A Continental-scale Seismic Observatory


Central Oregon Locked Zone Array

Principal Investigators and Institutions:

Anne Trehu, Oregon State University

Station Map

Funding Source:

NSF EarthScope

Field Dates: 

1/2008 – 12/2010

Equipment Used:

11 Broadband Stations   

Data Status:

Archive Complete

Data released

Network Code:  



Station MapHistorically, the subducting Juan de Fuca plate has produced very large thrust earthquakes along the Cascadia subduction zone. These events occur every few hundred years on average, with very little documented seismic activity in the interim. Since 2003, about 40 earthquakes have been detected in the nominally "locked" zone offshore central Oregon. Analysis of the two largest earthquakes suggests that they were low angle thrust events on the plate boundary. We are currently operating an onshore/offshore seismic array (COLZA – Central Oregon Locked Zone Array) to better constrain microseismic activity in this region. 

The COLZA experiment consists of six temporary land seismic stations from the FlexArray, part of EarthScope's USArray network of instuments, and two deployments of ocean bottom seismometers. Our data are collected and archived with the help of the Program for Array Seismic Studies of the Continental Lithosphere (PASSCAL) and archived by the Incorporated Research Institutions for Seismology (IRIS).

Publications/ Abstracts

Tréhu, A.M., J. Braunmiller, J. L. Nabelek, Probable low-angle thrust earthquakes on the Juan de Fuca–North America plate boundary, Geology, Volume 36, Issue 2 (February 2008) pp. 127–130