*3.3.1. SSDSs in the deep drilling cores in the Manjiaer depression and Tazhong uplift*

Tarim Basin is the largest, very complex, oil-bearing, superimposed marine facies and continental facies basin (560,000 km2 ), in north-western China. It is surrounded by the Tianshan-Beishan, West Kunlun and Altyn Tagh mountain belts to the north, south, and southeast, respectively (**Figure 7**). The basin has undergone a long geological evolution with multi-phase tectonic movements from the Neoproterozoic to the Quaternary. The Soft Sediment Deformation Structures Triggered by the Earthquakes: Response to the High… http://dx.doi.org/10.5772/intechopen.72941 113

shaking, and gravity differentiation took place and sands or silts (the denser material) sank into the underlying (less dense) mud beds to form load-cast structures that evolved into 'ball-

Droplets and cusp anticlines occurred in the first event layer, about 60-cm-thick sandstone layer, of the Kangsu formation. Droplets and cusp anticlines resulted from strongly liquidised sandstone grains migrated vertically up and down during earthquake [45]. Seventeen intensively-distributed droplets can be seen within a distance of 170 cm along the sandstone layer (**Figure 6C** and **D**). They are revealed as cylinders and drops, with elongated U-type synclines in vertical cross sections and wavy laminates, presenting the trace of liquefaction flowing. Directions of axial planes of syncline-shaped laminae in each droplet are out of order, upright, oblique and curve, suggesting that downward displacement of sand grains is random and without sliding of sand bodies on slope. Cusp anticlines are similar to diapirs in configuration of structures but different to diapiric structures. The diapiric structure refers to the underlying liquefied sand bed puncture into overlying soft sediments, while cusps are the result of liquefaction sands migrated upwards within liquefied sand layer with corn-shape body and without distinct xenolith in nucleus (**Figure 6C** and **D**). Droplets and cusp anticlines are formed under the duel effects by liquefaction and gravity. Groups of droplets resulting from superimposition of droplets and cusp anticlines resulting from upward movement of liquefying sandstone constitute multilayer complex deformation layers, which are generally explained to be triggered

*3.2.2. The activity of Talas-Ferghana strike-slip fault during the late early Jurassic*

6.5–7 of the paleo-earthquake magnitudes were estimated.

continental facies basin (560,000 km2

Three deformation layers of the Kangsu formation in the Lower Jurassic in Wuqia Basin had differences of deformation mechanisms (**Figure 5b**). The first deformation layer was characterised by droplet and cusp structures resulted from vertical liquefied displacement; the second was mainly homogeneous layers of liquefied sands and local unconformity and the third was mainly load casts and ball-and-pillow resulted from the effects of gravity and seismic shaking. Therefore, three seismic events suggest that the Talas-Ferghana strike-slip fault zone occurred due to at least three times large-scale active events during the late early Jurassic, with the different paleo-stresses imposed on soft sediments and made them deformed. According to the recorded data of liquefaction of sand layers by modern earthquakes and previous earthquakes [20, 30, 46], the SSDS were 45 to 50 km away from the Talas-Ferghana fault, and Ms

**3.3. Triggered by the early Palaeozoic activities of interior faults of the Tarim Basin**

Tarim Basin is the largest, very complex, oil-bearing, superimposed marine facies and

the Tianshan-Beishan, West Kunlun and Altyn Tagh mountain belts to the north, south, and southeast, respectively (**Figure 7**). The basin has undergone a long geological evolution with multi-phase tectonic movements from the Neoproterozoic to the Quaternary. The

), in north-western China. It is surrounded by

*3.3.1. SSDSs in the deep drilling cores in the Manjiaer depression and Tazhong uplift*

and-pillow structures' or pseudonodules [28, 32, 35].

112 Tectonics - Problems of Regional Settings

by earthquakes.

**Figure 7.** Schematic map of the structural units of the Tarim Basin, showing the location of deep drilling wells in Tazhong uplift and Manjiaer depression, in which various SSDSs of the Ordovician and Silurian are observed.

early Palaeozoic is the main period of development, especially in the central parts of the basin. During the first tectonic cycle, which is from the latest Neoproterozoic to the Middle Devonian, two unconformities that are Silurian/Upper Ordovician and Upper Devonian-Carboniferous/pre-Upper Devonian unconformity were formed during the middle and late Caledonian tectonic movements [49–53]. The properties of main faults changed from the normal faulting to reverse faulting during the middle Caledonian movement. The paleo-tectonic activities of this area are key issues and remain enigmatic for understanding the basin reconstructions and hydrocarbon explorations.

