地震简问简答/Why are there often different magnitudes reported for the same earthquake?

Q: Why are there often different magnitudes reported for the same earthquake?

为什么会经常发现同一个地震会报道成不同的量级呢？

A: When an earthquake occurs, the first information that is processed and relayed is usually based on a small subset of the seismic stations in the network, especially in the case of a larger earthquake. This is done so that some information can be obtained immediately without waiting for all of it to be processed. As a result, the first magnitude reported is usually based on a small number of recordings. As additional data are processed and become available, the magnitude and location are refined and updated. Sometimes the assigned magnitude is "upgraded" or slightly increased, and sometimes it is "downgraded" or slightly decreased.

回答：当一场地震发生时，尤其是一场大地震发生时，最先处理并传递的资料信息通常基于地震监测站网络中的一个小区域的报告。这样方便迅速快捷的处理信息，而不必等待所有数据都达到后再处理。因此，第一次报道的地震级数通常基于很小一部分的数据。当更多的附加数据处理并可用时，地震量级和发生地点便可加以精确和校正。有时，量级会升级或略微增加。有时也会降级或略微减少。

Sometimes the earthquake magnitude is reported by different networks based on only their recordings. In that case, the different assigned magnitudes are a result of the slight differences in the instruments and their locations with respect to the earthquake epicenter.

也有可能的是有时地震级数由不同的监测网依据他们各自的数据汇报而得。在这种情况下，所得到的不同的级数则是因为各监测网使用的略有不同的监测工具，并与他们相对于地震中心的位置不同有关。

For further information, see: Measuring the Size of an Earthquake

为参考更多资讯，请参见： Measuring the Size of an Earthquake