THE EARLY PHASES OF THE CRUSTAL DEFORMATION/EARTHQUAKE CYCLE FROM GNSS AND COMPLEMENTARY EARTH OBSERVATION DATASETS: IMPLICATIONS FOR EARTHQUAKE AND TSUNAMI HAZARDS RECENT EARTHQUAKES IN SUMATRA CHILE JAPAN AND NEPAL HAVE CAUSED SEVERE LOSS OF LIFE AND MASSIVE DAMAGE TO INFRASTRUCTURE. MITIGATION OF EARTHQUAKE AND TSUNAMI HAZARDS DEPENDS ON RELIABLE ESTIMATES OF THE PROBABILITY OF OCCURRENCE. GEODETICALLY THESE ESTIMATES ARE BASED ON EARTHQUAKE CYCLE MODELS THAT ARE CONSTRAINED BY GNSS- AND INSAR-DERIVED INTERSEISMIC VELOCITIES ACQUIRED IN QUIESCENT PERIODS TO DERIVE THE DEGREE OF PLATE COUPLING ASSUMING THAT THERE IS A CORRELATION BETWEEN COSEISMIC SLIP AND INTERSEISMIC COUPLING. RECENT THEORETICAL MODELS ATTEMPT TO EXPLAIN A WIDE RANGE OF OBSERVED FAULT BEHAVIOR FROM ASEISMIC CREEP TO MULTISEGMENT FINITE RUPTURES AND BEGIN TO QUESTION THE PREVIOUS SIMPLIFIED ASSUMPTIONS ON FAULT SEGMENTATION. WITH THE EXTENSIVE EARTH OBSERVATIONS CURRENTLY AVAILABLE INCLUDING HIGH RATE (0.1-1 S) GNSS WE PROPOSE INNOVATIVE WAYS TO TEST THESE NEW MODELS OF FAULT BEHAVIOR. MODELING OF THE DYNAMIC RUPTURE PROCESS INDICATES THAT ALONG-STRIKE VARIATIONS IN FAULT BEHAVIOR MAY BE INDICATING THE POTENTIAL FOR COSEISMIC WEAKENING TO OCCUR DEPENDING STRONGLY ON LOCAL SLIP AND SLIP RATE. RUPTURES CAN PROPAGATE BELOW THE SEISMOGENIC LAYER INTO THE DEEPER CREEPING LAYER CHANGING THE DEPTH DEPENDENCE OF FRICTIONAL AND HYDROLOGICAL PROPERTIES AND EVENTUALLY AFFECTING THE NUCLEATION CONDITIONS FOR FUTURE EARTHQUAKES. IN TESTING HYPOTHESES FOR THE EFFECT OF EARTHQUAKE RUPTURE ON DEPTH DEPENDENT FAULT PROPERTIES MODELS MUST SATISFY LONGER-TERM POSTSEISMIC OBSERVATIONS AS WELL AS CONSTRAINTS PROVIDED BY THE LOCATION AND DEPTH OF MICROSEISMICITY AND AFTERSHOCKS AS STRESS INDICATORS. THE HYPOTHESIS THAT COSEISMIC STRESS CHANGES MODIFY FAULT ZONE PROPERTIES AND CAN CHANGE THE BEHAVIOR NEAR THE BASE OF THE SEISMOGENIC ZONE FROM VELOCITY STRENGTHENING TO VELOCITY WEAKENING PREDICTS TIME DEPENDENT CHANGES IN DEFORMATION RESPONSE AT TIME SCALES RANGING FROM SECONDS TO DECADES. THE CHALLENGE IS TO BRIDGE THE GAP BETWEEN COSEISMIC AND POSTSEISMIC INVESTIGATIONS WHERE POSTSEISMIC STUDIES USUALLY DESCRIBE THE RESPONSE OF THE CRUST AND UPPER MANTLE USING DAILY DISPLACEMENT TIME SERIES OF ABOUT 30 DAYS OR LONGER. WE WILL EXPLOIT HIGHLY ACCURATE COSEISMIC AND POSTSEISMIC DEFORMATION ESTIMATES FROM HIGH-RATE GNSS AND COMPLEMENTARY EARTH OBSERVATIONS IN THE NEAR FIELD OF EARTHQUAKE RUPTURES THAT PUSHES THE FOCUS INTO THE SUBDAILY AND EVEN SUB-HOURLY TIME SCALES. EARTHQUAKE SLIP AND SLIP RATE ARE DERIVED OBSERVATIONALLY FROM KINEMATIC SLIP INVERSIONS WITH INCREASED RESOLUTION DUE TO THE AVAILABILITY OF COMPLEMENTARY EARTH OBSERVATIONS. TESTING THEORETICAL MODELS RELATING SLIP HISTORY TO FAULT PROPERTIES IS CRITICAL TO REVISING ESTIMATES OF POTENTIAL RUPTURE AREAS OF TSUNAMIGENIC EARTHQUAKES IN SUBDUCTION ZONES WORLDWIDE. WE HAVE DEVELOPED TECHNIQUES FOR DERIVING ENHANCED SLIP MODELS USING SEISMOGEODETIC (GNSS AND ACCELEROMETER) AND OTHER COMPLEMENTARY EARTH OBSERVATIONS (SEISMIC INSAR OFFSHORE WAVE MEASUREMENTS AND TIDE GAUGES DURING TSUNAMIGENESIS). OUR GROWING CATALOG OF HIGH-RATE GNSS DISPLACEMENTS AND EARTH OBSERVATIONS IN THE NEAR-SOURCE REGION FOR AN EXPANDING NUMBER OF SIGNIFICANT (M6-9) EARTHQUAKES FORESHOCKS AND AFTERSHOCKS HAVE ONLY BEGUN TO BE EXPLOITED FOR SYNOPTIC ASSESSMENT OF SEISMIC HAZARD EVOLUTION. WE WILL LINK THESE TO NEW OBSERVATIONS IN THE EARLY POSTSEISMIC PERIOD AND TO OUR HISTORICAL LONG-TERM DAILY DISPLACEMENT TIME SERIES ACCUMULATED OVER 25+ YEARS AND SPANNING SEVERAL PLATE BOUNDARIES. HERE WE PROPOSE TO IMPROVE OUR UNDERSTANDING OF THE UNDERLYING PHYSICS OF CRUSTAL DEFORMATION AND THE EARTHQUAKE CYCLE PARTICULARLY IN THE PERIOD OF EARLY ONSET POSTSEISMIC DEFORMATION AFTER THE DYNAMIC GROUND MOTIONS HAVE DISSIPATED. OUR PROPOSAL ADDRESSES THE FIRST CHALLENGE OF THE ESI STRATEGY IDENTIFIED IN LIVING ON A RESTLESS PLANET: WHA