Late Quaternary activity of Wulashan Northern fault, North China

Abstract

The Late Quaternary activity characteristics of secondary faults located between the main active faults at the boundaries of large basins are of great significance to the overall understanding of regional seismic hazards. The Wulashan Northern Fault (WNF) is located on the northern side of the Ordos Block, within the Northern Margin Fault Basin in North China, between the Sertengshan Piedmont Fault and Daqingshan Piedmont Fault. Current research on the geometry and kinematics of the WNF needs to be improved. In this study, we aimed to determine the shallow structural characteristics and Late Quaternary activity of the WNF using shallow seismic exploration and composite drilling geological cross-sectional analysis. The results indicate that the WNF is not a single surface fault but multiple branches with a northward-dipping stepped surface distribution. The latest activity of the F1 branch with a maximum coseismic vertical dislocation of 0.9 m occurred before 47.08 ± 3.7 ka B.P. The latest and older activities of the branch of F2 with a maximum coseismic vertical dislocation of 0.96 m and 1.15 m occurred before 73.8 ± 2.8 ka B.P. and 91.2 ± 4.4 ka B.P., respectively. According to a series of empirical relationships between length of surface rupture and magnitude, the maximum potential magnitude of the earthquake was determined to be M = 6.5–7.0. We argue that even though the Late Quaternary activity of the WNF was weaker than that of the other boundary faults of the Hetao Basin, the local urban and rural planning and land and resources construction in the Hetao Basin region should pay attention to the seismic risk of the WNF as an independent section in the future for the effect of secular tectonic loading.

Full text

TYPE Original Research
PUBLISHED 16 August 2024
DOI 10.3389/feart.2024.1437012
OPEN ACCESS
EDITED BY
Gang Rao,
Southwest Petroleum University, China
REVIEWED BY
Yiduo Liu,
Chinese Academy of Sciences (CAS), China
Hu Wang,
Southwest Jiaotong University, China
*CORRESPONDENCE
Weimin He,
wmhe65@163.com
RECEIVED 23 May 2024
ACCEPTED 02 August 2024
PUBLISHED 16 August 2024
CITATION
Wei L, He W, Xu Y, Du Y, Dai A, Song X, Xu S
and Qin J (2024) Late Quaternary activity of
Wulashan Northern fault, North China.
Front. Earth Sci. 12:1437012.
doi: 10.3389/feart.2024.1437012
COPYRIGHT
© 2024 Wei, He, Xu, Du, Dai, Song, Xu and
Qin. This is an open-access article distributed
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Attribution License (CC BY). The use,
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is permitted which does not comply with
these terms.
Late Quaternary activity of
Wulashan Northern fault, North
China
Leihua Wei1, Weimin He1*, Yueren Xu2, Yanlin Du1, Aopeng Dai1,
Xiaopeng Song1, Shuya Xu 1and Jingjing Qin1
1Geophysical Exploration Center, China Earthquake Administration, Zhengzhou, China, 2Institute of
Earthquake Forecasting, China Earthquake Administration, Beijing, China
The Late Quaternary activity characteristics of secondary faults located between
the main active faults at the boundaries of large basins are of great signicance to
the overall understanding of regional seismic hazards. The Wulashan Northern
Fault (WNF) is located on the northern side of the Ordos Block, within
the Northern Margin Fault Basin in North China, between the Sertengshan
Piedmont Fault and Daqingshan Piedmont Fault. Current research on the
geometry and kinematics of the WNF needs to be improved. In this study, we
aimed to determine the shallow structural characteristics and Late Quaternary
activity of the WNF using shallow seismic exploration and composite drilling
geological cross-sectional analysis. The results indicate that the WNF is
not a single surface fault but multiple branches with a northward-dipping
stepped surface distribution. The latest activity of the F1 branch with a
maximum coseismic vertical dislocation of 0.9m occurred before 47.08 ±
3.7ka B.P. The latest and older activities of the branch of F2 with a maximum
coseismic vertical dislocation of 0.96m and 1.15m occurred before 73.8 ±
2.8 ka B.P. and 91.2 ± 4.4 ka B.P., respectively. According to a series of
empirical relationships between length of surface rupture and magnitude,
the maximum potential magnitude of the earthquake was determined to be
M= 6.5–7.0. We argue that even though the Late Quaternary activity of
the WNF was weaker than that of the other boundary faults of the Hetao
Basin, the local urban and rural planning and land and resources construction
in the Hetao Basin region should pay attention to the seismic risk of the
WNF as an independent section in the future for the eect of secular
tectonic loading.
