason it did not have a sufficient preparation within the framework of system Central Italy. Track is the preparation of L'Aquila earthquake started after strong earthquake on October 31, 2002 WNW of Foggia (San Giuliano di Puglia) and at the moment of earthquake on April 6, 2009 had the small values of cumulative energy and entropy.

   Of 30 strong earthquakes in seismic systems and subsystems of Italy only 2 we add to this class. To this type of earthquakes in Central Italy relates the earthquake of 1997, which was also badly predicted by the method of seismic entropy.

   Let us examine in more detail all earthquakes of such type in those revealed by us SS.

Fig. 4

SS Central Kuril.

   In central Kuril in two monthly interval inside and out of the island arc occurred two strong earthquakes (see Fig.4)

 

2006.11.15 11:14:16  46.68N  153.22W  H=28 km  M=8.3       

2007.01.13 04:23:20  46.27N  154.46W  H=10 km  M=8.2

 

that differed by focal mechanisms of source. The first one had a thrust mechanism (Type A), the second of normal (Type D). If the first earthquake was predicted well in SS, then the second strong earthquake, completely obviously, not as it could have preparation for so short time interval after the first within the framework of system.

   In the case of Kuril a question it was decided very simply. Taking into account mechanism and place of epicenter of the second strong earthquake (violet region on Fig.4) and the spatial distribution of the epicentres of indicator earthquakes (yellow region on Fig.4), the second earthquake were brought out beyond the framework SS Central Kuril. The physical interpretation of the validity of this selection on the basis of the deformation of plates in the subduction zones I do not here lead.

    I will note that the forecasts of strong earthquakes those given in Bulletin 001 for the Central Kuril, controls seismic systems and subsystems in the yellow zone (in the Sea of Okhotsk plate). Specifically, for this reason our forecast did not concern earthquake dated January 15, 2009, M7.6 (see Fig.4) and therefore I to it did not react.

 

Seismic chess: the analysis of the seismic parties, played by Nature

   Being expressed in the language of seismic chess: some seismic parties, played by Nature in Central Italy, Southern California and in Kuril are unique and require thin analysis. In the case of Kuril the solution was found, while in the very similar parties in Southern California and in Central Italy one should be dismantled for their forecast in the future.

   Akopian S.Ts. 

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