Matching satellite‐derived gravity signatures and seismicity patterns along mid‐ocean ridges

A world‐wide correlation between satellite‐derived gravity signatures and the relative abundance of teledetected earthquakes over mid‐ocean ridges has yielded some unexpected results. Rift valley disappearances along slow‐spreading centres and attendant excess volcanism coincide with seismicity gaps, at times related to nearby hotspots, whereas earthquake clusters along virtually aseismic, faster‐spreading centres systematically indicate the presence of active propagating ridge tips. Therefore, at the world scale of investigation, seismicity fairly well predicts ridge morphology and 2nd order axial discontinuities. The occurrence of a certain degree of seismicity along the ‘ductile’ Reykjanes ridge south of the Iceland hotspot is tentatively explained in terms of prevailing shear stresses due to oblique spreading which accumulate on the available brittle volume on the flanks of the ridge rather than on its crest.