KEYWORDS
Ordos block, Wulashan northern fault, shallow seismic exploration, composite drilling
geological section, late Pleistocene activity
1 Introduction
e Ordos Block was essential for the Cenozoic and modern tectonic movements
in North China. It was an important transitional area adjacent to the northeastern
edge of the Tibetan Plateau (Zhangetal., 2003). e internal structural deformation
and seismic activity of the block were weak. Owing to the expansion and compression
of the Tibetan Plateau in the northeastern direction, and the sinking and stretching
of the North China Block, the periphery of the Ordos Block is surrounded by
a series of faults and fault basins, that is, the Hetao Basin, Shanxi Ri System
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Wei etal. 10.3389/feart.2024.1437012
FIGURE 1
Structures of the rift basins around the Ordos Block (modied after Suetal., 2023).
(SRS), Weihe Basin (WB), and Yinchuan Basin, from the northern
edge in a clockwise direction (eResearchGrouponActiveFault
SystemaroundOrdosMassif, 1988;Dengetal., 1999;Wang
etal., 2001). Except for the Hetao Basin, e four fault basins
experienced many disastrous earthquakes with M≥ 7, ve of
which had M= 8.0 or even more signicant in history (Figure1).
e strong earthquakes have caused devastating disasters to
people and the economy around each epicenter, such as the
1739A.D. M= 8.0 Pingluo earthquake in the Yinchuan Basin
(eResearchGrouponActiveFaultSystemaroundOrdosMassif,
1988;Zhangetal., 1990;Wangetal., 2001).
e Hetao Basin is a Cenozoic faulted basin located among the
Ordos Block, Alxa Block, and Yinshan-Yanshan Orogen, bounded
by well-developed faults (Figure1). From west to east, the northern
boundary faults of the basin are the Langshan Piedmont Fault
(LPF), Sertengshan Piedmont Fault (SPF), Wulashan Northern
Fault (WNF), Wulashan Piedmont Fault (WPF), and Daqingshan
Piedmont Fault (DPF). e Ordos Northern Fault (ONF) and
Horiger Fault (HF) represent the southern and Eastern boundaries
of the Hetao Basin, respectively. Aected by the NE expansion of
the Tibetan Plateau and the subduction of the Pacic Plate, these
faults had intense activity in the Quaternary, especially the northern
boundary faults, which caused a series of strong earthquakes,
instancing historical M= 8.0 earthquake occurred in 849A.D.
(Ranetal., 2003a;Heetal., 2007;Nieetal., 2010;Nie, 2013;He and
Ma, 2015;Raoetal., 2019;Suetal., 2021) (Figure1). Future large
earthquakes potentially threaten the area controlled by the northern
boundary faults.
Over the last 40 years, scholars have extensively studied the
characteristics of the Late Quaternary activity, vigorous earthquake
activity, and seismic risk of those northern boundary faults, which
provide insights into active structures and recurrence patterns
of local strong earthquakes along active faults (Maetal., 1998;
Maetal., 2000;Dengetal., 1999;Jiangetal., 2001;Ranetal.,
2002,2003b;Yangetal., 2002;Yangetal., 2003;Nieetal., 2011;
Raoetal., 2016;Raoetal., 2019;Liangetal., 2019;Heetal., 2020).
More recent results showed that the LPF-SPF experienced seven
paleoearthquakes during the Holocene, with a recurrence period
of 1.37 ± 0.11 ka and an earthquake risk of M> 8.0 (Dong, 2016;
Dong, 2016;Liangetal., 2021;Ma and Dong, 2024). e fourteen
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Wei etal. 10.3389/feart.2024.1437012
paleoearthquake events occurred during the Holocene in the DPF,
including the 849A.D. earthquake (Lietal., 2015;Yuanetal., 2023).
Similarly, the WPF has experienced six paleoearthquakes during
the Holocene (Li, 2014). However, research on the geometry
and kinematics behaviors of the WNF is lacking. e Wulashan
Piedmont Fault is the boundary fault of the secondary Sag within
the Hetao Basin, located between the LPF-SPF and DPF. Obtaining
information about the shallow structural characteristics and the Late
Quaternary activity of the WNF may provide for the overall study of
the structural characteristics and seismic risk of the Hetao Basin as
well as an essential scientic basis for urban and rural construction
and land resource planning in the Hetao Basin.
