The Relation between Magnitudes MLH and MW for the Kuril–Okhotsk Region and the Use of the Relation for Conversions to Other Magnitudes

Abstract

With the purpose of unifying the earthquake catalog for the Kuril–Okhotsk region we derived a two-segment linear relation between the magnitude based on the surface wave MLH as reported by the Sakhalin Branch of the GS RAS and the moment magnitude M_W as reported by the GCMT and NIED. Comparison to analogous relations based on other catalogs shows that for large (MLH = 6.5–8.1) earthquakes there is a small (∼0.1) excess of regional magnitude MLH over the M_S in other catalogs. MLH exceeds the values of M_S by 0.2–0.4 in the interval MLH = 4.0–6.5. We have obtained relations connecting MLH and M_L as reported by the Kamchatka Branch of the GS RAS in the area of the Middle-Northern Kuril Islands, and MLH and M_j of the JMA for the southern part of the region. Conversion using the relation MLH(M_W) has repeated with good accuracy the relations derived directly. The best result is achieved when the differences between the determinations of M_W as reported by different agencies have been taken into account.