From the Ordovician to Silurian, the sedimentation (**Figure 8**) took place in a marine basin facies, shelf-and-platform (**Figure 8b**) and tidal-flat facies (**Figure 8a**) depositional environment in the Tazhong Uplift and the Manjiaer Depression. Various millimetre-, centimetre- and metre-scale soft-sediment deformation structures (SSDSs) have been identified in the Upper Ordovician and Lower-Middle Silurian from deep drilling cores in the Tazhong Uplift and the Manjiaer Depression (**Figure 7**). They include liquefied sand veins, liquefaction-induced breccia, boudinage-like structures, load and diapir- or flame-like structures, dish and mixed-layer structures, hydroplastic convolutions and seismic unconformities (**Figure 8**). They were commonly mistaken for worm traces, mud cracks or storm deposits since they have abrupt contacts with the surrounding sedimentary rock (according to the geological well reports).

*3.3.1.1. Liquefied sand veins and liquefaction-induced breccias*

*3.3.1.2. Boudinage-like SSDS and boudinage-like breccias*

Liquefied sand veins are common in the studied cores and have been identified in many wells (**Figure 8**). These liquefied sand veins are a vein-type structure that is formed by injection of liquefied sand flow. Unconsolidated near-surface sands that are water-saturated may liquefy when are abruptly loaded or shaken. This results in overpressure of the pore water, which may then escape to adjoining lower pressure intervals by forming injection features in otherwise undisturbed deposition. Liquefied sand veins in the MD1, TZ29, SH2 and Z12 wells range in width from 2 mm to ~ 3 cm and their length ranges from 1 cm to over 10 cm. They consist of laminated thick horizontal mud layers interbedded with thin silty or fine sand layers, the grey silty sand liquefied and emplaced grey black mud beds. Liquefied sand flows have two occurrences: vertically liquefied (**Figure 8B**) and lateral liquefied (**Figure 9A**). The veins are irregularly curved, with bifurcation in cross section, and without a uniform planar direction as plate in 3D morphology. The textures and components of the sand veins are similar and differ obviously from the surrounding mudstones. Liquefied sand veins cut through mud beds and trigger arching or concave bending (**Figure 9A**, **D** and **E**) of the surrounding laminated mud beds. Thin interbedded sand and mud can form multilayered, interpenetrated and complex vein, like the liquefied sand veins of SH2 well on Silurian composed of ochre sands (fine sands or silty sands) liquefied and invaded in the over- and underlying brown muds. Some of the liquefied sand veins are associated with liquefaction-induced breccias.

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Liquefaction-induced breccias are produced by liquefaction of sands that are both overlain and underlain by mud layers. Liquefaction of the sand causes disruption of the surrounding mud beds into gravel-sized, clayey breccia fragments. Liquefaction-induced breccias occur together with liquefied sand veins (**Figures 9A** and **10A**). Grey silty gravels were confined by black grey mudstones; breccias are components of grey green silty mudstones and siltstone fragments with angular and assorted sizes of gravel particles ranging from 0.3 to 1 cm. Such breccias have been interpreted as genetic of storm flow (taken from the final well report) by the mixed and disorderly sedimentary breccias intercalated into the undeformed stable layers. However, the breccias were formed in the mud layers by invasion, ripping up and truncating by liquefied sand veins. The breccias are in-situ and non-transportation. **Figure 10D** shows a liquefied gravel-bearing sand veins and a micro-thrust fault coexisted deformation structure.

Boudinage-like soft-sediment deformation structures (BSSDS) are for the first time identified in the Upper Ordovician in Manjiaer depression and the metre-scale deformation structures in vertical stratigraphic sequences. They consist of thin, light grey calcareous siltstones interbedded with dark grey calcareous mudstones deposited in mixing siliciclastic and carbonate shelf environment. The unconsolidated sediments under horizontal shear stress form boudinage-like structures, rapid depositing sediments with large thicknesses and undeform layers with similar properties on lithology and sedimentary intervals. Multiple cycles of BSSDS are identified in the TZ32 and TZ33 wells (**Figures 8B** and **9B**). The calcareous sand beds with

**Figure 8.** Correlation of strata and paleo-seismic records in the Silurian (a) and Upper Ordovician (b) in the central part of the Tarim Basin (modified from [54]), showing the types and layers of observed SSDS.

