Tan-Lu Fault Research Articles

Strong historical earthquakes and their relationships with the Tan-Lu fault system and modern seismicity in eastern China

The largest earthquake (Ms 8½) in eastern China occurred near Tancheng in 1668. Six M ≥ 6 earthquakes occurred in this region in historical time. We re-examine the primary historical archives from this region, adding independent constraints such as maps of active faults, local topography, intensity attenuation laws for China, and relevant administrative practices in archiving data, to reassess source parameters (epicenter, magnitude, or maximum intensity). We use the seismic density index—a measure of the clustering of seismicity weighted by source magnitude—to identify candidate zones of present-day clustering of seismicity than may represent a long-term memory of past historical events in an intraplate setting. We update at least one of the source parameters for four of the seven events. The main shock and two aftershocks of the 1668–1672 Ms 8½ Tancheng earthquake sequence locate along the strike of the Tan-Lu fault zone, each associated with significant and contiguous seismic density anomalies whose elliptical contours are elongated along its strike. A third major aftershock (Ms ≈ 6) in this sequence locates some 200 km away from the fault zone. Six of the seven historical events have seismic density anomalies that cannot be explained by aftershocks of modern seismicity (ML ≤ 5.3), and hence are candidate zones for long-lived aftershock sequences. In contrast, there are no significant seismic density anomalies along the section of Tan-Lu fault south of Suqian, despite palaeo-seismic evidence for a Ms 8½ earthquake around 6280 B.C., providing an upper bound to long-term memory of great earthquakes in this region.

High-resolution crustal and upper mantle shear-wave velocity structure beneath the central-southern Tanlu fault: Implications for its initiation and evolution

The Tanlu fault is a well-known lithosphere-cutting, strike-slip fault in eastern China and it has played an important role in regional plate tectonics since the middle Mesozoic. However, the initiation mechanisms and tectonic evolution of the Tanlu fault remain controversial, in part due to the absence of constraints from deep structures. In this study, we inverted 5–150 s surface-wave dispersion data collected from 253 permanent stations and 111 temporary stations in the vicinity of the central-southern Tanlu fault and obtained both isotropic and azimuthally anisotropic shear-wave velocity (Vs) models in the crust and upper mantle simultaneously. The new Vs models reveal unprecedented multiple patterns of anomalies. There is, for example, an arc-shaped pattern of fast directions found in the South China plate (SCP), providing direct evidence of the sudden termination of the Tanlu fault at its southern end; orogen-parallel fast directions and high-velocity anomalies were detected beneath the Dabie and Sulu orogens, which are believed to be the residue of the delaminated lithosphere. Based on the evidence collected, we propose a four-stage tectonic model for the Tanlu fault. The tectonic model suggests that the area has been subjected to multiple geologic processes since the Early Mesozoic, including oceanic-continental collision, continental-continental collision, break-off of oceanic slabs, lithospheric delamination, and convective erosion resulting from corner flow. As such, the proposed tectonic model reconciles the newly discovered Vs anomalies as well as various previous findings, providing profound insight into regional deformations and the evolution of the Tanlu fault and its adjacent areas.

Detailed shallow structure of the seismogenic fault of the 1976 Ms7.8 Tangshan earthquake, China

In 1976, an Ms7.8 strong earthquake occurred in the Tangshan region of Northeast China within an ancient craton. In this study, we conducted shallow seismic exploration, drilling-based exploration, and exploratory trench excavation of ground fissures in the Tangshan Fault Zone and obtained a high-resolution shallow seismic profile. Through analysis of its lithology and sedimentary cycle, we constructed a composite drilling profile across the faults. Coupled with the shallow fault combination patterns identified from the exploratory trenches, the profile reveals that the Guye-Nanhu Fault was the shallow response fault in the seismogenic structure of the Tangshan earthquake. This fault is a strike-slip fault with a positive flower structure; the reverse fault branches become progressively steeper with depth and converge downward toward the vertical main strike-slip fault. A high-angle thrust fault is located to the west of the main strike-slip fault, and a series of small-scale normal faults appear in front of this fault, owing to local extension. The tectonic form revealed by the deep seismic reflection profiles further supports the superficial tectonic model. The near-NEE orientation of the stress field in North China and the lower strike-slip movement component of the Tanlu Fault Zone facilitate faulting in the Tangshan–Hejian–Xingtai Fault Zone, which lies diagonally in the middle rectangular area of the North China Plain faulted basin. The detailed structural model of the seismogenic fault obtained by various detection methods is of great significance for understanding the seismogenic mechanism of the Tangshan earthquake.