As the boundary between Wulashan and the Hetao Basin,
and the boundary of a stratum from the view of geomorphology
and stratigraphy, separately, the WNF was inferred to be on
the northern foot of Wulashan (Guo et al., 1980). However, no
denitive proof exists, such as fault clis, triangular facets, fault
scarps, or fault gouges. Owing to serious desertication and buried
structural traces along the WNF, there is no systematic mapping and
exploration work along the WNF, and more extensive information
could be obtained. Current knowledge about this fault’s distribution
and the Quaternary activity mainly depends on understanding
the relationship between the schistositized zone of the fault
stretching west of Xiaoshanzui and overlying Quaternary ood-
slope sediment. Some Chinese scholars argued that the activity of
WNF has been weak since 66.78 ±5.14ka B.P. (Chen, 2002;Heetal.,
2019). However, it remains uncertain the geometry of the fault
and when the latest activity occurred. erefore, it is necessary
to use relevant methods of active fault exploration to conduct
further research on the shallow structural characteristics and Late
Quaternary activity of the WNF.
e research methods for studying the Quaternary activity
of inferred or buried faults are becoming more advanced. e
most commonly used and practical detection approach is based
on combining the three methods of shallow articial seismic
exploration, drilling exploration, and the study of the stratigraphic
age. Generally, the location of faults, burial depth of the upper
breakpoints, and shallow structural morphology are obtained
using shallow seismic exploration methods (Heetal., 2001;
Yangetal., 2004;Liuetal., 2008;Liuetal., 2009;Fangetal., 2015).
Subsequently, the location of the fault and burial depth of the upper
fault point are further determined by a combination of drilling
and prole and stratigraphic age analyses. In addition, the latest
active ages, dislocation quantities, and slip rates of the faults can be
simultaneously analyzed (Xiang etal., 2003;Xuetal., 2000;Lei etal.,
2008;Lei etal., 2011a;Ezquerroetal., 2015). In this study, we aimed
to analyze the shallow structural morphology and Late Quaternary
activity parameters of the WNF by using a combination of shallow
seismic exploration and drilling joint prole detection.
2 Geological background
e east-trending Hetao Basin is located along the northern
margin of the Ordos Block. It extends from 40 to 80km from
north to south and ∼440km from east to west. Controlled by
the northern boundary faults, including Langshan Piedmont
Fault (LPF) -Sertengshan Piedmont Fault (SPF), and Wulashan
Northern Fault (WNF), Wulashan Piedmont Fault (WPF),
and Daqingshan Piedmont Fault (DPF), the Hetao Basin is
divided into three sags including Linhe Sag, Baiyanhua Sag, and
Huhe Sag from west to east. ese sags are right-step echelon
arranged and dustpan-shaped, deep in the north and shallow
in the south, well preserving thick Quaternary sedimentation
(eResearchGrouponActiveFaultSystemaroundOrdosMassif,
1988). According to drilling and petroleum geological proles, the
Linhe Sag in the western part of the Hetao Basin is the deepest
Cenozoic basin in the Ordos Block, with a maximum thickness of
2,400m in Quaternary (Figure2) (Ranetal., 2003b). e prominent
upli in the basin is the Wulashan Horst.
e Cenozoic Strata of the Linhe Sag is mainly composed of
the Pliocene, Middle Pleistocene, Upper Pleistocene, and Holocene
sediment. e lithological characteristics of dierent periods are as
follows:1) e Pliocene Series consist of purple-red and brick-red
sandy clay rock; 2)e Middle Pleistocene is mainly composed of
blue-gray sub-sandy soil and grayish-black muddy clay; and 3)e
Upper Pleistocene mainly consists of a sedimentary combination of
gray, yellow-green silt, ne sand, gray-brown silt mixed with gravel,
clay, silt, and sandy-clay, with the lower part being lacustrine facies
and the upper part being alluvial lacustrine facies. e Holocene
series is composed of light greyish-yellow gravel, breccia, and
sandy soil containing breccia, mainlyconsisting of alluvial–proluvial
deposits with relatively coarse particles (Li, 2006;Fanetal., 2011;
Liuetal., 2014;Bietal., 2021). e thickness of the Quaternary in
the region ranges from 400 to 2,000m and the thinnest point is
located near Xiaoshanzui, Wulateqianqi County, with a thickness
of ∼400m (eResearchGrouponActiveFaultSystemaround
OrdosMassif, 1988).