#### *3.3.1.1. Liquefied sand veins and liquefaction-induced breccias*

Liquefied sand veins are common in the studied cores and have been identified in many wells (**Figure 8**). These liquefied sand veins are a vein-type structure that is formed by injection of liquefied sand flow. Unconsolidated near-surface sands that are water-saturated may liquefy when are abruptly loaded or shaken. This results in overpressure of the pore water, which may then escape to adjoining lower pressure intervals by forming injection features in otherwise undisturbed deposition. Liquefied sand veins in the MD1, TZ29, SH2 and Z12 wells range in width from 2 mm to ~ 3 cm and their length ranges from 1 cm to over 10 cm. They consist of laminated thick horizontal mud layers interbedded with thin silty or fine sand layers, the grey silty sand liquefied and emplaced grey black mud beds. Liquefied sand flows have two occurrences: vertically liquefied (**Figure 8B**) and lateral liquefied (**Figure 9A**). The veins are irregularly curved, with bifurcation in cross section, and without a uniform planar direction as plate in 3D morphology. The textures and components of the sand veins are similar and differ obviously from the surrounding mudstones. Liquefied sand veins cut through mud beds and trigger arching or concave bending (**Figure 9A**, **D** and **E**) of the surrounding laminated mud beds. Thin interbedded sand and mud can form multilayered, interpenetrated and complex vein, like the liquefied sand veins of SH2 well on Silurian composed of ochre sands (fine sands or silty sands) liquefied and invaded in the over- and underlying brown muds. Some of the liquefied sand veins are associated with liquefaction-induced breccias.

Liquefaction-induced breccias are produced by liquefaction of sands that are both overlain and underlain by mud layers. Liquefaction of the sand causes disruption of the surrounding mud beds into gravel-sized, clayey breccia fragments. Liquefaction-induced breccias occur together with liquefied sand veins (**Figures 9A** and **10A**). Grey silty gravels were confined by black grey mudstones; breccias are components of grey green silty mudstones and siltstone fragments with angular and assorted sizes of gravel particles ranging from 0.3 to 1 cm. Such breccias have been interpreted as genetic of storm flow (taken from the final well report) by the mixed and disorderly sedimentary breccias intercalated into the undeformed stable layers. However, the breccias were formed in the mud layers by invasion, ripping up and truncating by liquefied sand veins. The breccias are in-situ and non-transportation. **Figure 10D** shows a liquefied gravel-bearing sand veins and a micro-thrust fault coexisted deformation structure.

#### *3.3.1.2. Boudinage-like SSDS and boudinage-like breccias*

**Figure 8.** Correlation of strata and paleo-seismic records in the Silurian (a) and Upper Ordovician (b) in the central part

of the Tarim Basin (modified from [54]), showing the types and layers of observed SSDS.

114 Tectonics - Problems of Regional Settings

Boudinage-like soft-sediment deformation structures (BSSDS) are for the first time identified in the Upper Ordovician in Manjiaer depression and the metre-scale deformation structures in vertical stratigraphic sequences. They consist of thin, light grey calcareous siltstones interbedded with dark grey calcareous mudstones deposited in mixing siliciclastic and carbonate shelf environment. The unconsolidated sediments under horizontal shear stress form boudinage-like structures, rapid depositing sediments with large thicknesses and undeform layers with similar properties on lithology and sedimentary intervals. Multiple cycles of BSSDS are identified in the TZ32 and TZ33 wells (**Figures 8B** and **9B**). The calcareous sand beds with

little difference of the upper and lower sediments. The discontinuous undulate surfaces are easily produced at the boundary, and the sediments of the upper unit form ground fissure, load cast, ball-and-pillow at the top of the lower unit. Spherical, mushroom-shaped and ellipsoidal bodies (**Figure 10B**) of the lower unit also invaded the upper unit by liquefaction and diapirism.

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**Figure 10.** Typical SSDSs in the deep drilling cores (2) of Kepingtage Formation of the Lower Silurian, in well SH9, central part of the Tarim basin. (A) Liquefied breccia and liquefied sand veins, dark grey muds were brecciaed vertically or horizontally by light grey silts emplaced, depth 5590.15 m. (B) Complex plunged sediment mixtures, the wavy interface and load cast were formed, with some light sand layers and light celadon liquefied sand veins, depth at 5342 m. (C) Thixotropic diapir, showing that the dark grey muds experienced thixotropy upward movement to the upper light grey silt sands and formed diapir structures, which were intercalated by the overlying and underlying non-deformation flatting dark grey mud layers and light grey silt layers, showing a complete non-seismic, in-seismic, and non-seismic sequence vertically; well SH9, depth 5606 m. (D) Liquefied gravel-bearing sand veins and a micro-thrust fault, liquefied light grey sand with brown fine gravels and cut the laminated grey mud layer, and superimposed by mini-type thrust

fault, depth 5339.69 m. Red arrows indicate the orientation of rheology of particulate matter.

