Poster of the Carlsberg Ridge Earthquake of 15 July 2003 - Magnitude 7.6

Tectonic Summary

This earthquake occurred on the Carlsberg Ridge, a mid-ocean ridge system that is located in the Arabian sea between India and Northern Africa. The ridge marks the boundary between the Indian and African plates. Near the epicenter the Indian plate is moving away from the African Plate at a rate of 33 mm/yr in a northeasterly direction. The Carlsberg Ridge is a slow-spreading ridge with rough topography and a depth that varies from 1700-4400 meters.

Mid-ocean ridges are divergent plate boundaries, where two tectonic plates move apart from each other. New oceanic crust is formed as magma rises up between the two diverging plates. Active spreading ridges are offset by zones known as transform faults, where plates slide horizontally past each other neither destroying or forming crust. This gives the plate boundary a zigzag pattern. Ocean ridges represent the longest, linear uplifted features of the Earth's surface and are marked by a belt of shallow earthquakes. Earthquakes can be caused by the release of tensional stress in the uplifted ridge or by the horizontal movement of plates along the transform faults.


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