e Wulashan Horst is an E-W tectonic upli controlled by the
WNF and WPF. It is about 120km long and 15–20km wide in the
east, narrowing westward,and pinching out at Wulateqianqi County.
e activity of the WPF on the southern foot is more potent than that
on the northern foot. Tectonic upli is asymmetric in the Wulashan,
and higher at the southern ank (Heetal., 2019;Shietal., 2021).
e tectonic landforms, such as fault clis, fault triangles, and fault
scarps, are clear and prominent in scale and spread continuously
in front of the southern foot. In contrast, the fault clis and fault
triangles on the northern foot are blurred because of the weaker
activity of WNF (eResearchGrouponActiveFaultSystemaround
OrdosMassif, 1988).
e WNF, taken as the boundary fault of the Wulashan Horst
and Linhe Sag, plays a vital role in the seismic risk analysis of
the Hetao Basin. Destructive earthquakes near the fault include
the 849A.D M= 8.0 and the 1996 Baotou M= 6.4 earthquakes
(Heetal., 2020). is WNF is a normal fault about 75km long and
has a northeast–east strike, northward dip, and dip angle of ∼80°.
It extends from Xiaoshanzui village in the Wulateqianqi County in
the west to Shadegai village northwest of Baotou City in the east.
It can be divided into western and eastern segments bounded by
the Miligeng village according to the geomorphologic trace of the
fault. e western segment’s linear trace between horst and sag is
evident from the remote sensing images but blurred in the eastern
segment (Figure2). From the geological map, the sag controlled by
the eastern segment is less than 10km wide and comprises scattered
residual mountains of bedrock. Its surface is mainly covered by
deserts without notable fault scarps and a clear structural trace in
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Wei etal. 10.3389/feart.2024.1437012
FIGURE 2
Seismic and geological map of the study area (See Figure1 for location). Strata from (Zhu, 1964), Quaternary sedimentary isopaches from (Ranetal.,
2003b), and epicenter of earthquakes M= 8.0 and M= 6.4 from (Heetal., 2020).
Quaternary (Chen, 2002). e WNF is located in a piedmont alluvial
plain area, the sedimentary facies are mainly alluvial-lacustrine.
Although the sediment particles are coarse and poorly sorted, their
stratication characteristics are distinct.
3 Materials and methods
3.1 Shallow seismic survey lines
Shallow seismic exploration is a geophysical method that
utilizes dierences in the elasticity and density of subsurface
media to infer the nature and shape of subsurface rock layers
by observing and analyzing the response of Earth to articially
generated seismic waves. is method can be used to detect and
study the geological structure of shallow crust (Zhaoetal., 2011;
Yangetal., 2016). Shallow seismic exploration includes two basic
methods: the refraction and reection wave methods (Dengetal.,
2003). e reection seismic exploration method can be utilized to
obtain records with a high signal-to-noise ratio and high resolution
because of “small path distance, small gun distance, high coverage
times” acquisition technology and high-precision data processing.
erefore, buried faults, cavities, and nonuniform anomalies can be
eectively detected with the reection seismic exploration method
(Heetal., 2001). At present, reection seismic methods are widely
used to detect the location, nature, and activity of the active faults
with upper fault points buried more than ten to hundreds of
meters deep in Quaternary overlying areas in Chinese cities, such as
Fuzhou City, the capital of the Fujian Province, and Yinchuan City,
the capital of the Ningxia Autonomous Region (Zhuetal., 2005;
Chaietal., 2006;Lietal., 2017).
In this study, the location and shallow structural characteristics
of the WNF were analyzed using shallow reection seismic
exploration. In October 2021, two shallow seismic survey lines
crossing this fault named L1 and L2 were established (Figure3A).
e L1 seismic line was laid on a desert road northeast of
Mostingamu village (northwest to southeast, 3.15km long). e
L2 seismic line was established on a desert road ∼6km east of L1
(southeast to northwest, 4.66km long).
For shallow seismic exploration, 508 XT digital seismographs
were used to collect eld data (Figure4A), and a P26-TYPE
VIBROSEIS was employed to trigger seismic waves (Figure4B). e
basic parameters were as follows: frequency range of 20–120Hz and
scan length of 16s. e observation system consisted of a channel
spacing of 2 or 3m, gun spacing of 10 or 15m, and 600 or 700
channels of internal excitation and bilateral asymmetric reception.
e sampling interval was 1ms. e duration of each record was 2s.