**Figure 9.** Typical SSDSs in the deep drilling cores (1), in the central part of the Tarim basin. (A) Concentration of sand veins, well SH2, depth 5567.3 m; Yimugantawu Formation of the Middle Silurian (S2*y*). (B) Boudinage-like soft-sediment deformation structures (B-SSDS) and small liquefied sand veins, well TZ32, depth 4507.5 m, Upper Ordovician. (C) Mixed-layer structures, well Z12, depth 4713.8 m; Yimugantawu Fm. Of the middle Silurian. (D and E) Sand veins in cross section and plane, well SH2, depth 5573.1 m; stratigraphical unit S2*y*.

comparatively higher cohesive muds were sheared and cut off, to form lenticular sand bodies under tensional shear stresses.

#### *3.3.1.3. Plunged sediment mixtures*

Plunged sediment mixtures refer to the deformation that occurs near or on the boundary between two different unconsolidated stratigraphic units [54]. These two units usually have little difference of the upper and lower sediments. The discontinuous undulate surfaces are easily produced at the boundary, and the sediments of the upper unit form ground fissure, load cast, ball-and-pillow at the top of the lower unit. Spherical, mushroom-shaped and ellipsoidal bodies (**Figure 10B**) of the lower unit also invaded the upper unit by liquefaction and diapirism.

**Figure 10.** Typical SSDSs in the deep drilling cores (2) of Kepingtage Formation of the Lower Silurian, in well SH9, central part of the Tarim basin. (A) Liquefied breccia and liquefied sand veins, dark grey muds were brecciaed vertically or horizontally by light grey silts emplaced, depth 5590.15 m. (B) Complex plunged sediment mixtures, the wavy interface and load cast were formed, with some light sand layers and light celadon liquefied sand veins, depth at 5342 m. (C) Thixotropic diapir, showing that the dark grey muds experienced thixotropy upward movement to the upper light grey silt sands and formed diapir structures, which were intercalated by the overlying and underlying non-deformation flatting dark grey mud layers and light grey silt layers, showing a complete non-seismic, in-seismic, and non-seismic sequence vertically; well SH9, depth 5606 m. (D) Liquefied gravel-bearing sand veins and a micro-thrust fault, liquefied light grey sand with brown fine gravels and cut the laminated grey mud layer, and superimposed by mini-type thrust fault, depth 5339.69 m. Red arrows indicate the orientation of rheology of particulate matter.

comparatively higher cohesive muds were sheared and cut off, to form lenticular sand bodies

**Figure 9.** Typical SSDSs in the deep drilling cores (1), in the central part of the Tarim basin. (A) Concentration of sand veins, well SH2, depth 5567.3 m; Yimugantawu Formation of the Middle Silurian (S2*y*). (B) Boudinage-like soft-sediment deformation structures (B-SSDS) and small liquefied sand veins, well TZ32, depth 4507.5 m, Upper Ordovician. (C) Mixed-layer structures, well Z12, depth 4713.8 m; Yimugantawu Fm. Of the middle Silurian. (D and E) Sand veins in

Plunged sediment mixtures refer to the deformation that occurs near or on the boundary between two different unconsolidated stratigraphic units [54]. These two units usually have

under tensional shear stresses.

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cross section and plane, well SH2, depth 5573.1 m; stratigraphical unit S2*y*.

*3.3.1.3. Plunged sediment mixtures*

#### *3.3.1.4. Thixotropy wedge and diapir*

Thixotropic wedges usually develop in fine-grain sediments, which are thixotropic flow deformation triggered by an earthquake activity [14, 20]. While the soft sediments (mud, soft siliceous sediment and carbonate ooze) with the grain size are less than 0.005 mm, the strength of finegrain sediments and clays decrease owing to seismic shear stress effect, resulting in the complex rheological phenomenon that occurs (**Figure 10C**). Three axis vibration test of saturated soft soil presents when the seismic intensity is 7 or greater (amount to the earthquake magnitude is 5.6), and muds usually do not be liquefied but it happens with thixotropic flow, which is triggered by shocking [55, 56]. The earthquake magnitude for thixotropic deformation is higher than liquefied deformation [57]. Many deformation structures in argillaceous rocks, silica rocks and micritic of carbonate rocks can be interpreted by the thixotropic mechanism (**Figure 10C**).

