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断层旋性与地震危险性 被引量:2
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作者 郭增建 吴瑾冰 《地学前缘》 EI CAS CSCD 2001年第2期247-252,共6页
文中以“平行同旋走滑断层减震”的观点论证了兰州、北京、昆明这些位于强震活动区的大城市今后百年内不会发生 6 .5级以上地震。以“平行异旋走滑断层加震”的观点解释了西南棱形块体北边界和南边界在发生大震方面相互促进的现象。对... 文中以“平行同旋走滑断层减震”的观点论证了兰州、北京、昆明这些位于强震活动区的大城市今后百年内不会发生 6 .5级以上地震。以“平行异旋走滑断层加震”的观点解释了西南棱形块体北边界和南边界在发生大震方面相互促进的现象。对于由构造分段求震级来说 ,在遇到不同的横交断层作为分段点时 ,还需考虑将来发震时始破裂点的位置以及发震断层的旋性 ,不然就会造成对震级估计不足 ,继而成为抗震建设的潜在不安全因素。在主震后为了预报余震的强度 ,可应用物理学中的科里奥利力理论 ,应用时必须知道断层类型和旋性。对于走滑断层来说 ,左旋余震弱 ,右旋余震强。例如 1997年藏北玛尼 7.5级地震 ,余震仅为 5 .3级 ,震级偏小 ,因主震为左旋的缘故 ;1976年唐山 7.8级地震 ,余震可达 7.1级 ,因主震是右旋。对于逆断层来说 ,上盘错动方向在当地子午面左侧者余震强度大 ,在右侧者余震强度弱。据此讨论了 1999年台湾南投 7.6级大震余震强度达 7.1级是因为主震为逆断层 ,上盘向西错动。 展开更多
关键词 始破裂点 科里奥利力 余震强度 断层旋性 地震地质 地震危险
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有关昆仑山口西8.1级地震及其余震活动趋势的讨论 被引量:3
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作者 吕坚 张福平 +2 位作者 高建华 胡翠娥 黄双凤 《地震学刊》 CSCD 2002年第3期17-21,共5页
在处理了部分有关资料的基础上 ,从发震断层旋性、历史地震类比、地震活动图像变化和地震序列特征等多方面对昆仑山口西 8.1级地震的余震活动趋势进行了讨论 ,结果表明 :本次 8.1级地震的最大余震震级可能为
关键词 地震 余震活动趋势 昆仑山 断层旋性 地震类比 地震序列
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The value of MSCT in diagnosis of parotid benign tumor (An analysis of 84 cases) 被引量:1
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作者 Yue Dong Jianlin Wu Ying Ge 《The Chinese-German Journal of Clinical Oncology》 CAS 2010年第6期349-353,共5页
Objective:The purpose of the study was to assess diagnostic performance of MSCT images in patients with parotid benign tumors and provide useful criteria for the characterization of their various pathological types pr... Objective:The purpose of the study was to assess diagnostic performance of MSCT images in patients with parotid benign tumors and provide useful criteria for the characterization of their various pathological types preoperatively. Methods: Retrospectively analyzed clinical and imaging characteristics of 84 cases of pathologically confirmed primary parotid benign tumors. MSCT plain-scan and enhanced-scan were performed in all cases. After injection of 50 mL contrast material at a rate of 3.5 mL/s,spiral CT scans were obtained at arterial and venous phases with scanning delay of 30 s and 75 s,respectively. The attenuation change and enhancement patterns in the tumors were assessed. Quantitatively assess the increased CT number of the tumors in different enhanced-phases compared with the plain-scan and the ratio of increased CT number at venous phase scanning to that at arterial phase scanning also was calculated. Results:In all of 84 cases,40 cases were solitary pleomorphic adenomas,29 cases were adenolyphomas,6 cases were multiple tumors,2 cases were bilateral,15 cases were Basal cell tumor,and one of them had two small lesions. The diameter was 1–5 cm in most of cases,whose margin was smooth and clear,cystic changes in some cases. At two-phase scans,pleomorphic adenomas showed a pattern of slight enhancement and venous enhancement,adenolymphomas showed a pattern of strong enhancement at arterial phase scanning with a decrease at venous phase scanning,basal cell tumor showed a pattern of persistent strong enhancement with commonly significant cystic areas. The ratio of increased CT number was significant different between adenolymphomas and other pathological types. Conclusion: The evaluation of enhancement patterns at two-phase enhanced-scan MSCT is helpful in the differential diagnosis of parotid gland benign tumors. 展开更多
关键词 parotid gland benign tumor computer tomography
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