Spatial-Temporal Comparison of Distribution of Seismic Activity and Isostatic Anomalies along the Mid-Atlantic Ridge

Abstract

The structure of a spatial-temporal distribution of seismic activity along the Mid-Atlantic Ridge (MAR) according to teleseismic data is characterized by areas of increased activity that are marked on spatial-temporal cross-sections with stripes of event concentration, divided by inactive areas of low seismic activity that are marked on cross-sections with gaps. The areas with increased seismic activity matching minimums of isostasy can be interpreted as local areas of hot mantel injection reflected in gravity anomalies and seismic activity stable both over time and in position. These areas exist in the MAR segments that are characterized by a low-temperature and low-depth magmatic activity of “spreading” type. The gaps in seismic activity were observed in the areas of highly productive magmatic activity of “plume” type, where the mantle with lower viscosity and low tectonic stress is distributed. Wide stripes of high seismic activity coincide with shear fracture zones with high amplitude lateral discontinuity of MAR axis. The stripes of seismic activity matching the local maximums of isostasy can either mark transform faults, where shear type seismic events are registered, or highly productive “plume” magmatism with increased seismic activity, where the magmatic activity leads to a volcanic activity that forms sea floor peculiarities observed in gravity anomalies.

Keywords

• seismicity
• isostasy
• mid-atlantic ridge
• magmatism
• spatial-temporal anomaly