168 



ga|)ing are the surfixce expression of velocity-differences in a liorizontal 

 direction; horizontal transverse faults prevail at greater depth, while 

 with increasing plasticity' deformation takes place without fracture- 

 movements. If these tectonic zones of diffei-enf depths are all visible 

 at the snrface, they enable us to trace the movement for a considerable 

 space of time, because then the different phases of the movement 

 are observable. If the movements are still going on, the epicentra 

 of earthquakes will be accumulated near the places with considerable 

 velocity -differences and may be disposed along more or less transverse 

 fractures. In this connection we point to the region in the neigh- 

 bourhood of Snnda Strait between Java and Sumatra, to the earth- 

 quake lines near the bending-point between the Alps and the 

 Carpathian mountains, to Cook-strait between the Northern and the 

 Southern island of New Zealand and to many others. 



■ Azo 



-^^■;y V 



;*7<*-' 



•. Slf a'lit.- Jl manclie 



;j\eeeny:ion 



(.■■■ 



«.yji. 



'VrWlan ■■' 

 ^i Cun?i,'& 



Zuid Amerika = South America. 

 Afrika = Africa 

 Fig. 1. 2978 etc. Depths of the sea in meters on the Central-Atlantic Ridge. 



Romanche diep = Romanche Deep. 

 Azoren = Azores 



If a submarine ridge has a bending-point, the strongly curved 

 shape of the ridge may have been developed from an originally 

 simpler form by velocity-differences in a horizontal direction. Where 

 the velocity-differences are greatest, the epicentra of earthquakes 

 will be numerous, and from an accumulation of epicentra near a 