3.2 Composite drilling of geological
sections
Composite drilling of geological sections is generally performed
based on shallow seismic exploration. e drill holes were located
on both sides of the fault, where geophysics indicated a clear
vertical displacement. When the geophysical survey showed that
the main fault was divided into several branches, composite drilling
geological sections were established across the branch fault. e
shallowest burial depth was the upper fault point. e borehole
line coincided with, or nearly coincided with, the shallow seismic
survey line and intersected the fault strike vertically or at a large
angle. e drilling sequence was carried out mainly referred to the
principle of the folding method, which is a construction method
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Wei etal. 10.3389/feart.2024.1437012
FIGURE 3
Locations of conducted shallow seismic survey lines and composite drilling of geological sections (See Figure2 for location). (A) Locations of shallow
seismic survey lines L1 and L2. (B) Location of the MSTS boreholes. (C) Location of the MSTN boreholes.
FIGURE 4
Equipment and total core recovery. (A) The 508 XT Digital Seismograph. (B) P26-TYPE VIBROSEIS. (C) Total station. (D) Core recovery percentage of
MSTN sections.
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Wei etal. 10.3389/feart.2024.1437012
of folding from the outside to the inside, gradually approaching
the fault, emphasizing the dynamic construction and analysis, and
continuous exclusion and determination to gradually dene the
location of the fault. Figure3C represents the classical method of
the folding method. Specic operation steps of this method are
as follows: 1) Taking vertical projection position on the ground
of the upper breakpoint Fp2 obtained by shallow articial seismic
exploration as the datum point, drill boreholes NZK1 and NZK2 at
both ends of the drilling section to make sure the fault is between
the two boreholes; 2) Drill the third borehole NZK3 at the middle
of the two boreholes. According to the drilling results of NZK1,
NZK2, and NZK3, it is concluded that the fault lies between the
drilling holes of NZK1 and NZK3; 3) Continue to drill borehole
ZK4 at the middle of ZK1 and ZK3. By repeating a similar practice,
boreholes ZK5 and ZK6 are constructed respectively to constrain
progressively the accurate fault Fp2a and Fp2b (Leietal., 2011a).
Several application cases show that the method can determine
precisely the location of buried active fault (Leietal., 2011b;
Leietal., 2014;Caoetal., 2015;Shenetal., 2022).
To further study the surface structure and active parameters of
the WNF, such as the buried depth of the upper fault point and
coseismic dislocation, two composite drilling geological sections
were established in October 2022 based on the results of the shallow
articial seismic exploration and eld survey as well as the position
of the upper breakpoint of faults Fp1 and Fp2 explained by the
L1 line survey using the folding method: the Mostingamu North
Section (MSTN) and Mostingamu South Section (MSTS). e two
sections crossed the fault and nearly coincided with the L1 shallow
seismic reection section (Figure3A). Six boreholes were drilled
in the MSTS; that is, SZK2, SZK4, SZK3, SZK5, SZK6, and SZK1
from south to north, with a borehole spacing of 25, 25, 25, 12.5,
and 12.5m, respectively (Figure3B). e depths of the single holes
were 41.5, 42, 41, 48, 41, and 42.6m, respectively, with 256.1m
cumulative footage. Six boreholes were drilled in the MSTN; that
is, NZK2, NZK3, NZK5, NZK4, NZK6, and NZK1 from south to
north, with a borehole spacing of 50, 12.5, 12.5, 12.5, and 12.5m,
respectively (Figure3C). e depths of the single holes were 43,
41, 43.5, 41, 42, and 43.6m, respectively, with 254.1m cumulative
footage. Before analyzing the fault nature and fault characteristics
of the same stratum, the relative elevation of the boreholes at the
two sites was separately corrected by the total station (Figure4C).
e topography of the two combined geological sections was high
in the south and low in the north. e vertical dislocation between
holes SZK1 and SZK2 in the MSTS was 2.0m. e height dierence
between boreholes NZK1 and NZK2 in the MSTN is 1.96m. In
addition, the back footage was controlled within 1–2m and the core
recovery percentage was greater than 95% (Figure4D).
