Exercise 3. Converting magnitudes
Catalogs may report magnitudes of different kind, e.g., mb, Ms, Mw, etc., that measure earthquake size. To avoid ambiguities, the question of calibrating these measures to a single one, adequate for the study considered, should be resolved first of all.
1) Run CompiCat: Click Open button in the horizontal File bar at the top. Open the file ...\ecp\exercises\ex3convertmags.csf. The catalog reports the two magnitudes - m1 of the mb type and m2 of the Ms type.
2) Click Convert magnitudes button in the vertical Tools bar on the left. Leave m1 and m2 intact, while (i) filling m3 with the minimum of m1 and the result of conversion of m2 into mb type and (ii) filling m4 with the maximum of m2 and the result of conversion of m1 into the Ms type.
For conversions use the equations mb = 0.4 Ms + 3.2
and Ms = 2.49 mb − 7.96 (Zobin, 1999). Avoid using absent magnitude values,
which are zeros in the input, by choosing the magnitude cutoffs equal
3) Save the resulting catalog as ex3converted in the ...\work directory.
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