Showing papers on "Fault (geology) published in 2018"

Coseismic landslides triggered by the 8th August 2017 Ms 7.0 Jiuzhaigou earthquake (Sichuan, China): factors controlling their spatial distribution and implications for the seismogenic blind fault identification

Abstract: On 8th August 2017, a magnitude Ms 7.0 earthquake struck the County of Jiuzhaigou, in Sichuan Province, China. It was the third Ms ≥ 7.0 earthquake in the Longmenshan area in the last decade, after the 2008 Ms 8.0 Wenchuan earthquake and the 2013 Ms 7.0 Lushan earthquake. The event did not produce any evident surface rupture but triggered significant mass wasting. Based on a large set of pre- and post-earthquake high-resolution satellite images (SPOT-5, Gaofen-1 and Gaofen-2) as well as on 0.2-m-resolution UAV photographs, a polygon-based interpretation of the coseismic landslides was carried out. In total, 1883 landslides were identified, covering an area of 8.11 km2, with an estimated total volume in the order of 25–30 × 106 m3. The total landslide area was lower than that produced by other earthquakes of similar magnitude with strike-slip motion, possibly because of the limited surface rupture. The spatial distribution of the landslides was correlated statistically to a number of seismic, terrain and geological factors, to evaluate the landslide susceptibility at regional scale and to identify the most typical characteristics of the coseismic failures. The landslides, mainly small-scale rockfalls and rock/debris slides, occurred mostly along two NE-SW-oriented valleys near the epicentre. Comparatively, high landslide density was found at locations where the landform evolves from upper, broad valleys to lower, deep-cut gorges. The spatial distribution of the coseismic landslides did not seem correlated to the location of any known active faults. On the contrary, it revealed that a previously-unknown blind fault segment—which is possibly the north-western extension of the Huya fault—is the plausible seismogenic fault. This finding is consistent with what hypothesised on the basis of field observations and ground displacements.

Surface ruptures following the 30 October 2016 Mw 6.5 Norcia earthquake, central Italy

Abstract: We present a 1:25,000 scale map of the coseismic surface ruptures following the 30 October 2016 Mw 6.5 Norcia normal-faulting earthquake, central Italy. Detailed rupture mapping is based on almost 11,000 oblique photographs taken from helicopter flights, that has been verified and integrated with field data (>7000 measurements). Thanks to the common efforts of the Open EMERGEO Working Group (130 people, 25 research institutions and universities from Europe), we were able to document a complex surface faulting pattern with a dominant strike of N135°-160° (SW-dipping) and a subordinate strike of N320°-345° (NE-dipping) along about 28 km of the active Mt. Vettore–Mt. Bove fault system. Geometric and kinematic characteristics of the rupture were observed and recorded along closely spaced, parallel or subparallel, overlapping or step-like synthetic and antithetic fault splays of the activated fault systems, comprising a total surface rupture length of approximately 46 km when all ruptures were considered.

Earthquake nucleation and fault slip complexity in the lower crust of central Alaska

Abstract: Earthquakes start under conditions that are largely unknown. In laboratory analogue experiments and continuum models, earthquakes transition from slow-slipping, growing nucleation to fast-slipping rupture. In nature, earthquakes generally start abruptly, with no evidence for a nucleation process. Here we report evidence from a strike-slip fault zone in central Alaska of extended earthquake nucleation and of very-low-frequency earthquakes (VLFEs), a phenomenon previously reported only in subduction zone environments. In 2016, a VLFE transitioned into an earthquake of magnitude 3.7 and was preceded by a 12-hour-long accelerating foreshock sequence. Benefiting from 12 seismic stations deployed within 30 km of the epicentre, we identify coincident radiation of distinct high-frequency and low-frequency waves during 22 s of nucleation. The power-law temporal growth of the nucleation signal is quantitatively predicted by a model in which high-frequency waves are radiated from the vicinity of an expanding slow slip front. The observations reveal the continuity and complexity of slip processes near the bottom of the seismogenic zone of a strike-slip fault system in central Alaska.