The wedges may be very narrow and are recurrent. Thixotropic wedges are obviously different with the ground fissure in hard rock layers. Thixotropic diapir indicates that mud layers flow upwards with thixotropy owing to shock and intrude or emplace in the fine sand or silt layers (**Figure 10C**).

#### *3.3.2. SSDSs triggered by the paleo-activities of the Tazhong 1 and secondary faults*

During the late Ordovician to early Silurian, the Tarim Basin underwent conversion from a tensional to a compressive flexural tectonic environment. Accompanied by the Proto-Tethys Ocean subducted in a northward direction since early Ordovician [58], the middle Kunlun terrain collided with the Tarim plate and the South Altun Ocean closured during the late Ordovician [59, 60]. The southern parts of the Tarim Basin was the strong deformation area, especially the southeast area [52, 53], and the main faults in the Tazhong uplift and Tangguzibas depression were activated strongly (**Figure 11**) and responded to the orogenic activities. The NW-trending Tazhong 1 fault (TZ1F) was the boundary fault between the Tazhong Uplift and the Manjiaer Depression during the late Ordovician to Middle Devonian and the paleo-active strength of fault movement was strongest during the Ordovician, with a vertical fault displacement in excess of 2 km (**Figure 11a** and **c**). The property of the TZ1F changed from the normal fault to the reverse fault at the end of the late Ordovician. The west segment of TZ1F ceased activity before or in early Silurian depositing, and the middle and south segments remained active to the early Carboniferous. The activities of the secondary reverse faults of the TZ1F were dominated during the Silurian. At the same time, a series of NE-trending small faults were active but the displacements were little (**Figure 11b**). The normal and strike-slip property of these small faults had been recognised in the 3D seismic data.

Based on their characteristics, the inferred formation mechanism and the spatial association with faults, the SSDSs were triggered by the paleo-active NW-trending TZ1F and a series of NE-trending small faults. The TZ1F was a seismogenic fault during the late Ordovician, whereas the reversed-direction secondary faults and multiple small NE-trending faults were the seismogenic faults in the Early-Middle Silurian. The SSDSs triggered by the paleo-active faults may be represented as records of the high-frequency tectonic events with the pulsation

**Figure 11.** 2D seismic interpretation profiles of the Tazhong uplift and its adjacent area (A-A′, B-B′), (c) the fault systems of the Silurian in the Tazhong uplift and its adjacent areas (modified after Northwest Oilfield Company of SINOPEC,

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**3.4. Triggered by the Mesoproterozoic earthquake activities in the northern margin** 

The SSDSs of the Mesoproterozoic in the Yan-Liao Aulacogen, which is located in the northern margin of the North China Craton, were recognised first by Song [62], and the oldest SSDSs have been observed in China [61–63]. In the Chuanlinggou and Gaoyuzhuang Formation of the Changcheng System (1800–1400) and Wumishan Formation of the Jixian

and circularity during the main tectonic movement phases.

2015), showing the identified seismic event layers in the deep drilling cores.

*3.4.1. SSDSs of the Mesoproterozoic in the Yan-Liao Aulacogen*

**of the North China Craton**

These SSDSs, which are intercalated by undeformed layers with similar lithology and sedimentary facies, are observed with wide distribution near the faults (**Figures 7, 8** and **11**). So the SSDSs resulted from the bursting events after they were deposited but incompletely consolidated. Most of them (Well SH2, TZ33, TZ29 and TZ32) in the Upper Ordovician are in the drilling cores nearby the TZ1F and a little in the farther wells (MD1 and TD1). About 51 layers of SSDSs have been observed in the 1500 m sedimentary layers of the Upper Ordovician (deposited during 447–444 Ma) and 26 layers of SSDSs have been observed in about 800 m sedimentary layers of the Lower Silurian (deposited during 436–421 Ma) (**Figure 11c**). Soft Sediment Deformation Structures Triggered by the Earthquakes: Response to the High… http://dx.doi.org/10.5772/intechopen.72941 119

*3.3.1.4. Thixotropy wedge and diapir*

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layers (**Figure 10C**).

