Abstract
Characteristics of the horizontal strains during the period 1931-1973∼75 and the earthquake occurrence during the period 1931-1978 in the Izu Peninsula are investigated, and the relation between them is studied. In addition, some features of mean crustal deformation associated with earthquake occurrence are discussed.
The horizontal crustal deformations during this period in the Izu Peninsula are characterized by the accumulation of shear strains. The strains are consistent with those resulting from earthquakes in a region where many earthquakes have occurred, but on the whole the contribution of earthquakes has been small.
The cause of the accumulation of shear strains in the Izu Peninsula in this period may be attributed to the fact that the tectonic displacement of the Izu Peninsula to the west is larger in the southern part than that in the northern part.
The horizontal strains obtained by successive triangulation measurements reflect not only the elastic strains which have accumulated but also include strains caused by earthquakes which occurred during the successive measurements and also anelastic strains. The interrelations among these deformations are briefly discussed.
