Not all fault slip happens in earthquakes. Many faults, including sections of the San Andreas and Calaveras faults here in central California, are known to creep: slipping slowly, either continuously or in small pulses, without shaking the ground at all. A creepmeter is a deceptively simple but extremely sensitive instrument that we install directly across a fault trace to track that slow slip at the micrometer scale, giving us a continuous, high-resolution record of how much the two sides of the fault are sliding past each other, day by day.

Measuring surface creep matters because it tells us how locked a fault segment is, which feeds directly into seismic hazard assessments, and it flags places where slow, ongoing slip could damage roads, pipelines, or any infrastructure that crosses the fault. What we still don't fully understand are the details of episodic creep events: brief accelerations of a few millimeters of slip that build up and then slowly relax back down over hours to days. How large do these events get? How far do they propagate along the fault? Are they related to the deeper, aseismic slip happening below the surface? And how much of what we record is the fault itself versus rain, temperature, or other environmental noise contaminating the signal?

To chase these questions, we are filling in the instrumental gaps along the northern edge of the central creeping section of the San Andreas fault near San Juan Bautista and along the adjacent Calaveras fault, installing new creepmeters and working on better ways to identify and remove environmental effects like rainfall from the data. This work is done in close collaboration with Prof. Roger Bilham (CIRES, University of Colorado Boulder), the genius behind the original development of these creepmeter instruments, whose decades of experience building and running these instruments around the world is at the core of this effort.

Stay tuned as we install and start streaming data from the new stations. This page will grow with pictures from the field and updates as we start resolving individual creep events along these faults.