Thixotropic wedges usually develop in fine-grain sediments, which are thixotropic flow deformation triggered by an earthquake activity [14, 20]. While the soft sediments (mud, soft siliceous sediment and carbonate ooze) with the grain size are less than 0.005 mm, the strength of finegrain sediments and clays decrease owing to seismic shear stress effect, resulting in the complex rheological phenomenon that occurs (**Figure 10C**). Three axis vibration test of saturated soft soil presents when the seismic intensity is 7 or greater (amount to the earthquake magnitude is 5.6), and muds usually do not be liquefied but it happens with thixotropic flow, which is triggered by shocking [55, 56]. The earthquake magnitude for thixotropic deformation is higher than liquefied deformation [57]. Many deformation structures in argillaceous rocks, silica rocks and micritic of carbonate rocks can be interpreted by the thixotropic mechanism (**Figure 10C**). The wedges may be very narrow and are recurrent. Thixotropic wedges are obviously different with the ground fissure in hard rock layers. Thixotropic diapir indicates that mud layers flow upwards with thixotropy owing to shock and intrude or emplace in the fine sand or silt

*3.3.2. SSDSs triggered by the paleo-activities of the Tazhong 1 and secondary faults*

During the late Ordovician to early Silurian, the Tarim Basin underwent conversion from a tensional to a compressive flexural tectonic environment. Accompanied by the Proto-Tethys Ocean subducted in a northward direction since early Ordovician [58], the middle Kunlun terrain collided with the Tarim plate and the South Altun Ocean closured during the late Ordovician [59, 60]. The southern parts of the Tarim Basin was the strong deformation area, especially the southeast area [52, 53], and the main faults in the Tazhong uplift and Tangguzibas depression were activated strongly (**Figure 11**) and responded to the orogenic activities. The NW-trending Tazhong 1 fault (TZ1F) was the boundary fault between the Tazhong Uplift and the Manjiaer Depression during the late Ordovician to Middle Devonian and the paleo-active strength of fault movement was strongest during the Ordovician, with a vertical fault displacement in excess of 2 km (**Figure 11a** and **c**). The property of the TZ1F changed from the normal fault to the reverse fault at the end of the late Ordovician. The west segment of TZ1F ceased activity before or in early Silurian depositing, and the middle and south segments remained active to the early Carboniferous. The activities of the secondary reverse faults of the TZ1F were dominated during the Silurian. At the same time, a series of NE-trending small faults were active but the displacements were little (**Figure 11b**). The normal and strike-slip property of these small faults had been recognised in the 3D seismic data. These SSDSs, which are intercalated by undeformed layers with similar lithology and sedimentary facies, are observed with wide distribution near the faults (**Figures 7, 8** and **11**). So the SSDSs resulted from the bursting events after they were deposited but incompletely consolidated. Most of them (Well SH2, TZ33, TZ29 and TZ32) in the Upper Ordovician are in the drilling cores nearby the TZ1F and a little in the farther wells (MD1 and TD1). About 51 layers of SSDSs have been observed in the 1500 m sedimentary layers of the Upper Ordovician (deposited during 447–444 Ma) and 26 layers of SSDSs have been observed in about 800 m sedimentary layers of the Lower Silurian (deposited during 436–421 Ma) (**Figure 11c**).

**Figure 11.** 2D seismic interpretation profiles of the Tazhong uplift and its adjacent area (A-A′, B-B′), (c) the fault systems of the Silurian in the Tazhong uplift and its adjacent areas (modified after Northwest Oilfield Company of SINOPEC, 2015), showing the identified seismic event layers in the deep drilling cores.

Based on their characteristics, the inferred formation mechanism and the spatial association with faults, the SSDSs were triggered by the paleo-active NW-trending TZ1F and a series of NE-trending small faults. The TZ1F was a seismogenic fault during the late Ordovician, whereas the reversed-direction secondary faults and multiple small NE-trending faults were the seismogenic faults in the Early-Middle Silurian. The SSDSs triggered by the paleo-active faults may be represented as records of the high-frequency tectonic events with the pulsation and circularity during the main tectonic movement phases.

## **3.4. Triggered by the Mesoproterozoic earthquake activities in the northern margin of the North China Craton**

#### *3.4.1. SSDSs of the Mesoproterozoic in the Yan-Liao Aulacogen*

The SSDSs of the Mesoproterozoic in the Yan-Liao Aulacogen, which is located in the northern margin of the North China Craton, were recognised first by Song [62], and the oldest SSDSs have been observed in China [61–63]. In the Chuanlinggou and Gaoyuzhuang Formation of the Changcheng System (1800–1400) and Wumishan Formation of the Jixian

**Figure 12.** (A) Paleo-plate sketch map of China, showing the distribution of the major paleo-plates of different ages (after [62]). (B) Paleo-geographical map of the Yan-Liao Aulacogen from the Proterozoic Gaoyuzhuang Stage to the Wumishan Stage showing an epicontinental sea opened to the north, and the approximate positions of the discovered seismites (after [63–66]). The identified outcrops of earthquake-triggered SSDSs are marked by stars, 1—[60]; 2—[67]; 3—[68]; 4 and 5—[64]; 6—[32, 69]; 7—[66]. The red stars show the position of the seismites in this paper. (C) Lithostratigraphy of the Mesoproterozoic of the Yan-Liao Aulacogen (modified from [66–74, 77–79]), the records of multiple paleo-earthquake events in green words and volcanic events in black words are shown.