Cenozoic tectonic evolution of the Bohai Bay Basin: Constraints from strike-slip activities of the Wangjiagang fault zone, NE China

The Wangjiagang (WJG) fault zone is regarded as the northward propagation of the Tan-Lu fault zone (TLFZ) in the Bohai Bay Basin (BBB). We used three-dimensional seismic and borehole data, as well as structure and isopach maps, to describe the structural properties and tectonic development of the WJG fault zone. The properties and thickness of the mechanical layer are the principal factors of differences in the deformation of the strike-slip fault zone. Extensional tectonics and strike-slip faulting occurred in WJG. Not only does strike-slip faulting regulate sand body distribution, but it also plays a critical role in oil migration. WJG provides a record of the tectonic evolution of the BBB and how it responded to plate interactions around the Pacific-Eurasian-Indian plates and/or the strike-slip faulting of the TLFZ. The BBB extended in the early Paleocene as a result of relative relaxation between the Pacific and Eurasian plates and the upwelling of the asthenosphere mantle. Before and after the late Eocene (ca. 42 Ma), the tectonic stress regimes at a nearly N-S-oriented extensional to dextral strike-slip faulting along TLFZ coincided with the strike-slip faulting of the pre-existing fault in WJG. The Pacific Plate's change in direction and rate of subduction, as well as the far-field effect of a hard collision between the Indian and Eurasian plates, caused the TLFZ's two walls to move in opposite directions. The resulting force couple caused a strong simple shear in the TLFZ and adjacent areas, including the WJG fault zone.

Late Quaternary sedimentation and neotectonics in Liaodong Bay, northern Bohai Sea

The Bohai Sea is a typical shelf sea, with obvious sediment differences in different regions. Although Liaodong Bay is the largest bay in the Bohai Sea, there lacks boreholes with precise dating. In this paper, the core sediments taken from YKC-2 borehole in the northeastern of Liaodong Bay are dated with AMS14C and OSL, in addition to grain size analysis, foraminifera and pollen identification, lithological characteristics and other testing results. Correlation is made with the global sea level change curve, and upon the basis the evolution of paleoenvironment in the northeast of Liaodong Bay is reconstructed. It is speculated that the age of the bottom of borehole YKC-2 is 150 kyr B.P., and two transgressions have been recorded, similar to the situation in JXC-1, a borehole 46.7 km to the west. It can be found that the sedimentation rate of YKC-2 borehole is obviously higher than that of JXC-1. The authors’ research found that it is mainly controlled by two factors: the provenance difference and the differential movement of basin controlling faults. In the west, sediments are mainly transported by the Bohai Sea current, with insufficient sediment supply, and the basin-controlling faults are rather stable and very weak in activity. In the east, sediments are transported mainly by the surrounding rivers with sufficient sediment supply; and the changes in accommodation space are under the control of the Tan-Lu fault zone. Affected by the strong extensional dynamic environment of the Bohai Bay Basin, the accommodation space, where the borehole YKC-2 is located, continuously increased for deposition of near-source river sediments. This article is an endeavor to study the evolution of the Late Quaternary sedimentary environment and the influence of tectonic activity on Quaternary sedimentation in the Bohai Sea.

