(1) |

The relationships in question are

(2) |

following Bowers and Hudson (1999) and others (for references see Müller 2001), and

(3) |

following Müller (1973) and equivalent formulae for the seismic far-field derived by Wielandt (1972, 1975). Both formulae have been applied to spherical sources; however for eq. (2) gives a larger source volume than eq. (3). The apparent inconsistency has not fully been resolved in Müller's note; he shows however that (2) applies to the moment-tensor equivalent of a crack and (3) to the moment-tensor equivalent of a spherical explosive source.

2003-05-30