Seismic activity triggered by stress changes after the 1978 events in the Asal Rift, Djibouti

Following a sequence of earthquakes in the Asal Rift in November 1978, the deformation resulting from dyke emplacement and associated faulting was measured geodetically and using teleseismic data. Using this information we have computed the resulting Coulomb stress changes, which can explain the features of the distribution of seismicity for the following six weeks. A further major shock then occurred. When this event is included in the modelling, the distribution of all the seismicity within a radius of 40 km in the following 4 years is predicted. The study confirms that increases of Coulomb stress as small as 0.3 bars are sufficient to trigger earthquakes and shows that dykes as well as fault slip can result in stress changes that influence the seismicity distribution over a broad region.