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It has been assumed that Himalayan earthquakes are driven by the release of compressional strain accumulating close to the Greater Himalaya. However, elastic models of the Indo–Asian collision using recently imaged subsurface interface geometries suggest that a substantial fraction of the southernmost 500 kilometres of the Tibetan plateau participates in driving great ruptures. We show here that this Tibetan reservoir of elastic strain energy is drained in proportion to Himalayan rupture length, and that the consequent growth of slip and magnitude with rupture area, when compared to data from recent earthquakes, can be used to infer a ∼500-year renewal time for these events. The elastic models also illuminate two puzzling features of plate boundary seismicity: how great earthquakes can re-rupture regions that have already ruptured in recent smaller earthquakes and how mega-earthquakes with greater than 20 metres slip may occur at millennia-long intervals, driven by residual strain following many centuries of smaller earthquakes. Moving up in the world The Indian subcontinent is thrusting north into Asia at a rate of about 40 mm a year, sustaining the elevation of the Tibetan Plateau, deforming the Himalaya mountains and causing a string of earthquakes. Analysis of new and existing geodetic data suggests that the area of strain accumulation controlling great Himalayan earthquakes extends further into Tibet than was thought. The influence of southern Tibet may explain how mega-earthquakes can occur in regions recently ruptured by smaller earthquakes in terms of the build-up of residual strain.

The Superstition Hills Fault (SHF) exhibits a rich spectrum of slip modes, including M 6+ earthquakes, afterslip, quasi‐steady creep, and both triggered and spontaneous slow slip events (SSEs). Following 13 years of quiescence, creepmeters recorded 25 mm of slip during 16–19 May 2023. Additional sub‐events brought the total slip to 41 mm. The event nucleated on the northern SHF in early‐May and propagated bi‐laterally at rates on the order of kilometers per day. Surface offsets reveal a bi‐modal slip distribution, with slip on the northern section of the fault being less localized and lower amplitude compared to the southern section. Kinematic slip models confirm systematic variations in the slip distribution along‐strike and with depth and suggest that slip is largely confined to the shallow sedimentary layer. Observations and models of the 2023 SSE bear a strong similarity to previous slip episodes in 1999, 2006, and 2010, suggesting a characteristic behavior. Plain Language Summary Studying the mechanical properties and behavior of faults is essential for understanding earthquake ruptures. In this study, we investigate a recent slip event on the Superstition Hills Fault (SHF), which has a well‐documented record of slip. A notable aspect of the SHF is that it periodically undergoes “slow slip events” (SSEs), where the fault slips and releases energy without any accompanied ground shaking. During May‐July 2023, the SHF experienced a major SSE for the first time in 13 years. Our analysis shows that it was the largest documented SSE on the SHF and released equivalent energy to a magnitude 4.5 earthquake. We also find that the spatial pattern of fault slip is very similar to several previous slip events in 1999, 2006, and 2010, suggesting that the SHF has a tendency to slip in a characteristic manner. Key Points We document a recent spontaneous slow slip event (SSE) on the Superstition Hills Fault using creepmeter, Interferometric Synthetic Aperture Radar, Global Navigation Satellite System, and field measurements Over 41 mm of slip occurred from mid‐May to mid‐July 2023, with moment release corresponding to a Mw 4.5 earthquake The kinematics of the 2023 event are remarkably similar to several previous SSEs, suggesting a characteristic rupture process

Shallow creep events provide opportunities to understand the mechanical properties and behavior of faults. However, due to physical limitations observing creep events, the precise spatio‐temporal evolution of slip during creep events is not well understood. In 2023, the Superstition Hills and Imperial faults in California each experienced centimeter‐scale slip events that were captured in unprecedented detail by satellite radar, sub‐daily Global Navigation Satellite Systems, and creepmeters. In both cases, the slip propagated along the fault over 2–3 weeks. The Superstition Hills event propagated bilaterally away from its initiation point at average velocities of ∼9 km/day, but propagation velocities were locally much higher. The ruptures were consistent with slip from tens of meters to ∼2 km depths. These slowly propagating events reveal that the shallow crust of the Imperial Valley does not obey purely velocity‐strengthening or velocity‐weakening rate‐and‐state friction, but instead requires the consideration of fault heterogeneity or fault‐frictional behaviors such as dilatant strengthening. Plain Language Summary Faults that slip in a slow, aseismic process called creep present an opportunity to understand the frictional behavior of fault systems. In the spring of 2023, two fault systems in southern California experienced large slip events that were recorded in high resolution by ground‐based and space‐based measurements from GPS and satellite radar. The slip began spontaneously on both the Superstition Hills and Imperial faults and slowly propagated to other parts of each fault. The average slip propagation speed ranged from 0.4 to 9 km per day. Interestingly, this velocity is very similar to propagation velocities observed in subduction zones around the world and is approximately the speed of a sloth or a snail. Future work may help us understand what physical properties, such as confining stress, frictional strength, fluid pressure, and fluid diffusivity, control the propagation velocity of a slow slip event. Key Points The Superstition Hills and Imperial faults hosted centimeter‐scale transient slip events in spring 2023 Interferometric Synthetic Aperture Radar, high‐rate Global Navigation Satellite Systems, and local creepmeters characterized each slip event in space and time Slow slip propagated at 6–9 km/day along the Superstition Hills fault and 0.4 km/day along the Imperial fault, but locally faster or slower