Transpressional Rupture Cascade of the 2016 Mw 7.8 Kaikoura Earthquake, New Zealand

Abstract: Large earthquakes often do not occur on a simple planar fault but involve rupture of multiple geometrically complex faults. The 2016 M_w 7.8 Kaikoura earthquake, New Zealand, involved the rupture of at least 21 faults, propagating from southwest to northeast for about 180 km. Here we combine space geodesy and seismology techniques to study subsurface fault geometry, slip distribution, and the kinematics of the rupture. Our finite‐fault slip model indicates that the fault motion changes from predominantly right‐lateral slip near the epicenter to transpressional slip in the northeast with a maximum coseismic surface displacement of about 10 m near the intersection between the Kekerengu and Papatea faults. Teleseismic back projection imaging shows that rupture speed was overall slow (1.4 km/s) but faster on individual fault segments (approximately 2 km/s) and that the conjugate, oblique‐reverse, north striking faults released the largest high‐frequency energy. We show that the linking Conway‐Charwell faults aided in propagation of rupture across the step over from the Humps fault zone to the Hope fault. Fault slip cascaded along the Jordan Thrust, Kekerengu, and Needles faults, causing stress perturbations that activated two major conjugate faults, the Hundalee and Papatea faults. Our results shed important light on the study of earthquakes and seismic hazard evaluation in geometrically complex fault systems.

The M7 2016 Kumamoto, Japan, Earthquake: 3-D Deformation Along the Fault and Within the Damage Zone Constrained From Differential Lidar Topography

Abstract: Three-dimensional near-fault coseismic deformation fields from high-resolution differential topography provide new information on the behavior of the shallow fault zone in large surface-rupturing earthquakes. Our work focuses on the 16 April 2016 Mw 7.0 Kumamoto, Japan, earthquake, which ruptured ~40 km of the Futagawa-Hinagu Fault Zone on Kyushu Island with an oblique strike-slip mechanism and surface offset exceeding 2 m. Our differential lidar analysis constrains the structural style of strain accommodation along the primary fault trace and the surrounding damage zone. We show that 36 ± 29% and 62 ± 32% of the horizontal and vertical deformation, respectively, was accommodated off the principal fault trace. The horizontal strains of up to 0.03 suggest that the approximate elastic strain limit was exceeded over a ~250 m width in many locations along the rupture. The inelastic deformation of the fault volume produced the observed distributed deformation at the Earth’s surface. We demonstrate a novel approach for calculating 3-D displacement uncertainties, indicating errors of centimeters to a few decimeters for displacements computed over 50 m horizontal windows. Errors correlate with land cover and relief, with flatter agricultural land associated with the highest displacement uncertainty. These advances provide a framework for future analyses of shallow earthquake behavior using differential topography.

Earthquake damage patterns resolve complex rupture processes

Abstract: Large continental earthquakes activate multiple faults in a complex fault system, dynamically inducing co-seismic damage around them. The 2016 Mw 7.8 Kaikoura earthquake in the northern South Island of New Zealand has been reported as one of the most complex continental earthquakes ever documented1, which resulted in a distinctive on and off-fault deformation pattern. Previous geophysical studies confirm that the rupture globally propagated northward from epicenter. However, the exact rupture- propagation path is still not well understood because of the geometrical complexity, partly at sea, and the possibility of a blind thrust. Here we use a combination of state-of- the-art observation of surface deformation, provided by optical image correlation, and first principle physics-based numerical modeling to determine the most likely rupture path. We quantify in detail the observed horizontal co-seismic deformation and identify specific off-fault damage zones in the area of the triple junction between the Jordan, the Kekerengu and the Papatea fault segments. We also model dynamic rupture propagation, including the activation of off-fault damage, for two alternative rupture scenarios through the fault triple junction. Comparing our observations with the results from the above two modeled scenarios we show that only one of the scenarios best explains both the on and off-fault deformation fields. Our results provide a unique insight into the rupture pathway, by observing, and modeling, both on and off-fault deformation. We propose this combined approach here to narrow down the possible rupture scenarios for large continental earthquakes accompanied by co-seismic off-fault damage.

