Multiwavelength EDM measurements in southern California

39

Tecionophysics, 91 (1983) 39 Elsevier Science Publishers

B.V., Amsterdam

MULTIWAVELENGTH

- Printed

in The Netherlands

EDM MEASUREMENTS

IN SOUTHERN

CALIFORNIA

LARRY

E. SLATER

‘, ART McGARR

2, JOHN

0. LANGBEIN

’ and MARK

F. LINKER

2

’ CIRES, University of Colorado/NOAA Boulder, Cola. (U.S.A.) ’ U.S. Geological Survey, Menlo Park, Calit (U.S.A.) (Received

March

10, 1983)

ABSTRACT

We installed a precise geodetic network along the San Andreas Pearblossom, California in November, 1980. The network is within frequently

referred

from a central measured (MWDM) protective

to as the “Palmdale

benchmark.

Uplift”

and consists

of 13 lines radiating

The lines range in length from 3.2 to 8.1 km are generally

several times each instrument is located shelter. The MWDM

week. The multiwavelength distance measuring at the central benchmark and is housed in a small instrument has demonstrated a capability to make

measurements to a precision of 1 part in 10 million. Using a coordinate system whose x-axis is parallel Andreas fault the following this effort: iXX = -0.180

k 0.025 pstr/yr

ivv = -0.031

_+0.029 pstr/yr

i,J’ = +0.077

+ 0.024 pstr/yr

A = -0.213

fault near the region

strain rates were observed

to the local trace of the San during

the first 10 months

of

f 0.039 pstr/yr

The observed strain rates do not appear to be constant in time, much of the deformation occurs in fairly well defined episodes. These changes in strain rate are particularly obvious in the iYv component.

0041-1951/83/$03.00

0 1983 Elsevier Science Publishers

B.V.