**7. The OSC area in the north half of the Sakhalin Island**

We select this area within the interblock zone dividing Japanese-Korean and Okhotsk blocks (**Figure 6**). Its length is 530 km, width – 154 km, the total seismic energy releasing after instrumental measuring data (NEIC2017) reaches 1.15535·1016J. The energy level in the central part of the area is about 1011J. Epicenters with M4–5 are numerous, with 6–8 are only single. This interblock zone stretches through all island, but in its south half is "absorbed" by the Pacific subduction zone dipping under Eurasia [1].

Longitudinal right-lateral slips with north-northeast thrust component predominate in the up-to-date structure of the north Sakhalin. Hypocenters in the crust (10-40 km) correspond to the dip slip in the island east and to thrusts in the west. The intensive earthquakes with M7.2 in Moneron (1971) and Neftegorsk (1995) occurred in northeast Sakhalin within its coastal part. Their hypocenters depth reaches 30-60 km. North Sakhalin GPS vectors direction is about 130° SE with

**11**

**8. Conclusion**

**Figure 6.**

*Tentative Intracontinental Seismic Activity in South Siberia and Russian Far East*

velocities 18.1–22.1 mm/y. After measuring in the ITRF2014 System on Khabarovsk and Seoul stations the Japanese-Korean Block moves on 115–120° SE with velocities 22-25 mm/y. This block also turns clockwise to southeast with the velocity of 0.9–1.5 mm/y according with measuring in the Sikhote-Alin geodynamic net [29]. This turn can evoke up-to-date extension and crust non-consolidation in northeast China within the Songliao Depression [30] differ from main lithosphere plates displacing by their kinematics. The Okhotsk Block displaces on 149° SE with the velocity 22.9 mm/y, North Japanese – on 132° SE with the velocity 25.0 mm/y. In the central part of the Honshu Island, the uplift fixes with the velocity 3.7 mm/y after ITRF2014. The Pacific Plate moves relatively Eurasia on 288°NW with the velocity

*The OSC area in the north half of the Sakhalin Island situates within the seismic active interblock zone dividing* 

The HF average value in Sakhalin Island is 76 μW/m−2 increasing within adjacent aqyatories up to 123-200 μW/m−2 [31, 32]. After the same authors magnetic field anomalies within island do not exceed 0-200*n* sharply increase in the Okhotsk Sea up to 1000-1200*n*. Gravitational anomalies on Sakhalin in the Bouguer reduction come to −30 - +50mGal [15]. The crust thickness under island reaches 30-35 km, the lithosphere thickness – 52 km [31]. Completing the examination of the north Sakhalin OSC area we can expect the probably origin of earthquakes with M up to 7–8 in the center of the island north part within the Neftegorsk Region, as well as west and southwest from it. For the more south regions of OSC area and the extreme north of the island we can, with certain care, suppose, that M of future seismic events will be not higher than 5–6. Hypocenters concentrations situate at the depth 5-55 km.

We selected five OSC areas in intracontinental interblock zones, in which the most intensive seismic events can take place. The OSC areas with maximal seismic activity divide the Altai Block and NEP, Hangay and Sayany blocks,

*DOI: http://dx.doi.org/10.5772/intechopen.95073*

75 mm/y in the NNR\_NUVEL\_1A System.

*Japanese-Korean and Okhotsk blocks. See summary legend for Figure 1.*

*Tentative Intracontinental Seismic Activity in South Siberia and Russian Far East DOI: http://dx.doi.org/10.5772/intechopen.95073*

#### **Figure 6.**

*The OSC area in the north half of the Sakhalin Island situates within the seismic active interblock zone dividing Japanese-Korean and Okhotsk blocks. See summary legend for Figure 1.*

velocities 18.1–22.1 mm/y. After measuring in the ITRF2014 System on Khabarovsk and Seoul stations the Japanese-Korean Block moves on 115–120° SE with velocities 22-25 mm/y. This block also turns clockwise to southeast with the velocity of 0.9–1.5 mm/y according with measuring in the Sikhote-Alin geodynamic net [29]. This turn can evoke up-to-date extension and crust non-consolidation in northeast China within the Songliao Depression [30] differ from main lithosphere plates displacing by their kinematics. The Okhotsk Block displaces on 149° SE with the velocity 22.9 mm/y, North Japanese – on 132° SE with the velocity 25.0 mm/y. In the central part of the Honshu Island, the uplift fixes with the velocity 3.7 mm/y after ITRF2014. The Pacific Plate moves relatively Eurasia on 288°NW with the velocity 75 mm/y in the NNR\_NUVEL\_1A System.

The HF average value in Sakhalin Island is 76 μW/m−2 increasing within adjacent aqyatories up to 123-200 μW/m−2 [31, 32]. After the same authors magnetic field anomalies within island do not exceed 0-200*n* sharply increase in the Okhotsk Sea up to 1000-1200*n*. Gravitational anomalies on Sakhalin in the Bouguer reduction come to −30 - +50mGal [15]. The crust thickness under island reaches 30-35 km, the lithosphere thickness – 52 km [31]. Completing the examination of the north Sakhalin OSC area we can expect the probably origin of earthquakes with M up to 7–8 in the center of the island north part within the Neftegorsk Region, as well as west and southwest from it. For the more south regions of OSC area and the extreme north of the island we can, with certain care, suppose, that M of future seismic events will be not higher than 5–6. Hypocenters concentrations situate at the depth 5-55 km.