Tectono-sedimentary evolution of the Plio-Pleistocene Corinth rift, Greece

Abstract: The onshore central Corinth rift contains a syn-rift succession >3 km thick deposited in 5–15 km-wide tilt blocks, all now inactive, uplifted and deeply incised. This part of the rift records upward deepening from fluviatile to lake-margin conditions and finally to sub-lacustrine turbidite channel and lobe complexes, and deep-water lacustrine conditions (Lake Corinth) were established over most of the rift by 3.6 Ma. This succession represents the first of two phases of rift development – Rift 1 from 5.0–3.6 to 2.2–1.8 Ma and Rift 2 from 2.2–1.8 Ma to present. Rift 1 developed as a 30 km-wide zone of distributed normal faulting. The lake was fed by four major N- to NE-flowing antecedent drainages along the southern rift flank. These sourced an axial fluvial system, Gilbert fan deltas and deep lacustrine turbidite channel and lobe complexes. The onset of Rift 2 and abandonment of Rift 1 involved a 30 km northward shift in the locus of rifting. In the west, giant Gilbert deltas built into a deepening lake depocentre in the hanging wall of the newly developing southern border fault system. Footwall and regional uplift progressively destroyed Lake Corinth in the central and eastern parts of the rift, producing a staircase of deltaic and, following drainage reversal, shallow marine terraces descending from >1000 m to present-day sea level. The growth, linkage and death of normal faults during the two phases of rifting is interpreted to reflect self-organisation and strain localisation along co-linear border faults. In the west, interaction with the Patras rift occurred along the major Patras dextral strike-slip fault. This led to enhanced migration of fault activity, uplift and incision of some early Rift 2 fan deltas, and opening of the Rion Straits at c. 400–600 ka. The landscape and stratigraphic evolution of the rift was strongly influenced by regional palaeotopographic variations and local antecedent drainage, both inherited from the Hellenide fold and thrust belt. This article is protected by copyright. All rights reserved.

Earthquake Damage Patterns Resolve Complex Rupture Processes

Abstract: Fracture damage patterns around faults, induced by dynamic earthquake rupture, is an invaluable record to clarify the rupture process on complex fault networks. The 2016 M w 7.8 Kaikoura earthquake in New Zealand has been reported as one of the most complex earthquakes ever documented that ruptured at-least 15 faults. High-resolution optical satellite image correlation provides distinctive profiles of displacement field around the faults, and helps visualize the off-fault damage pattern. This observational approach, coupled with a first-of-its-kind numerical tool that captures rupture and activation of off-fault damage, allowed the determination of the most likely rupture scenario. This study demonstrates that complex rupture process can be explained in a rather simple way via a synergetic combination of state-of-the-art observation and first principle physics-based numerical modeling of off-fault damage. One Sentence Summary: Distinct fracture deformation patterns around faults resolves complex earthquake rupture scenario

The role of pre-existing structures during rifting, continental breakup and transform system development, offshore West Greenland