Comparative Study of Tectonic Evolution and Oil–Gas Accumulation in the Ri-Qing-Wei Basin and the Jiaolai Basin

The Ri-Qing-Wei basin is located in the central Sulu Orogeny on the eastern side of the Tanlu fault zone in eastern Shandong province. To the north, the Jiaonan uplift separates it from the Jiaolai basin, where drilling in the lower Cretaceous sedimentary rock of the Laiyang group has indicated good oil and gas reserves. Drilling in the Ri-Qing-Wei basin, in contrast, is in the preliminary exploration stage. Lingke 1, the only scientific well, is on Lingshan Island on the basin boundary, and it encountered a large set of source rocks 700 m thick. The two basins were comprehensively compared and analyzed based on comprehensive fieldwork, drilling, core data, seismic profiling, sedimentary filling sequence, tectonic evolution history, basin burial history, geothermal history, and geochemical characteristics of the source rocks. The results showed three things: (1) from the late Jurassic to the early Cretaceous (the Laiyang period), subduction of the paleo-Pacific plate under the Eurasian plate delaminated the lithospheric mantle of the Sulu Orogeny, thus forming a series of passive continental rift basins. Of these, the Ri-Qing-Wei is central and the Jiaolai is its branch. After the active rift stage in the Qingshan period and the depression stage in the Wangshi period, the burial depth of the source rocks in the Ri-Qing-Wei basin was up to 6000 m, while the maximum burial depth in the Jiaolai basin was about 3000 m. The paleogeotemperature of both basins exceeded 125 °C, indicating that the source rocks were very mature. (2) A comprehensive comparison of their geochemical characteristics—organic matter abundance, type, and maturity—showed that both basins have oil-generating potential. It is worth noting that the magmatic activity in the Qingshan period had a positive effect on the evolution of the source rocks but was not the key factor: burial depth was. (3) Oil and gas failed to accumulate in the Jiaolai basin because they were destroyed by the lateral tectonic activities. During the right-lateral strike-slip stage (50 ± 5 Ma) during the late Wangshi, the Jiaolai basin was strongly uplifted over a range of more than 1000 m by the Tanlu and Wulian-Mouji fault zones along the boundary. The Wangshi group, as a cap rock, was eroded, and oil and gas overflowed along the fault that reached the surface. The late Wangshi period uplift of the Ri-Qing-Wei basin was less than 1000 m because the source rock was deeper, and the reverse faults in the basin were sealed well. The uplift did little damage to the oil in the Ri-Qing-Wei basin. Above all, tectonic evolution was the main controlling factor of oil accumulation in the study area, and the layers of the Laiyang group in the Ri-Qing-Wei basin have oil and gas potential, making it a prospective target for unconventional offshore oil and gas exploration.

Earth's one‐of‐a‐kind fault: The Tanlu fault

AbstractLarge‐scale strike‐slip faulting commonly occurs in active tectonic margins, but rarely, if ever, do large faults cut deep into ancient continental nuclei known as cratons. With thick mantle roots, cratons are considered to be the most tectonically stable portions of Earth's continental lithosphere, with an eminent exception being the relatively recent destruction of North China craton. Here, we show that from 240 to 165 Ma ago the roughly coeval continental collisions of South China to the south and Mongolia to the north ruptured the Tanlu fault within the then thick North China craton. A large ~450 km displacement mechanically induced by a ~16° intracratonic rotation along the Tanlu fault reconciles the offsets of geological piercing points and palaeomagnetic data of North China on either side of the fault. Shortly after the displacement of the only large young strike‐slip cratonic fault, the cratonic lithosphere of eastern North China collapsed.

Middle Jurassic intracontinental evolution of East Asia: Insights from the Tianshifu-Dongyingfang basin of the Liaodong Peninsula, NE China