3.3 Sampling and testing of the
stratigraphic age
Optically Stimulated Luminescence (OSL) dating is one of
the most popular and accepted dating techniques in Quaternary
research. e main dating materials are quartz and feldspar. e
test particle sizes are generally divided into coarse, medium,
and ne. e dating ranges from decades to 100,000 and
more than 700,000years (Huntley and Prescott, 2001;Liuetal.,
2011;Laietal., 2013). is technique has been widely used for
sediment samples from loess, deserts, lakes, rivers, and glaciers
(Fanetal., 2013;Luetal., 2016;Wangetal., 2017;Weietal., 2018;
Zengetal., 2019;Ouetal., 2021). e lithology of the samples
collected in this study was mainly alluvial–alluvial sub-clay and
alluvial–lacustrine clay. OSL dating was used to determine the
absolute stratigraphic ages of the samples.
e latest activity of the fault occurred aer that of the top of
the latest strata deformed by the fault and before that of the bottom
of overlying unfaulted strata in the combined borehole geological
section. ree and two OSL dating samples were collected from
the MSTS and MSTN, respectively. e lithologies of the samples
mainly consist of sandy sub-clays. e collection of samples was
synchronized with the collection of the drilling core and all samples
were packaged in a light-proof manner.
Sample tests were conducted at the Shandong Seismological
Engineering Research Institute. e tests comprised four steps:
pretreatment, equivalent dose test, environmental dose rate test, and
data analysis (Luetal., 2007). e pretreatment was performed in
a dark laboratory room with a light-emitting diode light source of
661 ± 15mm. All samples were uncontaminated and unexposed
at the center of the package. During pretreatment, 30% hydrogen
peroxide (H2O2) and 30% hydrochloric acid (HCl) were added
successively to remove organic matter and carbonates from the
sample. Subsequently, feldspar and α-irradiated quartz surfaces
were removed using40% hydrouoric acid (HF) etching for 40min,
followed by treatment with 10% HCl to remove uoride, ensuring
that no feldspar minerals were present in the sample. e equivalent
dose of all samples was measured using a Danish Risoe DA-20-C/D
ermoluminescence/Luminescence automatic measuring system
and single-aliquot regenerative dose (Murry and Wintle, 2000;
Murry and Wintle, 2003). e contributions of U, , and K, and
their decay to the environmental dose rate were measured using
a plasma mass spectrometer and full-spectrum plasma emission
spectrometer. e eects of the moisture content and cosmic rays
were considered. e sample age was equal to the equivalent dose
divided by the environmental dose rate (Table1).
4 Results
4.1 Shallow seismic reection prole
section and interpretation
4.1.1 Shallow seismic prole characteristics of
survey line L1
Post-stack migration time and depth-section interpretations
of line L1 are shown in Figure5. e reection time prole
indicates multiple relatively continuous reected wave events with
a two-way travel time above 600ms. According to the wave
group characteristics of the reection time section, three formation
reection interfaces were identied in the section, which were
marked as T1, T2, and T3. e reection energies of reected wave
events T1 and T2 are strong and continuous reection information
can be observed. South of the stake number of 5,025m and a two-
way travel time shallower than 350ms, the reected wave event T3
is faintly visible and can be tracked continuously. North of stake
number 5,025m and two-way travel time 400ms deep, the reected
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TABLE 1 OSL dating results for the MSTS and MSTN.
Drilling
geological
section
No. Buried
depth (m)
Sampling
horizon
U (ppm) Th (ppm) K (%) Water
content (%)
Environmental
Dose rate
(Gy/ka)
Equivalent
Dose (Gy)
Age (ka)
MSTN ZK5 34.4 Bottom of stratum
5
1.9 8.4 2.3 24.7 4.4 ± 0.2 225.5 ± 9.5 73.8 ± 2.8
MSTN ZK3 36 Top of stratum 2 1.5 9.9 2.0 17.9 3.5 ± 0.3 288.9 ± 11.3 91.2 ± 4.4
MSTS ZK6 25.2 Top of stratum 4 1.3 7.9 2.3 31.4 2.7 ± 0.2 55.5 ± 10 19.6 ± 3.5
MSTS ZK6 27.7 Middle of stratum
4
0.9 4.2 2.5 20.4 2.7 ± 0.3 115.5 ± 5.5 40.8 ± 2.5
MSTS ZK6 34.4 Bottom of stratum
3
0.8 4.4 3.1 20.1 3.3 ± 0.2 196.5 ± 20.5 59.1 ± 6.2
energy was extremely weak, and the reected information of event
T3 was almost invisible. e stratigraphic interface revealed by the
seismic prole generally exhibits a shallow distribution shape in
the south and is deep in the north. T2 strata are in unconformable
contact with the overlying T1 strata.
