HR: 16:20h
AN: IN24A-01    [Abstracts]
TI: The Depth of 60-80 km as the Boundary of External Factor Influence on the Earth's Lithosphere
AU: * Sasorova, E V
EM: sasorova_lena@mail.ru
AF: Shirshov Institute of Oceanology of RAS, Nakhimovsky prosp., 36, Moscow, 117997, Russian Federation
AU: Levin, B W
EM: levinbw@mail.ru
AF: Institute of Marine Geology and Geophysics, Far East Branch of RAS, Nauka str. 1b, Yuzhno-Sakhalinsk, 693022, Russian Federation
AB: The results of statistical analysis of worldwide seismic catalogs (ISC and NEIC), which was carried out in frame of two projects are presented. In both cases we extracted the evens occurred in the Pacific region from 1964 to 2004 with Mb>=4.0. The aftershocks were canceled from the list. All events were divided into following magnitude levels: 4<=Mb<4.5; 4.5<=Mb<5; 5<=Mb<5.5; 5.5<=Mb<6.0; 6<=Mb. The events in each magnitude level were subdivided into two groups: shallow events (H<=Htr) and deep events (H>Htr), where Htr is threshold value of the EQ source depth. In frame of the first project statistical verification of hypothesis about within-year variability existence for the events of various energy levels was carried out for the Pacific region (PO). The whole PO was subdivided into 31 subregions (Japan, Kuril Islands, Kamchatka, Aleutian Islands, Alaska, California, and so on along the perimeter of the Pacific). Then we were checking if the distributions of the events during the year period are uniform or these distributions are non- uniform. We were testing it separately for each region, for every magnitude level and for every depth level (total number of the samples under study was 310). It was disproved the null hypothesis about uniform EQ distributions in the course of year for shallow events (with less than 2% significance level), and it was confirmed the null hypothesis for deep earthquakes. It was shown that the main maximum of the seismic activity take place in November-March (minimum of the Earth-Sun distance) for both Hemispheres and the minimum - in April. It was found by using special software procedure that the Htr boundary between the shallow and the deep events was arranged in deep 60-80 km. Thus the EQ with sources located above this boundary are affected by external (astronomical) factors, which may trigger the process of EQ generation. While the external factors don't influence on the EQ sources located below this boundary. In frame of the second project statistical verification of hypothesis about existence non-random component in time distribution of the EQ's between the northern and southern part of the Pacific was carried out. The distribution-free test (run test with significant level 1%) was used for existence proof of nonrandom component into time sequences. The time sequences of the EQ switching between the Northern and Southern parts of the Pacific region contain statistically significant nonrandom component for the events with 4.0<=Mb<6.0. Then data in each magnitude range was subdivided in two groups: the deep earthquakes (H>Htr) and the shallow earthquakes (H<=Htr, for the first time Htr=70km). It was found that nonrandom component does not exist for deep earthquakes. On the contrary it is clearly manifested in time distribution of the shallow events. It was shown also that if we try to vary Htr from 15 up to 200 km we could find the best Htr value for each magnitude level. The obtained results indicate also that external periodical factors can affect, on the process of earthquake triggering, if the depth of the earthquake focus is less than Htr. The digital model (superposition of random and periodic processes) was proposed. Thereby surface in depth of 60-80 km is the boundary of external factor influence on the Earth lithosphere.
DE: 0520 Data analysis: algorithms and implementation
DE: 0550 Model verification and validation
DE: 3215 Instability analysis
DE: 3252 Spatial analysis (0500)
DE: 3270 Time series analysis (1872, 4277, 4475)
SC: Earth and Space Science Informatics [IN]
MN: 2007 Joint Assembly