Applicability of the new one-dimensional velocity model in Fujian and Taiwan strait region
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摘要: 通过福建及台湾海峡地区的新一维速度模型与现有华南速度模型的对比,讨论了新一维速度模型在福建地震观测台网的适用性。理论走时分析结果表明,尽管两个速度模型差异明显,但震中距在0—100 km范围内的震相理论走时相差较小,一定程度上说明两速度模型所给出的本区域地壳平均速度差异较小。对利用18次人工定点爆破记录的地震定位结果的分析表明:当震源深度不受约束时,应用华南速度模型的定位结果精度稍优于新一维速度模型;将震源深度固定为0 km后,应用新一维速度模型的定位结果精度则明显优于华南模型。对19个仙游震群序列事件进行定位的结果显示,由于华南地区速度结构的横向变化较小,应用两模型的地震定位精度结果基本相当,但新一维速度模型定位的发震时刻较华南速度模型普遍早0.61 s左右,因此使得事件定位残差显著增大。Abstract: Based on the new one-dimensional velocity model in Fujian and Taiwan strait region, we analyzed the applicability of this model used for Fujian seismic monitoring network by compared with the existing South China velocity model. Theoretical travel time comparison shows that small difference appeared within 100 km of the epicentral distance although the two velocity models seem obviously different. To some extent, this reflects the mean velocity of this region given by these two models are consistent. By choosing 18 man-made explosion events, we test the location results based on these two models. If without constrain on focal depth, location results by using the South China velocity model are slightly better than the new one-dimensional velocity model, but when we set focal depth as 0 km, precision of location results are much better for one-dimensional velocity new model. As for 19 natural earthquake events of Xianyou earthquake sequence, as a result of small velocity variation in horizontal dimension for South China region, earthquake location precision by using both models are quite close. The origin times of the events estimated by the new one-dimensional velocity model are usually 0.61 s ahead, which also result in the residuals of location error significantly higher than those by using the South China velocity model.
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表 1 华南速度模型与新一维速度模型参数对比
Table 1 Comparison between south China velocity model and new 1D velocity model
表 2 本文采用的18次人工定点爆破事件
Table 2 18 artificial explosion events used in this paper
事件
序号爆破时间 爆破位置 年−月−日 时:分:秒 北纬/° 东经/° 1 2010−09−01 01:00:13.111 25.3967 119.7143 2 2010−09−01 01:10:14.752 25.6214 119.1688 3 2010−09−11 01:00:13.284 25.0636 118.5620 4 2010−09−11 01:10:14.472 25.4707 118.0392 5 2011−08−23 01:00:16.382 25.9200 117.6387 6 2011−08−23 01:10:14.631 26.5765 118.9839 7 2011−08−28 01:00:16.746 26.8172 118.5279 8 2011−08−28 01:10:15.000 27.2877 117.6942 9 2011−08−28 04:10:14.514 25.0417 117.3357 10 2012−07−18 01:00:20.181 25.2452 117.3357 11 2012−07−18 01:10:16.253 25.7110 116.8243 12 2012−07−23 01:00:21.079 26.1632 117.6419 13 2012−07−23 01:10:17.263 26.1632 116.2853 14 2012−07−23 01:20:15.423 26.3954 115.9158 15 2012−07−29 01:00:15.499 24.0390 116.8733 16 2012−07−29 01:20:15.866 24.9327 119.7143 17 2012−07−29 04:20:15.875 25.1793 119.1688 18 2012−08−08 01:00:21.000 24.6020 118.5620 表 3 两个模型对19次天然地震事件的定位结果
Table 3 List of location results for 19 earthquakes by using two velocity models
序号 MS 发震日期 华南速度模型结果 新一维速度模型结果 发震时刻 震中位置 震源
深度
/km残差 发震时刻 震中位置 震源
深度
/km残差 年−月−日 时:分:秒 东经/° 北纬/° 时:分:秒 东经/° 北纬/° 1 3.8 2012−11−25 07:48:49.5 118.75 25.63 10.4 0.132 07:48:48.7 118.74 25.64 9.0 0.586 2 3.4 2012−11−25 17:42:39.1 118.75 25.63 18.3 0.065 17:42:38.2 118.75 25.64 19.4 0.941 3 3.3 2012−11−30 14:59:13.7 118.75 25.63 11.4 0.090 14:59:13.0 118.74 25.64 6.9 0.319 4 4.2 2013−08−03 02:43:56.5 118.75 25.63 8.1 0.088 02:43:55.5 118.74 25.63 12.8 0.240 5 3.1 2013−08−09 13:37:07.5 118.75 25.62 13.5 0.105 13:37:07.0 118.75 25.64 9.9 0.305 6 3.5 2013−08−09 13:38:41.0 118.75 25.63 6.9 0.064 13:38:40.0 118.75 25.63 12.7 0.250 7 3.8 2013−08−19 17:36:20.0 118.75 25.63 6.3 0.086 17:36:18.9 118.74 25.63 11.0 0.321 8 4.5 2013−08−23 05:02:01.3 118.75 25.63 8.0 0.076 05:02:00.3 118.71 25.65 6.6 0.300 9 3.1 2013−08−24 00:49:57.4 118.75 25.63 7.0 0.083 00:49:56.3 118.74 25.64 10.8 0.304 10 5.0 2013−09−04 06:23:26.7 118.75 25.63 12.9 0.071 06:23:26.2 118.75 25.63 9.0 0.309 11 3.4 2013−09−14 02:59:50.8 118.76 25.62 6.6 0.093 02:59:49.8 118.75 25.62 10.9 0.291 12 3.3 2013−10−18 14:05:23.5 118.75 25.63 7.2 0.091 14:05:22.4 118.72 25.64 10.7 0.281 13 4.5 2013−10−30 01:50:12.3 118.75 25.62 9.4 0.097 01:50:11.4 118.73 25.63 7.9 0.229 14 3.2 2013−11−19 03:03:59.0 118.76 25.62 6.3 0.080 03:03:58.2 118.76 25.64 9.8 0.301 15 3.1 2013−12−16 19:01:36.0 118.75 25.64 5.6 0.071 19:01:35.2 118.74 25.65 10.7 0.347 16 3.1 2014−01−27 13:50:18.8 118.74 25.64 6.4 0.093 13:50:17.9 118.73 25.65 10.7 0.278 17 3.8 2014−03−14 19:53:36.1 118.75 25.63 7.0 0.153 19:53:35.0 118.74 25.64 10.4 0.230 18 3.0 2014−05−12 18:24:00.0 118.74 25.64 7.6 0.088 18:24:18.5 118.73 25.64 11.0 0.333 19 3.3 2014−07−19 01:50:16.0 118.74 25.64 5.8 0.111 01:50:15.1 118.73 25.65 8.7 0.312 -
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