THE EVOLUTION OF SEISMIC ACTIVITY IMAGE IN THE HIMALAYA BELT BEFORE AND AFTER 2015 NEPAL M 8.1 GREAT EARTHQUAKE
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摘要: 针对2015年4月25日尼泊尔M8.1地震后喜马拉雅造山带的未来地震危险性问题,通过对喜马拉雅带历史大地震应变能释放和在尼泊尔地震发震前后的区域地震活动图像进行了分析研究。结果发现喜马拉雅带很可能已进入新-轮的地震活跃期。此次尼泊尔大地震不足以将喜马拉雅带中段的地壳应变能全部释放,喜马拉雅带中段的地震活动和藏南裂谷带地震活动具有密切的关联,在喜马拉雅带中段和藏南裂谷带还将有大地震活动。同时研究结果还显示现今在喜马拉雅带的东段存在阿萨姆围空区和不丹围空区,在喜马拉雅的西段出现噶尔围空区,喜马拉雅西段新德里和西藏接壤地区以及喀喇昆仑断裂上噶尔县地区地震危险性很高,喜马拉雅东段林芝山南地区以南的阿萨姆和不丹地区危险性很高,应引起重视。Abstract: Concerning on the future seismic risk brought by Himalaya orogenic belt after the April 25th, 2015 M8.1 Nepal earthquake, we analyze the strain energy release of Himalaya belt historical great earthquakes and study the regional seismicity images of both pre and post Nepal earthquake. The results show that Himalaya belt may has entered a new round of seismic active period. Crustal strain energy in the middle section of Himalaya belt didn't release completely in this earthquake, the earthquake activity is closely associated between the middle section of Himalaya belt and South Tibet Rift zone, there will be great earthquakes occurring in these two places. Assam gap zone and Bhutan gap zone exist on the east segment of Himalaya belt, meanwhile, Gar gap zone exists on the west, the border region of New Delhi and Tibet in western Himalaya belt and the Gar county area on the Karakorum fault have high seismic risk, Assam and Bhutan in southern Nyingchi, Shannan in eastern Himalaya belt also have high seismic risk, so these zones should be paid more attention to.
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Key words:
- seismic strain energy release /
- seismic empty segment /
- seismic gap zone /
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图 1 青藏高原及邻区主要活动断裂与历史地震分布图(喜马拉雅弧大地震及空段资料引自Bilham[4, 7],Avouac[5];编号1—9的藏南地震指示由喜马拉雅大地震触发的强震;Ⅰ—Ⅹ代表Bilham预测的地震位置及震级)
①—错那-沃卡裂谷;②—亚东-谷露裂谷;③—定结-申扎裂谷;④—岗嘎-当惹雍错裂谷;⑤—聂拉木-措勤裂谷;⑥—仲巴-改则裂谷;⑦—公珠错-亚热裂谷;⑧—普兰-革吉裂谷;MFT—喜马拉雅主前缘逆冲断裂带;KKF—喀喇昆仑断裂带;GCF—格仁错断裂;BCF—崩错断裂;LCF—龙木错断裂;KXF—康西瓦断裂带
Figure 1. Main active faults and historical earthquakes in Tibet Plateau and its adjacent areas
表 1 历史记录的喜马拉雅MFT上大地震触发藏南地区强震事件一览表
Table 1. Strong earthquake events with historical records at south tibet trigerred by great earthquakes on MFT
喜马拉雅MFT上的大地震活动 触发的藏南地区M≥6.8强震活动 时间 震级 宏观位置 时间 震级 宏观位置 发震构造 编号 1400年 >8.0 克什米尔 1411年9月 8.0 当雄—羊八井 亚东—谷露裂谷北段 1 1803年9月 7.5 尼泊尔西部 1806年6月 7.5 错那 错那—沃卡裂谷南段 2 1871年6月 7.5 西藏错那—洛扎一带 1883年10月 7.0 普兰 普兰—革吉裂谷南段 3 1897年6月 8.7 印度西隆高地 1901年4月 6.8 尼木 亚东—谷露裂谷中段 4 1905年4月 8.0 克什米尔 1909年8月 6.8 浪卡子 亚东—谷露裂谷中段 5 1915年12月 7.0 桑日 错那—沃卡裂谷北段 6 1934年1月 8.1 尼泊尔东部 1934年12月 7.0 申扎东北 果忙错地堑 7 1950年8月 8.6 西藏察隅与印度 1951年8月 8.0 那曲—当雄交界 崩错断裂带 8 阿萨姆邦交界 1952年8月 7.5 那曲县桑雄 亚东—谷露裂谷北段 9 表 2 围空区信息及地震危险性一览表
Table 2. Information of the seismic gap zone and earthquake risk
编号 空区名称及围空震级 长轴/km 短轴/km 面积/104 km2 长轴走向 围空时间/a 潜在发震断层 潜在震级 危险程度 1 尼泊尔地震围空区(Ms≥6.0) 550 250 11.2 北东—南西 81已发震,Ms8.1,2015-04-25 喜马拉雅带中段; 8.0~8.5 高 定结—申扎裂谷;岗嘎—当惹雍错裂谷;聂拉木—措勤裂谷;仲巴—改则裂谷;格仁错断裂;崩错断裂 6.5~7.5 高 2 噶尔围空区(Ms≥6.0) 526 276 11.14 北西—南东 78 喜马拉雅带西段 8.0~8.5 高 喀喇昆仑断裂 7.0~8.0 高 3 阿达姆围空区(Ms≥6.0) 236 150 2.84 东西 65 喜马拉雅带东段 7.5~8.5 高 4 不丹围空区(Ms≥5.0) 1.68 近东西 74 喜马拉雅带东段 7.0~8.0 高 -
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