Summary

Tortoise Hill ridge incrementally grew in height during the 1992-Landers, California, earthquake. The ridge is in strike-slip terrain, within the right-lateral, Emerson fault zone. Tortoise Hill was elevated along bounding shear zones on the northeast and southwest up to 1 m as about 3 m of right-lateral shift was accommodated across the fault zone. Fortuitously, we located a group of survey points in the Tortoise Hill area that had been placed by a public utility company. Data for the measured deformation comes from a resurvey of those points and from analytical photogrammetric measurements on pre- and post-earthquake aerial photography.

• Full Text
• Plate 1 - Fracture zones and contours of change of altitude of ground in area of Emerson fault zone.
• Plate 2 - Fractures within the Emerson fault zone between Single-Tower Transmission Line Road and Tortoise Hill
• Plate 3 - -Fractures and belt of shear zones along Emerson fault at Single-Tower Transmission Line Road.
• Plate 4 - Vertical and horizontal changes in position of points along Tortoise Hill ridge.