Based on the transverse continuity characteristicsof the reected
wave group, three secondary faults were interpreted in the section,
which were marked as faults of Fp1, Fp1.1, and Fp2, respectively.
e parameters for each breakpoint are listed in Table2. e fault
Fp1 is a normal fault with a northerly dip. e distinguishable upper
breakpoint of the fault is located at stake number 5,470m on the
survey line and the buried depth is ∼165m. e fault Fp1.1 is a
normal fault. e distinguishableupper breakpoint is located at stake
number 5,230m of the survey line, with a buried depth of ∼155m,
forming an inverted Y-shape with fault Fp1. Fault Fp2 is a normal
fault that dips to the north; the distinguishable upper breakpoint is
located at survey line stake number 5,005m and the buried depth is
∼120m.
4.1.2 Shallow seismic prole characteristics of
survey line L2
Post-stack migration time and depth-section interpretations
of the line L1 are shown in Figure6. e reection time prole
indicates multiple relatively continuous reected wave events with
a two-way travel time above 600ms. According to the wave
group characteristics of the reection time section, four formation
reection interfaces were identied in this section, marked as T1,
T2, T3 and T4, respectively. e reection energies of reected
wave events T1, T2, and T3 are strong, and continuous reection
information can be observed. South of stake number 4,700m,
the reected wave event T3 is faintly visible and can be tracked
continuously. North of stake number 4,700m, a data two-way
travel time shallower than 30ms, an exploration blind spot without
eective reection information was detected. e stratigraphic
interface revealed by the seismic prole generally presents a
distribution that is shallow in the south and deep in the north.
e T2 and T4 strata are in unconformity contact with the
overlying T1 strata.
Based on the shallow seismic prole, the reection energy of
reected wave events T2, T3, and T4 is relatively strong, with a
continuous transverse direction. According to the phenomena of
folds and dislocations in the reected wave event, a total of three
faults were identied in the section and marked as faults of Fp3,
Fp3.1, and Fp4, respectively. e parameters for each breakpoint
are listed in Table3. e fault Fp3 staggers the bottom interface of
T1, which is a normal fault. e apparent dip is northward. e
distinguishable upper breakpoint was located at survey line stake
number 2,450m, with a buried depth of ∼55m. e fault Fp3.1
is a reverse normal fault on the hanging wall of fault Fp3. e
fault extends upward without breaking the T4 stratum interface.
e distinguishable upper breakpoint was located at stake number
2,750m on the survey line and the buried depth was ∼115m. e
fault Fp4 staggers the T4 formation interface, extends upwards,
and terminates at the lower part of the T1 bottom interface. e
fault Fp4 is a normal fault with an apparent northward dip. e
distinguishable upper breakpoint is located at stake number 3,235m
on the survey line and the buried depth was ∼104m.
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FIGURE 5
The uninterpreted and interpreted results for the L1 shallow seismic exploration prole and the layout of the boreholes. (A) Uninterpreted post-stack
migration time-section. (B) Interpreted post-stack migration time-section and the distribution map of boreholes. (C) Depth-section interpretation.
TABLE 2 Fault parameters based on the seismic reection proles of L1 and L2.
No. Breakpoint Breakpoint Position(m) Tendency Buried depth (m) Break distance (m)
L1
Fp1 5,470 N 165 5–8
Fp1.1 5,230 S 155 2–4
Fp2 5,005 N 120 4–7
L2
Fp3 2,450 N 55 2–4
Fp3.1 2,750 S 115 2–4
Fp4 3,235 N 104 3–5
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FIGURE 6
The uninterpreted and interpreted results for the L2 shallow seismic exploration prole. (A) Uninterpreted post-stack migration time-section (B)
Interpreted post-stack migration time-section. (C) Depth-section interpretation.
Based on the comprehensive analysis of the shallow seismic
exploration results of the L1 and L2 survey lines, two new faults F1
and F2 have been discovered in the northern area of Wulashan. e
line connecting breakpoint Fp1 of L1 and breakpoint Fp3 of L2 is F1,
and the other line connecting breakpoint Fp2 of L1 and breakpoint
Fp4 of L2 is F2. Both are considered to reect the WNF.
4.2 Geological prole detection and
interpretation
e MSTS and MSTN were arranged separately across the Fp1
of F1 and Fp2 of F2 breakpoints of the WNF. eir positions in the
L1 shallow seismic exploration section are shown in Figures3,5B.