AbstractThe Middle Jurassic intracontinental shortening event in East Asia, known as episode A of the Yanshanian Movement in the eastern North China Craton and the first phase of the Daebo Orogeny in the Korean Peninsula, respectively, has been thoroughly studied during the past two decades. However, the timing of its beginning, duration, and deformational processes are still highly controversial because few studies have probed the correlations between episode A of the Yanshanian Movement and the first phase of the Daebo Orogeny. The Tianshifu-Dongyingfang basin, located in the northern Liaodong Peninsula, is filled with complete Jurassic sequences that can be compared with those in the eastern North China Craton to the west of the Tan-Lu fault zone and the Korean Peninsula. Regional stratigraphic correlations suggest that the Tianshifu-Dongyingfang basin contains not only the syntectonic conglomerates, but also the lower and upper unconformities A1 and A2 of episode A of the Yanshanian Movement, which separated the syntectonic conglomerates from the underlying Early–Middle Jurassic coal measures and the overlying Late Jurassic red beds, respectively. Detailed field survey and structural analysis show that the development of syntectonic conglomerates and unconformities A1 and A2 were controlled by the imbricate thrust fault system in the basement, which resulted from the WNW–ESE compression inversed from the fault-slip data. The youngest detrital zircon U-Pb ages obtained near unconformities A1 and A2 show that the WNW–ESE compression of episode A of the Yanshanian Movement in the Liaodong Peninsula initiated at ca. 171 Ma and ended at least by 163 Ma. Our new structural and geochronological data, combined with data from the neighboring areas, suggest that episode A of the Yanshanian Movement and the first phase of the Daebo Orogeny belong to a single intracontinental shortening event, the compressional deformation of which was derived from the westward, lowangle subduction of the Paleo-Pacific plate and transmitted to the Korean and Liaodong Peninsulas at ca. 172–170 Ma and to the eastern North China Craton to the west of the Tan-Lu fault zone at 170–165 Ma.

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Seismic evidence for crustal modification across the Tanlu fault zone in eastern China

Deformation history of the Feidong Segment of the Tan–Lu Fault zone in the Early Cretaceous: Implications for the tectonic evolution in eastern China

The Tan–Lu Fault zone (TLFZ) is the largest fault zone in eastern China and a typical and representative structure of the Circum–Pacific tectonic domain. The Late Mesozoic tectonic evolution of the TLFZ is greatly significant, since it revealed the Jurassic–Cretaceous tectonic evolution of eastern China and the subduction history of the Palaeo–Pacific Plate. However, its tectonic evolution in the Early Cretaceous remains controversial. Based on geological mapping, microstructural analysis, and LA–ICP–MS zircon U–Pb dating, we constrained the deformation history of the Feidong Segment of the TLFZ in the Early Cretaceous. Results showed that the Feidong Segment of the TLFZ experienced a strong sinistral strike–slip movement at the beginning of the Early Cretaceous (~143 Ma); it was subsequently subjected to normal faulting during the Early Cretaceous (135–102 Ma), which controlled the strong magmatic activities within the Feidong area. At the end of the Early Cretaceous (~100 Ma), a weak sinistral strike–slip movement occurred again along the TLFZ. The deformation temperatures of the two sinistral strike–slip shearing stages were 500–550°C and 400–450°C, respectively. The regional comparison indicated that the Early Cretaceous tectonic evolution of the TLFZ was actually the epitome of the contemporaneous tectonic evolution of eastern China and was the result of strain localization in the Cretaceous tectonic framework of eastern China.

Generation of REE-rich syenite-(carbonatite) complex through lithosphere-asthenosphere interaction: An in-situ Sr–Nd–O isotopic study of the Mesozoic Weishan pluton, Northern China

Carbonatite-alkaline complexes are commonly derived from the mantle. However, whether the source is lithospheric or asthenospheric mantle remains debated. In order to better understand this issue, this paper conducts a Sr-Nd-O isotopic study on the Early Cretaceous, Weishan REE-rich syenite-(carbonatite) complex, Northern China. Two types of apatite are identified from the Weishan complex, namely magmatic and xenocrystic apatite. In-situ Sr-Nd isotopic analyses on magmatic apatite yielded (87Sr/86Sr)i from 0.70690 to 0.70719, and εNd(t) from −7.6 to −8.8. The pristine calcite from carbonatite has similar (87Sr/86Sr)i (0.70727–0.70739) with magmatic apatite. In-situ oxygen isotopic analyses on zircon yielded δ18OVSMOW(‰) from 5.9 to 6.7 ‰. Previous studies reveal that coeval, mantle lithosphere-derived rocks in the region have more enriched Sr (87Sr/86Sri greater than 0.709) and Nd [εNd(t) 〈 −1 2] isotopes than the Weishan complex; whereas the asthenosphere-derived rocks in the region are characterized by depleted Sr-Nd isotopes (87Sr/86Sri < 0.706; εNd(t) greater than 0) and low δ18OVSMOW values (mostly < 5.4 ‰). It is well known that Northern China experienced destruction in the Early Mesozoic, which was accompanied with asthenosphere upwelling along trans-lithosphere faults. Considering that the Weishan complex locates adjacent to the trans-lithosphere Tanlu fault, generation of the complex may be related to asthenosphere-lithosphere interaction. Notably, the Weishan complex differs from coeval REE-barren carbonatites in that its source involved asthenosphere-derived components; hence, involvement of asthenosphere-derived components may be important for the formation of such a REE-rich complex. In general, this study highlights the importance of lithosphere-asthenosphere interaction in supplying necessary heat and materials for the generation of the Weishan complex.

