在地图上画圆的方法找到他们的交集只解决了一个未知数。当站远离震源地震或虽浅,焦点和中心之间的距离之间的差别将被忽略。因为许多地震是浅,三圈经常做相交于一点。当他们不这样做,一个可能的解释是,因为地震相对深度(与震中的距离。)如果你想尝试确定震中和地震的深度,那么您需要收集更多的观察(站)和用数学来解决系统至少有两个未知数。您可以使用线性代数。注意站到达时间接近地震将受到关注的深度的影响比站远,所以你会想要包括车站靠近地震。中学物理学生可能有足够的数学使用[牛顿迭代方法][1]的方法来估计深度。他们可能会使用的初始估计的“震中”第一个方法,试图解决的约束方程来估计一个深度。在实践中,地震学家收集大量的数据,必须考虑许多未知数,如距离焦点,而且地震速度的变化通过不同类型的岩石。 If you try the three-station and map approach in your Earth Science classroom, the students may notice that all three circles do not go though a single point typically, but come more or less close to doing so. Perhaps this is a good opportunity to discuss the differences between a model and actual earthquakes and Earth. It might even be possible to discuss how a better model can improve the agreement with observations. It looks like this USGS page : [Determining the Depth of an Earthquake][2] has a somewhat different answer, which may describe how deep earthquakes were 'discovered' historically :) [1]: http://mathworld.wolfram.com/NewtonsMethod.html [2]: http://earthquake.usgs.gov/learn/topics/seismology/determining_depth.php