【英语时差8,16】震波决定地震的方向和速度（下）

 And the direction the crystals are pointing makes a difference to the speed seismic¹ waves travel through the rock: a wave traveling parallel to the crystals–in other words, along the length of the toothpick–moves faster than a wave traveling in the other direction, across the width of the crystals. So if seismic waves going through one part of the earth always travel faster in one direction than they do in another, there’s a good chance that the rock there is moving in that direction. Based on this kind of information geologists² can construct models of what’s going on in parts of the earth no one has ever seen–models that show us the slow movement of molten rock, welling up from the earth’s core, escaping here and there through volcanoes, and slowly pushing the continents around on the earth’s surface.

1 seismic   

a.地震的，地震强度的

参考例句：

• Earthquakes produce two types of seismic waves.地震产生两种地震波。
• The latest seismic activity was also felt in northern Kenya.肯尼亚北部也感觉到了最近的地震活动。

2 geologists   

地质学家，地质学者( geologist的名词复数 )

参考例句：

• Geologists uncovered the hidden riches. 地质学家发现了地下的宝藏。
• Geologists study the structure of the rocks. 地质学家研究岩石结构。