System, various SSDSs have been observed, which mainly developed in the epicontinental sea (**Figure 12**). They are liquefied sand veins, liquefied carbonate mounds, liquefied breccia, hydroplastic deformation, various curly deformation, looping bedding and graded faults. Deformed layers are separated by the undeform layers. The SSDSs in the Chuanlinggou Formation are composed of clastic rocks in the intertidal and subtidal environments, and the others are composed of carbonate rocks deposited in carbonate platform (**Figure 12C**).

#### *3.4.1.1. Liquefaction mound and carbonate sand volcano*

They are typical SSDSs in the Wumishan Formation (1550–1400 Ma) of the Mesoproterozoic, with the mound and crater in shape (**Figure 13a**–**c**), linear arrangement along a roadcut near Zhuanghuwa Village, ca. 70 km west of Beijing. Liquefaction mounds have generally rounded shapes, with some concentric and radial fissures. They are composed of grey dolostone with minor amount of black siliceous (chert) rock, especially on the top of the mounds. The diameter of the mounds varies between 1.5 m and 4 m and their height from 10 cm to 30 cm. **Figure 13b** shows the best-exposed mound has an almost perfectly circular shape, with a diameter of 2.8 m, 6 concentric circular fissures and 13 radial direction

in Yongding River Valley, Beijing.

**Figure 13.** Typical seismites triggered by the Mesoproterozoic earthquakes in the Yanliao Aulacogen, the northern margin of North China Craton. (a) Linear distribution of liquefied carbonate mounds of the Wumishan Formation, the orientation of mounds paralleled to the trending of the Shijiazhuang-Lingyuan Fault of the Yanliao Aulacogen, spot 7 illustrated in **Figure 12**. (b) Close-up views of mound 1 at the Zhuanghuwa sections, note the concentric circular rings and the radial fissures (arrowed). (c) The fine-grained carbonate-sand volcano of the Wumishan Formation, Zhuanghuwa section, spot 7 illustrated in **Figure 12**. (d) Loop bedding of the Wumishan Formation in Yongding River Valley, Beijing. (e) Netlike liquefied dolomite veins and argillaceous dolomite breccia, Tuanshanzi Formation, spot 4, Tuanshanzi village, Jixian, Tianjing. (f) Plate-spine breccias and intense folds, algal dolostones, Wumishan Formation,

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**Figure 13.** Typical seismites triggered by the Mesoproterozoic earthquakes in the Yanliao Aulacogen, the northern margin of North China Craton. (a) Linear distribution of liquefied carbonate mounds of the Wumishan Formation, the orientation of mounds paralleled to the trending of the Shijiazhuang-Lingyuan Fault of the Yanliao Aulacogen, spot 7 illustrated in **Figure 12**. (b) Close-up views of mound 1 at the Zhuanghuwa sections, note the concentric circular rings and the radial fissures (arrowed). (c) The fine-grained carbonate-sand volcano of the Wumishan Formation, Zhuanghuwa section, spot 7 illustrated in **Figure 12**. (d) Loop bedding of the Wumishan Formation in Yongding River Valley, Beijing. (e) Netlike liquefied dolomite veins and argillaceous dolomite breccia, Tuanshanzi Formation, spot 4, Tuanshanzi village, Jixian, Tianjing. (f) Plate-spine breccias and intense folds, algal dolostones, Wumishan Formation, in Yongding River Valley, Beijing.

System, various SSDSs have been observed, which mainly developed in the epicontinental sea (**Figure 12**). They are liquefied sand veins, liquefied carbonate mounds, liquefied breccia, hydroplastic deformation, various curly deformation, looping bedding and graded faults. Deformed layers are separated by the undeform layers. The SSDSs in the Chuanlinggou Formation are composed of clastic rocks in the intertidal and subtidal environments, and the others are composed of carbonate rocks deposited in carbonate platform (**Figure 12C**).

