【摘要】 对中国大陆具备相对完整资料的327次M≥5.0地震,分5个工作区进行了统一要求的地震条带图像扫描,发现96次中强震前存在条带图像,约占研究地震总数的29%.其中震前有条带地震与研究地震的比例分别为:华北地区30%,华东南区29%,川滇地区41%,青藏高原西北缘24%,新疆地区16%.中强震前出现条带比例最低的是新疆,最高的为川滇地区.在此基础上着重分析了条带形成后发生的主震与条带形成持续的时间、条带长轴尺度及组成条带地震震级等的统计关系.其结果为:中国大陆lgt(月)=0.30M-1.03±0.38(M≥6.5),lgL(km)=0.11M+1.73±1.75(M≥5.5);川滇地区lgt(月)=0.20M-0.25±0.24,lgL(km)=0.12M+1.75±0.16(M≥5.5).其它分区关系离散,未提出相应的统计关系.研究表明,条带的持续时间和条带的长轴尺度与主震震级在M<5.5时两者没有显著的相关性,而在M≥5.5时则存在一定的线性关系,但其相关性较差.组成条带的起始震级在5级(M5.0—5.9)主震前为ML2.5左右;6级(M6.0—6.9)主震前为ML3.0左右;7级(M≥7.0)主震前为ML4.0左右.主震发生在条带端部的比例大于内部;主震前出现交汇条带较少,仅占10%,主要出现在7级以上地震前.5级、6级和7级地震前出现条带的比例分别为25%、38%和71%.这个比例一定程度上表明了条带图像可能是7级以上强震的重要异常判据.更多还原

【Abstract】 327 M≥5.0 earthquakes with relatively integrated data are investigated. The whole seismic area in Chinese mainland is divided into 5 study regions. We spatially scanned the data in each region for seismic belt pattern with a uniform criterion. It is found that the belt pattern exists before 96 moderate-strong earthquakes, being 29% of the total earthquakes. The ratio of earthquakes with pre-earthquake belts over total is 30% for North China region, 29% for southeastern China, 41% for Sichuan-Yunnan region, 24% for northwest marginal region of Qingzang plateau, and 16% in Xinjiang region. The ratio for Xinjiang region is the lowest and that for Sichuan-Yunnan region is the highest. Then we statistically analyzed the relationship between the magnitude M of the mainshock, occurred after belt formation, and the belt parameters, such as belt duration time t, belt length L, and the magnitude M of belt earthquakes. The results are lg t(month)=0.30M-1.03±0.38 (M≥6.5) and lg L(km)=0.11M+1.73±1.75 (M≥5.5) for China mainland earthquakes, and lg t(month)=0.20M-0.25±0.24 and lg L(km)=0.12M+1.75±0.16 (M≥5.5) for Sichuan-Yunnan region. Due to less sample earthquakes and large data scattering, the relationships for other regions are not presented. Our study result indicates that no significant correlation exists between the mainshock magnitude M and the belt duration time t, and the belt length L, when the belt earthquake magnitude M<5.5. When M≥5.5, a linear relation would exist, but with poor data correlation. The lowest magnitudes of belt earthquakes are about ML2.5, ML3.0 and ML4.0 for the M5.0—5.9, M6.0—6.9 and M≥7.0 mainshock, respectively. The mainshocks occurred at the belt terminals are more than those occurred inside the belts. Only 10% mainshocks are associated with crossing belts, and they are mainly M≥7.0 earthquakes. The ratios of belts appeared before M5.0—5.9, M6.0—6.9 and M≥7.0 mainshocks are 25%, 38% and 71%, respectively, showing that the seismic belt pattern may be an important abnormal precursory for M≥7 .0 mainshocks.更多还原