WE PLAN TO STUDY EARTHQUAKE HAZARD ALONG THE CASCADIA REGION OF THE PACIFIC NORTHWEST BY DETERMINING FROM SPACEBORNE INSAR DATA IF ASEISMIC OR SILENT SLIP ALONG THE PLATE BOUNDARY IS AFFECTING THE EARTHQUAKE RISK. FOR THE PAST DECADE AND A HALF WE HAVE KNOWN THAT SLOW SLIP EVENTS ALSO KNOWN AS SSES OR EPISODIC TREMOR AND SLIP (ETS) OCCUR IN THIS REGION AND ALONG SIMILAR SUBDUCTION BOUNDARIES WORLDWIDE. WHILE THE SEISMIC EVENTS WE CALL EARTHQUAKES MAY LAST FROM A FEW SECONDS TO OVER A MINUTE AN SSE MAY UNFOLD OVER HOURS DAYS OR EVEN WEEKS. AS SUCH THEY ARE NOT EVIDENT IN MOST SEISMOGRAPH OBSERVATIONS BUT THEY CAN BE DETECTED IN CRUSTAL DEFORMATION MEASUREMENTS. THE GROUND ACCELERATION FROM VERY SLOW MOVING WAVES IS TINY SO THAT THE EVENTS THEMSELVES ARE MUCH LESS HAZARDOUS TO STRUCTURES THAN THEIR MORE RAPID EARTHQUAKE COUSINS. NONETHELESS THE TOTAL MOMENT RELEASED IN AN SSE MAY BE QUITE LARGE AND STRESS TRANSFER FROM THE EVENT MAY EITHER INCREASE OR RELAX STRAIN STORED ELASTICALLY IN A FAULT OR SUBDUCTION BOUNDARY. THUS IT IS IMPORTANT FROM A HAZARD VIEWPOINT TO UNDERSTAND THE NATURE AND IMPACT OF THESE OFTEN REGULARLY-REPEATING AND PREDICTABLE EVENTS AND WHETHER THEY ARE ADDING TO HAZARD POTENTIAL OR AMELIORATING IT. SSES WERE FIRST APPRECIATED IN GPS NETWORK OBSERVATIONS AS LARGE SCALE DISTORTIONS OF THE EARTH S SURFACE. SSE MAPS TO DATE ARE AVAILABLE ONLY IN AREAS WITH RATHER DENSE GPS INSTRUMENTATION AND EVEN SO OFTEN THE NETWORK IS TOO SPARSE TO LOCALIZE THE SUBSURFACE SLIP SUFFICIENTLY TO DETERMINE ITS IMPACT ON HAZARD. INSAR PROMISES A MEANS TO MEASURE CRUSTAL DEFORMATION REMOTELY WITH SPATIALLY DENSE MEASUREMENTS EVEN IN AREAS WITH NO GROUND GPS RECEIVERS. THE CHALLENGE OF SUCCESSFULLY IMPLEMENTING INSAR OVER CASCADIA IS THAT THE DENSE FOREST COVER LEADS TO SIGNIFICANT INSAR DECORRELATION. WE WILL USE IMPROVED PERSISTENT SCATTERER (PS) POINT IDENTIFICATION INTERPOLATION OF THE SPARSE PHASE FIELD INVERSE SOLUTIONS OPTIMIZED FOR TRANSIENT DETECTION AND SEPARATION OF THE SECULAR AND TRANSIENT SIGNALS WHICH WHEN BROUGHT TOGETHER WITH SPECIFIC IMPROVEMENTS FOR THE LOCAL CASCADIA ENVIRONMENT ARE A NEW AND UNTESTED EFFORT THAT MAY ALLOW FOR A SUPERIOR ASSESSMENT OF THE HAZARD POTENTIAL OF A MASSIVE EARTHQUAKE IN THE PACIFIC NORTHWEST. THIS WOULD BE TO OUR KNOWLEDGE THE FIRST IMPLEMENTATION OF THE TYPE OF HAZARD ANALYSIS FROM CRUSTAL DEFORMATION THAT HAS BEEN SHOWN IN HAWAII AND MEXICO TO AN ENVIRONMENT WHERE THE SURFACE IS HIDDEN BENEATH A VERY THICK VEGETATION CANOPY. WE PROPOSE TO PRODUCE SPATIALLY DENSE CRUSTAL DEFORMATION OBSERVATIONS THAT WHEN USED WITH THE EXISTING GPS AND SEISMIC DATA CAN LOCALIZE AND ASSESS THE SIZE OF SLOW DISPLACEMENTS ON THE PLATE SUBDUCTION BOUNDARY. WE WILL MEASURE SSE CRUSTAL DISPLACEMENTS IN CASCADIA USING INSAR AND SOLVE FOR A MODEL OF THE SLIP AT DEPTH THAT HELPS US UNDERSTAND THE POTENTIAL FOR A LARGE AND DESTRUCTIVE EARTHQUAKE. WE WILL USE A COMBINATION OF INSAR MEASUREMENT AND DATA INVERSION TECHNIQUES THAT WE AND OTHERS HAVE DEVELOPED OVER THE PAST FEW YEARS TO OBTAIN ACCURATE CRUSTAL DEFORMATION MAPS WITH WIDE GROUND COVERAGE SEPARATE THE SSE SIGNATURES FROM THE SECULAR BACKGROUND MOTIONS AND INTERPRET THE SOLUTIONS AS SLIP AT DEPTH WITH SUFFICIENT LOCALIZATION TO ASSESS THE INCREASE OR DECREASE TO HAZARD POTENTIAL FROM THESE EVENTS. IF SUCCESSFUL THE NEW APPROACH PROPOSED HERE COULD BE APPLIED TO SUBDUCTION ZONES AROUND THE WORLD LACKING IN THE KIND OF GPS COVERAGE WE HAVE IN THIS COUNTRY. ALL AROUND THE PACIFIC RING OF FIRE SUCH AS IN INDONESIA SOUTH AMERICA AND PARTS OF THE ALEUTIANS EXTREME EARTHQUAKE HAZARDS EXIST AND ARE MONITORED ONLY POORLY TODAY. DEVELOPMENT OF A RELIABLE SPACE-BASED TECHNIQUE COULD PROVIDE A TOOL FOR BETTER UNDERSTANDING OF THE HAZARD IN THESE AREAS.