1.   Earthquakes happen when stresses in rock are suddenly released as the rocks fracture.

2.   It is thought that while this force is insignificant in large voids it can be sufficiently strong in the small pores in very fine-grained material to cause rock fracture.

3.   Finally, crystallization occurs preferentially along a single crystal axis and large pressures can be generated within rock fractures.

4.   The report contained a photograph of severe rock fractures near the South Pacific test sites on Mururoa and Fangataufa.