| Western China is located in Triangle Region of active earthquakes, where strong earthquakes bring huge losses. Searching for historical laws of strong earthquakes, accurately judging space-time tendencies of strong earthquakes and discussing their mechanisms have significant meanings to prevention and reduction of regional disasters.This paper tried to select five study areas in western China, including a large size area and four middle size areas. Using Commensurability Test, Map of Butterfly Structure (MBS), plane and steric structures of commensurability, space symmetry, etc., this paper analyzed historical regularities, characteristics of space-time symmetry, future signals and mechanisms of strong earthquakes. Results showed as follow:1) Analyses of historical strong earthquakes showed that foreign scholars were good at using methods and models to count historical earthquakes, while most domestic researches were about classification for earthquake regions, spatial-temporal distributions, algorithms and models. There were 352 Ms?6.0 earthquakes in western China from 780 B.C. to 2015 A.D.2) According to time symmetry study, Ms?7.8 earthquakes would happen again in 2022 in western China and its adjacent areas; Ms?6.9 earthquakes would happen in 2020 in Xinjiang; Ms^6.4 earthquakes would happen in 2017 in Xizang; Ms?6.6 earthquakes would happen in 2018 in Shaanxi, Gansu and Ningxia; Ms?7.2 earthquakes would happen in 2023 in Sichuan and Yunnan.3) According to space symmetry study, the Ms?.8 earthquake would migrate to the northeast direction next time in western China and its adjacent areas; the Ms?6.9 earthquake would migrate to the southeast direction next time in Xinjiang; the Ms?6.4 earthquake would move to the north of 30°N and the west of 90.5°E directions next time in Xizang; the Ms?6.6 earthquake would migrate to the southeast direction next time in Shaanxi, Gansu and Ningxia; the Ms?7.2 earthquake would migrate to the northeast direction next time in Sichuan and Yunnan.4) Mechanisms of strong earthquakes were sunspots, earth rotation, phases of the moon and plate dynamics. Relationships between sunspots and earthquakes in western China and its adjacent areas from 1755 to 2015 were:there would be more strong earthquakes in years of few sunspots than in years of many sunspots. Most strong earthquakes concentrated in years of few or many sunspots. Strong earthquakes happened more frequently during 1890-2015 than during 1755-1889 in Xinjiang, Xizang, Shaanxi, Gansu, Ningxia, Sichuan and Yunnan. Strong earthquakes happened more frequently in deceleration periods of earth rotation than in acceleration periods of earth rotation during 1900-2015, which was more obvious in Xizang. Earthquakes tended to happened in deceleration periods of earth rotation. It was more frequently for strong earthquakes to happen during the last quarter of the moon from 1900-2015 in western China and its adjacent areas, Xinjiang, Sichuan and Yunnan. Strong earthquakes tended to happen during the last quarter of the moon and Wangri in Xizang, which tended to happen during Shuori in Shaanxi, Gansu and Ningxia. Earthquakes tended to happen in western China within the next year after Ms?7.0 earthquakes in Assam from 1910-2015, during which Sichuan, Yunnan and Xizang were more likely to happen earthquakes. Except Xinjiang, earthquakes had a greater potential to happen in western China in two and three years than within the next year after Ms?7.0 earthquakes in Pamir, during which Xinjiang and Xizang were more likely to happen earthquakes. Assam and Pamir served as two northward dynamic points of India plate to tectonic deformation and earthquakes in western China. The closer the regions to India plate, the more forces on them.This research enriched space-time symmetry method system and added study cases of strong earthquakes. It would establish reference values for disaster research in the future. |
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