The magnitude 7.8 Gorkha earthquake in April 2015 ruptured a 150-km-long section of the Himalayan décollement terminating close to Kathmandu 1-4 . The earthquake failed to rupture the surface Himalayan frontal thrusts and raised concern that a future M w ≤ 7.3 earthquake could break the unruptured region to the south and west of Kathmandu. Here we use GPS records of surface motions to show that no aseismic slip occurred on the ruptured fault plane in the six months immediately following the earthquake. We find that although 70 mm of afterslip occurred locally north of the rupture, fewer than 25 mm of afterslip occurred in a narrow zone to the south. Rapid initial afterslip north of the rupture was largely complete in six months, releasing aseismic-moment equivalent to a M w 7.1 earthquake. Historical earthquakes in 1803, 1833, 1905 and 1947 also failed to rupture the Himalayan frontal faults, and were not followed by large earthquakes to their south. This implies that significant relict heterogeneous strain prevails throughout the Main Himalayan Thrust. The considerable slip during great Himalayan earthquakes may be due in part to great earthquakes tapping reservoirs of residual strain inherited from former partial ruptures of the Main Himalayan Thrust.The spatial distribution of surface deformation in the April M w 7.8 Nepal earthquake and its M w 7.3 aftershock ten days later was captured by several InSAR scenes and by continuously operating GPS receivers 1-8 . These data indicate that an average slip of 3.5 m occurred on a 60-km-wide × 150-km-long rupture of the northdipping décollement, the Main Himalayan Thrust (MHT), with maximum slip locally reaching 7 m approximately 15 km north of Kathmandu. Rupture propagated eastwards along the region of maximum interseismic strain near the Greater Himalaya, but terminated to the south near the Kathmandu valley (Fig. 1).The interseismic convergence rate in Nepal observed geodetically 9,10 is 18-20 mm yr −1 , similar to the rate of advance of the Himalaya over the Indian plate inferred from geological evidence 11 . The Indian plate descends beneath Tibet aseismically north of a seismically active transition zone in northern Nepal, south of which three decades of geodetic data indicate that the MHT is effectively locked 12 . The occasional rupture of this locked décollement accommodates the incremental northward passage of the Indian plate beneath the Himalaya. A several-thousand year record of this slip is emerging from the exhumation of surface ruptures of Himalayan frontal faults 13-15 (Main Frontal Thrust, MFT); however, the 2015 earthquake is one of several M ≤ 7.8Himalayan earthquakes whose southward rupture failed to rupture the MFT, and whose contribution to facilitating Himalayan moment release thereby eludes palaeoseismic investigation.InSAR data reveal that the 2015 earthquake did, however, trigger ∼5 cm of near-surface slip on a subsidiary branch of the frontal fault, the Main Dun Thrust (MDT), with no significant coseismic slip on the décollement between the...

We reevaluate the 72 year history of surface slip on the North Anatolian Fault at Ismetpasa since the Mw = 7.4 1944 Bolu/Gerede earthquake. A revised analysis of published observations suggests that days after the earthquake the fault had been offset by 3.7 m and 6 years later by an additional 0.74 m. Creep was first recognized on the fault in 1969 as a 0.13 m offset of a wall constructed in 1957 that now (2016) has been offset by 0.52 m. A carbon rod creep meter operated across the fault in the past 2 years confirms results from an invar wire creep meter operated 1982–1991 that surface slip is episodic. Months of fault inactivity are interrupted by slow slip (≤10 µm/d) or multiple creep events with cumulative amplitudes of 2–10 mm, durations of several weeks, and with slip rates briefly exceeding >2.5 mm/h. Creep events accommodate 80% of the surface slip and individually release ≈ 10−6 shear strain on the flanks of the uppermost 3–7 km of the fault. GPS and interferometric synthetic aperture radar methods yield a current fault slip rate of 7.6 ± 1 mm/yr suggesting that creep meters incompletely sample the full width of the surface shear zone. The slip rate has slowed from >10 mm/yr in 1969 to 6.1 mm/yr at present, 4.65 mm/yr of which appears to be due to steady interseismic creep driven by plate boundary stressing rates. We calculate that a further 1 m of aseismic surface slip will precede the next major earthquake on the fault assuming an ≈ 260 year main shock recurrence interval on this segment.