Structural Characteristics and Tectonic Evolution of the Wunansha Uplift in the South Yellow Sea Basin, China

By selecting typical seismic sections to carry out detailed structural interpretation, the structural style features of the Wunansha Uplift in the South Yellow Sea basin were systematically combined, and the compressional structures (imbricate, opposite/back thrust, and Y-shaped structures), strike-slip faults (positive flower-shaped faults), and extensional normal faults (listric-shaped normal faults) were identified. On this basis, combined with the characteristics of the regional stress field and the background of deep geodynamics, the genetic mechanism and structural evolution of the structural style in the Wunansha Uplift were defined. The stress mechanism of the compressional structures originated from the initial high-speed and low-angle NW subduction of the paleo-Pacific plate during the early Yanshanian movement in the Early Jurassic. The regional strike-slip fault was mainly a positive flower structure with compression and torsion characteristics, and its stress mechanism originated from sinistral shear caused by the Early Cretaceous low-angle NNW subduction of the paleo-Pacific plate. The Tan-Lu fault in eastern China also had sinistral shear characteristics in this period. The extensional normal fault was characterized by a listric shape, which developed along the northern boundary of the Wunansha Uplift, that is, the connection between the Wunansha Uplift and the Southern Depression of the South Yellow Sea basin. The stress mechanism was derived from the transition of the paleo-Pacific plate from low-angle to high-angle subduction during the late Yanshanian movement in the Late Cretaceous. Simultaneously, the tectonic stress system in eastern China also changed from compressional to tensional.

Structural restoration of an Eo-Mesoarchean (3.8–2.9 Ga) terrane, Eastern China, dissected by the Tanlu fault zone

Ancient gneissic terranes are critical rare materials that can reveal the Earth's early crustal evolution. This paper presents reconstruction of the oldest Eo-Mesoarchean gneissic terrane (3.8–2.9 Ga) in the eastern North China Craton that was partitioned by the ENE-WSW striking Tanghe-Hanling strike-slip fault (THF). The THF is a splay off the Tanlu fault zone and has been traced for 130 km and is 1–1.5 km wide. The THF has a 28 km sinistral offset, which has been established by detailed field observation. Restoring the 28 km offset, means that: (1) A sizeable potential area is recognized for searching for more 3.8–2.9 Ga Eo-Mesoarchean rocks; (2) A large NW-striking late Archean BIF belt is correlated with another at Anshan. Our data integrate with regional structural information of the Tanlu fault zone; we suggested that the Tanlu fault zone has an eastwards-fan splay pattern geometric feature in its northern part. Accordingly, we further restore the ancient tectonic configuration of eastern Asia before the Tanlu fault zone initiation. Eo-Mesoarchean rocks and 2.7–2.9 Ga terranes cropping out in Eastern Block of the North China Craton are arranged in line with NNW-SSE strike, which is consistent with their oriented gneissic foliations.