Abstract: Continental breakup between Greenland and North America produced the small oceanic basins of the Labrador Sea and Baffin Bay, which are connected via the Davis Strait, a region mostly comprised of continental crust. This study contributes to the debate regarding the role of pre-existing structures on rift development in this region using seismic reflection data from the Davis Strait data to produce a series of seismic surfaces, isochrons and a new offshore fault map from which three normal fault sets were identified as (i) NE-SW, (ii) NNW-SSE and (iii) NW-SE. These results were then integrated with plate reconstructions and onshore structural data allowing us to build a two-stage conceptual model for the offshore fault evolution in which basin formation was primarily controlled by rejuvenation of various types of pre-existing structures. During the first phase of rifting between at least Chron 27 (ca. 62 Ma; Palaeocene), but potentially earlier, and Chron 24 (ca. 54 Ma; Eocene) faulting was primarily controlled by pre-existing structures with oblique normal reactivation of both the NE-SW and NW-SE structural sets in addition to possible normal reactivation of the NNW-SSE structural set. In the second rifting stage between Chron 24 (ca. 54 Ma; Eocene) and Chron 13 (ca. 35 Ma; Oligocene), the sinistral Ungava transform fault system developed due to the lateral offset between the Labrador Sea and Baffin Bay. This lateral offset was established in the first rift stage possibly due to the presence of the Nagssugtoqidian and Torngat terranes being less susceptible to rift propagation. Without the influence of pre-existing structures the manifestation of deformation cannot be easily explained during either of the rifting phases. Although basement control diminished into the post-rift, the syn-rift basins from both rift stages continued to influence the location of sedimentation possibly due to differential compaction effects. Variable lithospheric strength through the rifting cycle may provide an explanation for the observed diminishing role of basement structures through time.

Subduction and retreating of the western Pacific plate resulted in lithospheric mantle replacement and coupled basin-mountain respond in the North China Craton

Abstract: The North China Craton (NCC) witnessed Mesozoic vigorous tectono-thermal activities and transition in the nature of deep lithosphere. These processes took place in three periods: (1) Late Paleozoic to Early Jurassic (~170 Ma); (2) Middle Jurassic to Early Cretaceous (160–140 Ma); (3) Early Cretaceous to Cenozoic (140 Ma to present). The last two stages saw the lithospheric mantle replacement and coupled basin-mountain response within the North China Craton due to subduction and retreating of the Paleo-Pacific plate, and is the emphasis in this paper. In the first period, the subduction and closure of the Paleo-Asian Ocean triggered the back-arc extension, syn-collisional compression and then post-collisional extension accompanied by ubiquitous magmatism along the northern margin of the NCC. Similar processes happened in the southern margin of the craton as the subduction of the Paleo-Tethys ocean and collision with the South China Block. These processes had caused the chemical modification and mechanical destruction of the cratonic margins. The margins could serve as conduits for the asthenosphere upwelling and had the priority for magmatism and deformation. The second period saw the closure of the Mongol-Okhotsk ocean and the shear deformation and magmatism induced by the drifting of the Paleo-Pacific slab. The former led to two pulse of N-S trending compression (Episodes A and B of the Yanshan Movement) and thus the pre-existing continental marginal basins were disintegrated into sporadically basin and range province by the Mesozoic magmatic plutons and NE-SW trending faults. With the anticlockwise rotation of the Paleo-Pacific moving direction, the subduction-related magmatism migrated into the inner part of the craton and the Tanlu fault became normal fault from a sinistral one. The NCC thus turned into a back-arc extension setting at the end of this period. In the third period, the refractory subcontinental lithospheric mantle (SCLM) was firstly remarkably eroded and thinned by the subduction-induced asthenospheric upwelling, especially those beneath the weak zones (i.e., cratonic margins and the lithospheric Tanlu fault zone). Then a slightly lithospheric thickening occurred when the upwelled asthenosphere got cool and transformed to be lithospheric mantle accreted (~125 Ma) beneath the thinned SCLM. Besides, the magmatism continuously moved southeastward and the extensional deformations preferentially developed in weak zones, which include the Early Cenozoic normal fault transformed from the Jurassic thrust in the Trans-North Orogenic Belt, the crustal detachment and the subsidence of Bohai basin caused by the continuous normal strike slip of the Tanlu fault, the Cenozoic graben basins originated from the fault depression in the Trans-North Orogenic Belt, the Bohai Basin and the Sulu Orogenic belt. With small block size, inner lithospheric weak zones and the surrounding subductions/collisions, the Mesozoic NCC was characterized by (1) lithospheric thinning and crustal detachment triggered by the subduction-induced asthenospheric upwelling. Local crustal contraction and orogenesis appeared in the Trans-North Orogenic Belt coupled with the crustal detachment; (2) then upwelled asthenosphere got cool to be newly-accreted lithospheric mantle and crustal grabens and basin subsidence happened, as a result of the subduction zone retreating. Therefore, the subduction and retreating of the western Pacific plate is the outside dynamics which resulted in mantle replacement and coupled basin-mountain respond within the North China Craton. We consider that the Mesozoic decratonization of the North China Craton, or the Yanshan Movement, is a comprehensive consequence of complex geological processes proceeding surrounding and within craton, involving both the deep lithospheric mantle and shallow continental crust.

