Surfactant and water migration in unsaturated sand

• 1 In unsaturated coarse disperse materials such as sand, the water on the surface is continous and ‘deep’ enough to be an adequate medium for the migration of surface active substances (SAS).
• 2 The influence of the tangential force on water migration in unsaturated coarse disperse material is studied by compensating the capillary pressure difference caused by the surface tension gradient.
• 3 The influence on water migration in unsaturated disperse materials exerted by the additional pressure difference, originating from SAS migration, is comparable to that exerted by capillary pressure difference.

     

State of stress and intraplate earthquakes in the United States

Recently compiled data on the state of stress have been used to define stress provinces in the conterminous United States in which the orientation and relative magnitude of the horizontal principal stresses are fairly uniform. The observed pattems of stress constrain mechanisms for generating intraplate lithospheric stresses. Coupled with new information on geologic structure and tectonism in seismically active areas of the Midcontinent and East, these data help to define some characteristics common to these areas and to identify key questions regarding why certain faults seem to be seismically active.