Crustal structures beneath the Northern Jiangsu Basin and its surrounding areas: implications for geothermal prospecting

Abstract Based on the recordings of 42 permanent seismic stations in Northern Jiangsu Basin (NJB) and its surrounding areas, we obtained both the sediment and crustal thickness in the region, using the nearest-neighbor algorithm and H–κ stacking method of receiver functions. We proposed a solution to use the sediment thickness to correct the depth of actual Moho discontinuity beneath the basin areas. Our results indicate that the sediment thickness in the northwest of the NJB is &amp;lt;1 km. We suggest that the southeastern border of the NJB should extend to the Yangzhou-Rudong area. The results of Moho variations show that the undulations of the Moho beneath the western NJB retains the traces of the sinistral shearing movement of the Tan-Lu Fault since the Miocene. Finally, we suggest the area around the Gaoyou city to be a prospective area for geothermal exploration.

Superposition of two orthogonal transpressions: An example from the oblique convergent margin adjoining the Tan–Lu Fault Zone, eastern China

Deformation in oblique convergent margins, especially non-plane deformation in décollement belts within such a margin, is not fully understood. The northern Zhangbaling tectonic belt represents an oblique convergent margin to the east of the NNE–SSW-striking Tan–Lu Fault Zone that separates the Yangtze Block to the east from the North China Craton to the west, and it provides a good opportunity to understand deformation in the margin. The tectonic belt consists of a fold-and-thrust belt in the east and a low-angle ductile décollement belt in the west. The fold-and-thrust belt in the marginal cover rocks indicates a pure shear-dominated deformation, and the fold axes rotated with the long axis of the horizontal finite strain ellipse. The underlying décollement belt was involved in a non-plane deformation owing to the superposition of wrenching along the Tan–Lu Fault Zone and horizontal décollement shearing. The horizontal décollement shearing dominated in the development of the flat-lying foliation, whereas the wrenching mostly dominated in the development of stretching lineations. Top-to-the-SSW sense of shear dominates in the central to southern parts of the décollement belt, whereas top-to-the-SSE sense of shear is widely present in the northern part of the belt and locally in other parts. Partitioning of the non-plane deformation is shown by kinematic partitioning within the originally flat-lying décollement belt, and it is different from the strain partitioning in a transpressional zone involved in plane deformation. The structural and geochronological data for the oblique convergent margin are consistent with sinistral faulting of the initial Tan–Lu Fault Zone during the Triassic.

Distribution characteristics and processes along flow paths of shallow groundwater in the Tan-Lu fault zone in Anhui province, China

Distribution characteristics and processes along flow paths of shallow groundwater in the Tan-Lu fault zone in Anhui province, China

Tectonic controls on geomorphological dynamics and sediment dispersal in source-to-sink systems in the Qingdong Sag, Bohai Bay Basin

Well-log and three-dimensional (3D) seismic data are used to investigate the tectonic controls during the depositional periods of the Kongdian and Shahejie formations from Ek–Es 4 L to Es 4 U–Es 3 L–M on strata distribution, depositional systems and sediment dispersal in the Qingdong Sag, Bohai Bay Basin, East China, from a source-to-sink perspective. This tectonic transition is characterised by the Tanlu Fault switching from sinistral to dextral strike-slip as the fault system changed from a dominant NW–WNW trend during the Ek–Es 4 L period to a dominant WNW–EW trend during the Es 4 U and Es 3 L–M periods. These changes subsequently controlled the framework and areal extent of sediment dispersal in the inner-basin source-to-sink systems and resulted in a change in trend of inner-basin secondary structural belts, from primarily being NW-trending during the Ek–Es 4 L period to E–W-trending during the Es 4 U and Es 3 L–M periods. The tectonic transition also resulted in the western and southern source-to-sink systems expanding with time and controlled the flow path and sediment redistribution within each source-to-sink system with migration of the subsidence centre of the Qingdong Sag and even the region. The significant changes in the basin structure controlled the source area, flow path, sediment transport distance and direction, and have a significant impact on the interpretation of depositional environments and reservoirs in rift basins with a multi-phase evolution history. KEY POINTS The Qingdong Sag, Bohai Bay Basin, experienced a tectonic transition during sediment deposition in the Eocene. The tectonic transition resulted in changes to the fault system and basin geomorphology. Fault movement and changes in basin geomorphology affected source-to-sink systems.

Seismic evidence for crustal modification across the Tanlu fault zone

Seismic evidence for crustal modification across the Tanlu fault zone