Active Deformation of Malawi Rift's North Basin Hinge Zone Modulated by Reactivation of Preexisting Precambrian Shear Zone Fabric

Abstract: Key Points: 1. Filtered aeromagnetic data elucidates the relationship between earthquake surface ruptures and buried faults along the North Basin hinge-zone, Malawi Rift. 2. Fault segments align with basement shear zone fabric. 3. Strain accommodation in the North Basin hinge zone is modulated by reactivation of the underlying Precambrian shear zone fabric. Abstract: We integrated temporal aeromagnetic data and recent earthquake data to address the long-standing question on the role of pre-existing Precambrian structures in modulating strain accommodation and subsequent ruptures leading to seismic events within the East African Rift System (EARS). We used aeromagnetic data to elucidate the relationship between the locations of the 2009 Mw 6.0 Karonga, Malawi earthquake surface ruptures and buried basement faults along the hinge zone of the half-graben comprising the North Basin of the Malawi Rift. Through the application of derivative filters and depth-to-magnetic-source modeling, we identified and constrained the trend of the Precambrian metamorphic fabrics and correlated them to the three-dimensional (3D) structure of buried basement faults. Our results reveal an unprecedented detail of the basement fabric dominated by high frequency WNW- to NW-trending magnetic lineaments associated with the Precambrian Mughese Shear Zone fabric. The high frequency magnetic lineaments are superimposed by lower frequency NNW-trending magnetic lineaments associated with possible Cenozoic faults. Surface ruptures associated with the 2009 Mw 6.0 Karonga earthquake swarm aligned with one of the NNW-trending magnetic lineaments defining a normal fault that is characterized by right-stepping segments along its northern half and coalesced segments on its southern half. Fault geometries, regional kinematics and spatial distribution of seismicity suggest that seismogenic faults reactivated the basement fabric found along the half-graben hinge zone. We suggest that focusing of strain accommodation and seismicity along the half-graben hinge zone is facilitated and modulated by the presence of the basement fabric.

FinDer v.2: Improved real-time ground-motion predictions for M2–M9 with seismic finite-source characterization

Abstract: Recent studies suggest that small and large earthquakes nucleate similarly, and that they often have indistinguishable seismic waveform onsets. The characterization of earthquakes in real time, such as for earthquake early warning, therefore requires a flexible modeling approach that allows a small earthquake to become large as fault rupture evolves over time. Here, we present a modeling approach that generates a set of output parameters and uncertainty estimates that are consistent with both small/moderate (≤M6.5) and large earthquakes (>M6.5) as is required for a robust parameter interpretation and shaking forecast. Our approach treats earthquakes over the entire range of magnitudes (>M2) as finite line-source ruptures, with the dimensions of small earthquakes being very small (<100 m) and those of large earthquakes exceeding several tens to hundreds of kilometres in length. The extent of the assumed line source is estimated from the level and distribution of high-frequency peak acceleration amplitudes observed in a local seismic network. High-frequency motions are well suited for this approach, because they are mainly controlled by the distance to the rupturing fault. Observed ground-motion patterns are compared with theoretical templates modeled from empirical ground-motion prediction equations to determine the best line source and uncertainties. Our algorithm extends earlier work by Bose et al. for large finite-fault ruptures. This paper gives a detailed summary of the new algorithm and its offline performance for the 2016 M7.0 Kumamoto, Japan and 2014 M6.0 South Napa, California earthquakes, as well as its performance for about 100 real-time detected local earthquakes (2.2 ≤ M ≤ 5.1) in California. For most events, both the rupture length and the strike are well constrained within a few seconds (<10 s) of the event origin. In large earthquakes, this could allow for providing warnings of up to several tens of seconds. The algorithm could also be useful for resolving fault plane ambiguities of focal mechanisms and identification of rupturing faults for earthquakes as small as M2.5.