**Figure 12.** (A) Paleo-plate sketch map of China, showing the distribution of the major paleo-plates of different ages (after [62]). (B) Paleo-geographical map of the Yan-Liao Aulacogen from the Proterozoic Gaoyuzhuang Stage to the Wumishan Stage showing an epicontinental sea opened to the north, and the approximate positions of the discovered seismites (after [63–66]). The identified outcrops of earthquake-triggered SSDSs are marked by stars, 1—[60]; 2—[67]; 3—[68]; 4 and 5—[64]; 6—[32, 69]; 7—[66]. The red stars show the position of the seismites in this paper. (C) Lithostratigraphy of the Mesoproterozoic of the Yan-Liao Aulacogen (modified from [66–74, 77–79]), the records of multiple paleo-earthquake

They are typical SSDSs in the Wumishan Formation (1550–1400 Ma) of the Mesoproterozoic, with the mound and crater in shape (**Figure 13a**–**c**), linear arrangement along a roadcut near Zhuanghuwa Village, ca. 70 km west of Beijing. Liquefaction mounds have generally

*3.4.1.1. Liquefaction mound and carbonate sand volcano*

events in green words and volcanic events in black words are shown.

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rounded shapes, with some concentric and radial fissures. They are composed of grey dolostone with minor amount of black siliceous (chert) rock, especially on the top of the mounds. The diameter of the mounds varies between 1.5 m and 4 m and their height from 10 cm to 30 cm. **Figure 13b** shows the best-exposed mound has an almost perfectly circular shape, with a diameter of 2.8 m, 6 concentric circular fissures and 13 radial direction fissures. The fissures are filled with dark siliceous chert rock. A carbonate sand volcano also remains, which is shaped just like a small volcano with a crater (**Figure 13c**). It has a diameter of 110 cm and a thickness of about 30 cm. And a thin layer of black siliceous rock is built up in the centre of the depression. There are also at least three (possibly five) radial fissures exposed, which are filled with dark siliceous material.

(Ms 8.0) in Sichuan Province, SW China in 2008. According to the mechanism of SSDSs and the relationship of the activity of SSDSs and faults, they may be triggered by paleo-seismic events of the Shijiazhuang-Lingyuan Fault Belts. There are about 29 times deformation layers or seismic event layers have been observed in the Zhuanghuwa section, and the occurrence frequency of the strong paleo-earthquakes is about 20 thousand years to 32 thousand years [78, 79]. Multiple seismic events and activities of the Shijiazhuang-Lingyuan Fault Belt are

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**4. Implication and prospects of the high-frequency tectonic events** 

The typical cases of seismites at different times in China reveal the sequence of paleo-earthquake events, and the activities of seismogenic faults can help us understand the dynamics of

Seismites research may provide geo-history evidences for active seismic fault belts. The vertical sequences of paleo-earthquakes (seismites) are separated by undeformed sedimentary layers. They will provide a history of gradual and abrupt changes of the tectonic development and evolution in a particular region and regular patterns of seismicity of this region. Correlation of the paleo-earthquake activity sequences will help us to know spatial and temporal characteristics of paleo-seismic events in the main tectonic movement. This will provide important supplementary evidences of the impulsive and cyclicity of tectonism of the main tectonic movement. And they can also provide evidences for the tectonic records during a period from

 to 106 yr (The white paper resulting from a workshop held at Denver Colorado, 2002), which is a difficult issue in the frontier research of structural geology and tectonic science. Paleo-earthquake events will build a link between orogenesis, high-frequency tectonism (in

Since seismites formed before sediments are completely consolidated, the age of depositing sediments in seismites could indicate the approximate time of a paleo-seismic event, and the ages of syn-depositional volcanism and organic debris in relative layers of seismites can provide evidence for the absolute age of seismicity and the tectonic events. The 14C dating (radiocarbon dating), the U-Th disequilibrium technique (speleothem calcite), the electronic spin (ESR) (fossil dating), the K-Ar and 40Ar-39Ar dating (syntectonic illite) and the detrital zircon

Paleo-seismic research may help us understand more the changes of sedimentary paleogeographic and ecological on different scales. It is a new research direction to combine paleo-earthquake, which is an unexpected and catastrophic event, with life and environmental change.

U/Pb dating (LA-MC-ICP-MS) can provide the different time-scale dating.

**4.3. Effects on paleo-ecological environments and energy resources**

responded on the break-up of the Columbian supercontinent.

**4.1. Understanding the history of fault activities**

tectonic developments in different regions.

basin-mountain system) and a seismic activity.

**4.2. Dating precisely of the tectonic events**

**studied**

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