AN APPARENT SHEAR ZONE TRENDING NORTH-NORTHWEST ACROSS THE MOJAVE-DESERT INTO OWENS-VALLEY, EASTERN CALIFORNIA

Strain rates measured at four geodetic networks in eastern California situated between northern Owens Valley and the Transverse Ranges along a small circle drawn about the Pacific‐North America pole of rotation are remarkably consistent. Each exhibits 0.14 μrad/yr simple right‐lateral engineering‐shear‐strain accumulation across the local vertical plane tangent to the small circle. Local faults (e.g., Owens Valley, Garlock, Helendale) traversing these networks are not as closely aligned with the vertical planes of maximum shear‐strain accumulation as is the local tangent to the small circle. A fifth network slightly east of the small circle shows no significant strain accumulation. Thus, a shear zone trending N35° W from near the eastern end of the big bend of the San Andreas fault to northern Owens Valley is indicated by these data. This corresponds to the Eastern California shear zone proposed on geological evidence by Dokka and Travis. The shear zone carries ∼8 mm/yr of the Pacific‐North America relative plate motion from the San Andreas fault north‐northwest across the Mojave Desert into Owens Valley and the northern Basin and Range province. The shear zone observed at the surface may be a manifestation of a through‐going subcrustal fault. Copyright 1990 by the American Geophysical Union.