Geologic Inheritance and Earthquake Rupture Processes: The 1905 M ≥ 8 Tsetserleg-Bulnay Strike-Slip Earthquake Sequence, Mongolia

Abstract: In 1905, 14 days apart, two M ~ 8 continental strike‐slip earthquakes, the Tsetserleg and Bulnay earthquakes, occurred on the Bulnay fault system, in Mongolia. Together, they ruptured four individual faults, with a total length of ~676 km. Using submetric optical satellite images “Pleiades” with ground resolution of 0.5 m, complemented by field observation, we mapped in detail the entire surface rupture associated with this earthquake sequence. Surface rupture along the main Bulnay fault is ~388 km in length, striking nearly E‐W. The rupture is formed by a series of fault segments that are 29 km long on average, separated by geometric discontinuities. Although there is a difference of about 2 m in the average slip between the western and eastern parts of the Bulnay rupture, along‐fault slip variations are overall limited, resulting in a smooth slip distribution, except for local slip deficit at segment boundaries. We show that damage, including short branches and secondary faulting, associated with the rupture propagation, occurred significantly more often along the western part of the Bulnay rupture, while the eastern part of the rupture appears more localized and thus possibly structurally simpler. Eventually, the difference of slip between the western and eastern parts of the rupture is attributed to this difference of rupture localization, associated at first order with a lateral change in the local geology. Damage associated to rupture branching appears to be located asymmetrically along the extensional side of the strike‐slip rupture and shows a strong dependence on structural geologic inheritance.

Chilean megathrust earthquake recurrence linked to frictional contrast at depth

Abstract: Fundamental processes of the seismic cycle in subduction zones, including those controlling the recurrence and size of great earthquakes, are still poorly understood. Here, by studying the 2016 earthquake in southern Chile—the first large event within the rupture zone of the 1960 earthquake (moment magnitude (Mw) = 9.5)—we show that the frictional zonation of the plate interface fault at depth mechanically controls the timing of more frequent, moderate-size deep events (Mw 8.5). We model the evolution of stress build-up for a seismogenic zone with heterogeneous friction to examine the link between the 2016 and 1960 earthquakes. Our results suggest that the deeper segments of the seismogenic megathrust are weaker and interseismically loaded by a more strongly coupled, shallower asperity. Deeper segments fail earlier (~60 yr recurrence), producing moderate-size events that precede the failure of the shallower region, which fails in a great earthquake (recurrence >110 yr). We interpret the contrasting frictional strength and lag time between deeper and shallower earthquakes to be controlled by variations in pore fluid pressure. Our integrated analysis strengthens understanding of the mechanics and timing of great megathrust earthquakes, and therefore could aid in the seismic hazard assessment of other subduction zones. The recurrence time of megathrust earthquakes in Chile may be controlled by frictional contrasts at depth, according to analyses of stress build-up and release related to the December 2016 southern Chile earthquake.

Faults and associated karst collapse suggest conduits for fluid flow that influence hydraulic fracturing-induced seismicity.

Abstract: During December 2011, a swarm of moderate-magnitude earthquakes was induced by hydraulic fracturing (HF) near Cardston, Alberta. Despite seismological associations linking these two processes, the hydrological and tectonic mechanisms involved remain unclear. In this study, we interpret a 3D reflection-seismic survey to delve into the geological factors related to these earthquakes. First, we document a basement-rooted fault on which the earthquake rupture occurred that extends above the targeted reservoir. Second, at the reservoir's stratigraphic level, anomalous subcircular features are recognized along the fault and are interpreted as resulting from fault-associated karst processes. These observations have implications for HF-induced seismicity, as they suggest hydraulic communication over a large (vertical) distance, reconciling the discrepancy between the culprit well trajectory and earthquake hypocenters. We speculate on how these newly identified geological factors could drive the sporadic appearance of induced seismicity and thus be utilized to avoid earthquake hazards.

