Calculations of b Value in Qaidam Basin—Altun Seismic Belt
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摘要: 目前工程地震中使用的b值来源于《中国地震动参数区划图》(GB 18306—2015),地震资料仅考虑至2010年,距今有10多年的地震资料缺失,在此期间柴达木—阿尔金地震带发生了7级以上强震,因此需验证该地区b值是否体现高震级段地震危险性水平。为此,利用1920—2019年地震资料,对柴达木—阿尔金地震带b值进行统计研究,确定b值为0.76。根据该地震带不同构造区提取地震目录,按照震级完整时段计算各自b值,得到b值范围为0.536 5~0.801 9,最大差值为0.272 6,该结果低于《中国地震动参数区划图》(GB 18306—2015)确定的b值,体现了近期大地震的发生对该地震带活动强度和大震重现期等地震活动特征和活动水平的影响,本研究确定的b值可作为《中国地震动参数区划图》(GB 18306—2015)的补充,可为科学建立重大建设工程地震危险性计算模型提供基础依据。
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关键词:
- 柴达木—阿尔金地震带 /
- b值 /
- 最小二乘法 /
- 构造区
Abstract: At present, the b value used in engineering earthquakes comes from GB 18306—2015 "Seismic ground motion parameters zonation map of China". The seismic data for deriving b value is by 2010, and there has been an accumulation of seismic data for 10 years. A strong earthquake of magnitude 7 or more occurred during the period, therefore it is necessary to verify whether the b value in this area can reflect the seismic hazard level of the high-magnitude section. In this paper, based on seismic data in 1920—2019, the b value of the Qaidam—Altun seismic belt was calculated and analyzed, and the b value was determined to be 0.76. The earthquake catalogue was extracted according to the different structural areas of the belt, and the respective b values were calculated according to the full period of magnitude. The range of b values is (0.5365~0.8019), and the maximum difference is 0.272 6. The result is lower than the b value determined by GB 18306—2015, which reflects the impact of recent large earthquakes on the seismic activity intensity and return period of the seismic belt and other seismic activity characteristics and activity levels.As a supplement to GB 18306—2015, the b value determined in this paper can provide a scientific basis for the establishment of seismic hazard calculation model of major infrastructure.-
Key words:
- Qaidam Basin—altun seismic belt /
- b value /
- Least squares method /
- Structural areas
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表 1 柴达木—阿尔金地震带1920—2019年M≥6.0地震目录
Table 1. Earthquake catalog M≥6.0 of Qaidam—Altun Seismic belt from 1920 to 2019
发震时间/(年-月-日) 震中位置 震级/M 震源深度/km 参考地名 纬度/° 经度/° 1922-10-17 39.50 91.0 6½ — 若羌罗布泊东南 1924-07-03 36.96 84.4 7¼ — 民丰东 1924-07-12 37.10 83.6 7¼ — 民丰东部 1927-03-16 38.20 98.2 6 — 青海哈拉湖东 1930-07-14 38.10 98.2 6½ — 青海哈拉湖东 1933-09-26 38.27 86.9 6¾ — 且末东 1938-08-23 37.40 98.5 6 — 青海天梭西 1941-04-19 39.10 97.0 6 — 青海玉门附近 1951-12-27 39.60 95.7 6 — 甘肃肃北东 1952-10-06 37.10 93.2 6 — 青海乌图美仁附近 1962-05-21 37.10 96.0 6¾ 25 青海北霍布逊湖附近 1977-01-02 38.21 91.21 6.4 33 青海 1977-01-19 37.10 95.81 6.3 18 青海 1987-02-26 38.46 91.36 6.1 24 青海茫崖西北 1990-01-14 38.39 91.57 6.7 12 青海 1990-04-26 36.08 100.08 7.0 9 青河共和西南 1993-10-02 38.31 88.69 6.6 27 若羌 1994-01-03 36.10 100.10 6.0 8 青海南 2000-09-12 35.30 99.30 6.6 10 青海兴海—玛多 2003-04-17 37.50 96.80 6.6 15 青海德令哈 2008-03-21 35.67 81.52 6.1 33 于田 2008-03-21 35.60 81.61 7.3 33 于田 2008-11-10 37.60 95.90 6.3 10 青海海西 2009-08-28 37.60 95.90 6.6 10 青海海西 2009-08-31 37.74 95.98 6.1 7 青海海西 2012-08-12 35.90 82.50 6.2 30 于田 2014-02-12 35.99 82.46 6.0 7 于田 2014-02-12 36.10 82.50 7.3 12 于田 表 2 余震时间窗
Table 2. Aftershock time window
震级范围 T/d 4.0≤M<4.5 42 4.5≤M<5.0 83 5.0≤M<5.5 155 5.5≤M<6.0 290 6.0≤M<6.5 510 6.5≤M<7.0 790 表 3 2008年于田7.3级地震余震删除前、后地震数
Table 3. Earthquakes before and after the deletion of Yutian M7.3 earthquake in 2008
2008年于田7.3级
地震资料不同震级范围的地震数 4.0≤M<4.5 4.5≤M<5.0 5.0≤M<5.5 5.5≤M<6.0 6.0≤M<6.5 6.5≤M<7.0 7.0≤M<7.5 原始 85 40 28 5 2 0 1 删除余震后 34 10 7 0 0 0 1 表 4 地震带地震目录余震删除前、后地震数
Table 4. Earthquakes before and after the deletion of aftershock
柴达木—阿尔金地震带
1920—2019年地震资料不同震级范围的地震数 4.0≤M<4.5 4.5≤M<5.0 5.0≤M<5.5 5.5≤M<6.0 6.0≤M<6.5 6.5≤M<7.0 7.0≤M<7.5 原始 481 209 125 42 14 9 5 删除余震后 330 145 92 32 11 9 5 表 5 不同构造区地震目录
Table 5. Earthquake catalog of different structural areas
柴达木—阿尔金地震带
1920—2019年地震资料不同震级范围的地震数 4.0≤M<4.5 4.5≤M<5.0 5.0≤M<5.5 5.5≤M<6.0 6.0≤M<6.5 6.5≤M<7.0 7.0≤M<7.5 原始 481 209 125 42 14 9 5 删余震后 330 145 92 32 11 9 5 表 6 不同构造区不同起算震级计算b值
Table 6. Calculation of b-values with different starting magnitudes in different structural areas
地区青海湖地震构造区 柴达木地震构造区 阿尔金地震构造区 a b a b a b 起始震级4.0级 3.493 2 0.536 5 4.908 0 0.668 1 5.560 3 0.801 9 起始震级5.0级 3.403 8 0.506 0 — — 4.900 5 0.676 8 -
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