Radar interferometry (InSAR), field measurements and creepmeters reveal surface slip on multiple faults in the Imperial Valley triggered by the main shock of the 4 April 2010 El Mayor‐Cucapah Mw 7.2 earthquake. Co‐seismic offsets occurred on the San Andreas, Superstition Hills, Imperial, Elmore Ranch, Wienert, Coyote Creek, Elsinore, Yuha, and several minor faults near the town of Ocotillo at the northern end of the mainshock rupture. We documented right‐lateral slip (<40 mm) on northwest‐striking faults and left‐lateral slip (<40 mm) on southwest‐striking faults. Slip occurred on 15‐km‐ and 20‐km‐long segments of the San Andreas Fault in the Mecca Hills (≤50 mm) and Durmid Hill (≤10 mm) respectively, and on 25 km of the Superstition Hills Fault (≤37 mm). Field measurements of slip on the Superstition Hills Fault agree with InSAR and creepmeter measurements to within a few millimeters. Dislocation models of the InSAR data from the Superstition Hills Fault confirm that creep in this sequence, as in previous slip events, is confined to shallow depths (<3 km).

Active faults release part of the elastic strain energy stored in the crust via aseismic slip, either through slow slip events (SSEs) or steady slowly creep. However, spatial and temporal interactions between these different styles of aseismic slip have yet to be quantified especially at depth. Along the central section of the North Anatolian Fault, we apply a Multichannel Singular Spectrum Analysis (MSSA) on GNSS time series of ground motion to detect a Mw ${M}_{w}$ 4.8 ± $\\pm $ 0.08 shallow SSE (2–5 km depth) lasting for 26 ± $\\pm $ 5 days, in agreement with local creepmeter observations. Our observations confirm the recurrence of SSEs next to a steadily creeping section of the fault. Finally, we discuss how steady creep and SSEs interact spatially and temporally along the fault segment.

Given that less-destructive earthquakes in the developing world have typically cost $3 billion-$10 billion11, earthquake-proof reconstruction in Haiti is likely to cost an order of magnitude more than has been promised so far, even using local materials and local manpower. Because construction projects are likely to offer employment opportunities for many Haitians in the coming decades, earthquake engineers1,13 have already articulated the importance of training contractors and labourers in sound construction methods.

Despite an overall sinistral slip rate of ≈3 cm/yr, few major earthquakes have occurred in the past 200 years along the Chaman fault system, the western boundary of the India Plate with the Eurasia Plate. GPS and InSAR data reported here indicate sinistral shear velocities of 8–17 mm/yr across the westernmost branches of the fault system, suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east. At its southernmost on‐land segment (≈26°N), near the triple junction between the Arabia, Eurasia, and India Plates, we find the velocity across the Ornach Nal fault is 15.1+13.4+16.9 mm/yr, with a locking depth probably less than 3 km. At latitude 30°N near the town of Chaman, Pakistan, where a M6.5 earthquake occurred in 1892, the velocity is 8.5+6.8+10.3mm/yr and the fault is locked at approximately 3.4 km depth. At latitude 33°N and further north, InSAR data indicate a velocity across the Chaman fault of 16.8 ± 2.7 mm/yr. The width of the plate boundary varies from several km in the south where we observe ≈2 mm/yr of convergence near the westernmost strike‐slip faults, to a few hundreds of km in the north where we observe 6–9 mm/yr of convergence, and where the faulting becomes distinctly transpressional. The shallow locking depth along much of the transform system suggests that earthquakes larger than those that have occurred in the historical record would be unexpected, and that the recurrence interval of those earthquakes that have occurred is of the order of one or two centuries, similar in length to the known historical record. Key Points Large strike‐slip earthquakes are uncommon on the Chaman fault Shallow interseismic locking depths are prevalent in the Chaman fault system

The enforcement of sound building practices would substantially reduce future fatalities from earthquakes in south central Asia. A quarter of the world's population inhabits the nations of Iran, Afghanistan, Pakistan, India, Nepal, Bhutan, Bangladesh, Sri Lanka, and Myanmar. These countries lie on or near the northern edge of the Arabian and Indian Plates that are colliding with the southern margin of the Eurasian Plate (see the figure, panel A) . The collision occurs mid-continent and, as a result, earthquakes have historically destroyed many settlements, especially in Iran ( 1 ). Deaths from earthquakes since 1900 have exceeded those in all previous centuries, and earthquake deaths to the east of Iran have far outnumbered those in Iran (see the figure, panel B). We ascribe this to the recently increased population at risk in Pakistan and India and to the fragility of construction methods introduced there in the past century.

Great Himalayan earthquakes are rare. Analysis of surface motions in the months after the 2015 Gorkha earthquake reveals negligible aseismic slip, implying that stress may be stored in the crust to be tapped during future great earthquakes. The magnitude 7.8 Gorkha earthquake in April 2015 ruptured a 150-km-long section of the Himalayan décollement terminating close to Kathmandu 1 , 2 , 3 , 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.