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美国中部最强烈的地震活动集中在密西西比湾北部的New Madrid地震带.从1811到1812年,在这个地震带上接连发生了三个强烈地震,据估计,其震级分别为7.2、7.1和7.4级。这一地区的地震活动一直持续到现在,其微震在空间上的分布明显地呈两个线性带(图1)。其中,主要地震带的走向为北东,与密西西比湾的轴部相平行;另外一个的走向为北西,大致与Pascola背斜的峰线相一致。这两个地震带在New Madrid附近相交叉,据推测,其位置可能与地震活动断层相对应。
The strongest seismic activity in the central United States concentrated in the New Madrid seismic zone in the northern part of the Mississippi Bay. From 1811 to 1812, three strong earthquakes occurred consecutively on this seismic belt, with an estimated magnitude of 7.2, 7.1 and 7.4, respectively . The seismic activity in this area has lasted till now, and the spatial distribution of its microseismicity obviously shows two linear bands (Figure 1). Among them, the main seismic belt to the northeast, and the Mississippi Bay axis parallel; the other for the northwest, roughly the same line with the Pascola anticline. The two seismic belts cross near New Madrid and it is presumed that their location may correspond to seismic faulting.