Episodic creep events on the San Andreas Fault caused by pore-pressure variations.

Abstract: Recent seismic and geodetic observations indicate that interseismic creep rate varies in both time and space. The spatial extent of creep pinpoints locked asperities, while its temporary accelerations, known as slow-slip events, may trigger earthquakes. Although the conditions promoting fault creep are well-studied, the mechanisms for initiating episodic slow-slip events are enigmatic. Here we investigate surface deformation measured by radar interferometry along the central San Andreas Fault between 2003 and 2010 to constrain the temporal evolution of creep. We show that slow-slip events are ensembles of localized creep bursts that aseismically rupture isolated fault compartments. Using a rate-and-state friction model, we show that effective normal stress is temporally variable on the fault, and support this using seismic observations. We propose that compaction-driven elevated pore fluid pressure in the hydraulically isolated fault zone and subsequent frictional dilation cause the observed slow-slip episodes. We further suggest that the 2004 Mw 6 Parkfield earthquake might have been triggered by a slow-slip event, which increased the Coulomb failure stress by up to 0.45 bar per year. This implies that while creeping segments are suggested to act as seismic rupture barriers, slow-slip events on these zones might promote seismicity on adjacent locked segments.

Cenozoic tectonic subsidence in the Qiongdongnan Basin, northern South China Sea

Abstract: A number of major controversies exist in the South China Sea, including the timing and pattern of seafloor spreading, the anomalous alternating strike-slip movement on the Red River Fault, the existence of anomalous post-rift subsidence and how major submarine canyons have developed. The Qiongdongnan Basin is located in the intersection of the northern South China Sea margin and the strike-slip Red River fault zone. Analysing the subsidence of the Qiongdongnan Basin is critical in understanding these controversies. The basin-wide unloaded tectonic subsidence is computed through 1D backstripping constrained by the reconstruction of paleo-water depths and the interpretation of dense seismic profiles and wells. Results show that discrete subsidence sags began to form in the central depression during the middle and late Eocene (45-31.5 Ma). Subsequently in the Oligocene (31.5-23 Ma), more faults with intense activity formed, leading to rapid extension with high subsidence (40-90 m/myr). This extension is also inferred to be affected by the sinistral movement of the offshore Red River Fault as new subsidence sags progressively formed adjacent to this structure. Evidence from faults, subsidence, magmatic intrusions and strata erosion suggest that the breakup unconformity formed at ~23 Ma, coeval with the initial seafloor spreading in the south-western sub-basin of the South China Sea, demonstrating the breakup unconformity in the Qiongdongnan Basin is younger than that observed in the Pearl River Mouth Basin (~32-28 Ma) and Taiwan region (~39-33 Ma), which implies that the seafloor spreading in the South China Sea began diachronously from east to west. The post-rift subsidence was extremely slow during the early and middle Miocene (16 m/myr, 23-11.6 Ma), probably caused by the transient dynamic support induced by mantle convection during seafloor spreading. Subsequently, rapid post-rift subsidence occurred during the late Miocene (144 m/myr, 11.6-5.5 Ma) possibly as the dynamic support disappeared. The post-rift subsidence slowed again from the Pliocene to the Quaternary (24 m/myr, 5.5-0 Ma), but a subsidence centre formed in the west with the maximum subsidence of ~450 m, which coincided with a basin with the sediment thickness exceeding 5500 m and is inferred to be caused by sediment-induced ductile crust flow. Anomalous post-rift subsidence in the Qiongdongnan Basin increased from ~300 m in the northwest to ~1200 m in the southeast, and the post-rift vertical movement of the basement was probably the most important factor to facilitate the development of the central submarine canyon. This article is protected by copyright. All rights reserved.