ONE OF THE TOP SCIENCE QUESTIONS IN THE NASA DECADAL REPORT IS: HOW CAN LARGE-SCALE GEOLOGICAL HAZARDS BE ACCURATELY FORECAST IN A SOCIALLY RELEVANT TIMEFRAME? WE PROPOSE TO ADDRESS THIS QUESTION BY USING A COMBINATION OF INSAR AND GNSS TIME SERIES TO MEASURE TECTONIC CRUSTAL STRAIN RATE OVER THE ENTIRE SAN ANDREAS FAULT SYSTEM TO AN ACCURACY OF BETTER THAN 50 NANOSTRAIN/YR AT A SPATIAL RESOLUTION OF 10 KM. MOST DESTRUCTIVE EARTHQUAKES OCCUR IN REGIONS WHERE THE STRAIN RATE EXCEEDS THIS 50 NANOSTRAIN/YR THRESHOLD. THIS CORRESPONDS TO AN AVERAGE VELOCITY ACCURACY OF 0.5 MM/YR OVER THE 10 KM AVERAGING DISTANCE. THE EXISTING GNSS ARRAY ALONG THE SAN ANDREAS FAULT SYSTEM CAN PROVIDE THIS ACCURACY BUT ONLY AT A SPATIAL RESOLUTION OF 40 KM BECAUSE OF SPARSE COVERAGE. INSAR TIME SERIES DERIVED FROM 3 YEARS OF SENTINEL-1 DATA AT A 12-DAY CADENCE CAN ACHIEVE THIS SPATIAL RESOLUTION BUT SO FAR AT A MUCH LOWER ACCURACY OF 2-4 MM/YR. IMPROVING THE INSAR VELOCITY ACCURACY BY NEARLY ONE ORDER OF MAGNITUDE WILL REQUIRE AT LEAST 6 YEARS OF DATA COMBINED WITH A SIGNIFICANT IMPROVEMENT IN THE ACCURACY OF THE INSAR TIME SERIES. WE PROPOSE TO MOVE INSAR TIME SERIES FROM A LARGELY RELATIVE PHASE MEASUREMENT TO AN ABSOLUTE MEASUREMENT THAT CAN CONNECT THE PHASE FROM THE FIRST TO LAST SAR ACQUISITIONS IN THE STACK. THIS WILL INVOLVE APPLICATION OF THREE CORRECTIONS THAT ARE COMMONLY APPLIED TO GNSS DATA BUT NOT INSAR DATA. THE CORRECTIONS ARE SOLID EARTH/OCEAN LOADING TIDE IONOSPHERE DELAY AND RESOLVING THE 2PI INTEGER PHASE AMBIGUITY. IF SUCCESSFUL THESE CORRECTIONS WILL ENABLE THE 0.5 MM/YR ACCURACY THRESHOLD.