4.2.1 Geological prole of MSTS
Based on the lithology, color, material composition, bedding
structure, and other characteristics of the drilled core strata, the
borehole of the MSTS section can be divided into 11 natural
sublayers from bottom to top. Based on OSL dating (Table1) and
regional stratigraphy, the section can be divided into three sets
of strata: Holocene (Qh), Upper Pleistocene (Qp3), and Pliocene
(N2). e lithological characteristics of each layer are described
in Table3.
In the MSTS section, faults were identied in multiple strata.
Our results show that strata ①,②, and ③underwent dierent
degrees of structural deformation, but the top interface of stratum
④was not aected by faults. Strata ②and ③have a stable
sedimentary thickness on both sides of the fault and their lithological
characteristics signicantly dier from those in the upper and lower
layers, which can be used as the marker strata of fault dislocation
(Figure7A). According to the fault relationship of the strata in the
same horizon, one stepped normal fault was identied, that is fault
Fp1a, dipping north (Figure8). e characteristics of the dislocation
relationship between each marker layer and the fault are described
in detail below.
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TABLE 3 Lithological characteristics of the MSTS section.
No. Lithology Geological Description Age
⑪Loam grayish-yellow, containing a small amount of sharp-edged gravel, with a particle size ranging from 0.2 to 0.4cm, with poor sorting and
loose structure
Qhdl
⑩Coarse sand yellow-brown, mixed with granite gravel, with a particle size ranging from 0.2cm to 1.0cm, with sharp edges and corners, with poor
sorting and loose structure
Qhdl
⑨Loam brownish-yellow, containing blue-gray and o-white granite gravel, with a particle size ranging from 0.2 to 1.5cm, occasionally large
breccias with a particle size of 3cm, with sharp edges and corners, with poor sorting and loose structure
Qhdl
⑧Loam light brown-yellow, occasionally blue-gray and o-white and light esh-red granite gravel, particle size is concentratedat0.2–0.4cm,
occasionally clay cemented agglomerates, with poor sorting
Qhdl
⑦Sandy Loam light yellow-brown sandy sub-clay, containing eshy red, gray-black, and gray granite gravels, with a particle size ranging from 0.2 to
1.0cm, with sharp edges and corners and poor sorting, partially sandwiched with thin layers of black clay, with horizontal bedding
Qp3l-apl
⑥Sandy Loam yellowish-brown and brown with strong sandy feeling, occasionally blue gray and gray black gravel, particle size ranges from 0.2 to
3.0cm, with sharp edges and corners and poor sorting
Qp3l-apl
⑤Sandy Loam brown-yellow, occasionally sandy glue agglomerates, containing ∼10% light brick-red and gray-black granite gravel with, with sharp
edges and corners, poor sorting
Qp3l-apl
④Sandy Loam yellowish-brown, relatively loose, partially granulated, containing gray and o-white granite gravel, with sharp edges and corners,
particle size concentrated at 0.2–4.0cm, with poor sorting
Qp3l-apl
③Sandy Loam brown-yellow, relatively loose, partially cemented block, can be crushed by hand, containing small particle size blue ash, light
brick-red granite debris
Qp3l-apl
②Silt Fine Sand earthy yellow, slightly yellowish green, partially containing light brick-red and blue gray granite debris Qp3l-apl
①Clay Stone light brick-red, medium weathering, mixed with a large amount of gray-green and light brick-red granite gravel, poorly rounded,
particle size concentrated at 0.2–1.0cm, with poor sorting
N2
FIGURE 7
Symbolic strata of fault dislocation at the two composite drilling geological sections. (A) Lithology characteristics of mark stratum ②and ③of MSTS. (B)
Lithology characteristics of mark stratum ②,③,④and ⑤of MSTN.
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FIGURE 8
Composite drilling geological section for MSTS.
e normal fault of Fp1a was identied between boreholes ZK6
and ZK1. e formation characteristics of Fp1a are as follows: e
top-bottom interface of the marker stratum ②has a notable drop
on both sides of the fault Fp1a. It is characterized by a fault with
thick hanging and thin footwalls. e vertical oset at the bottom
interface of this layer is 1.5m. Marker stratum ③is brownish-
yellow sandy loam, buried at a depth ranging from 33.5–36m. e
bottom interface is dislocated by the Fp1a fault between boreholes
ZK6 and ZK1, with a vertical oset of 0.9m. e top interface of
marker stratum ③is not aected by the fault and can be used as the
uppermost point of the Fp1a fault, with a buried depth of ∼30m.
According to the OSL dating results of the Upper Pleistocene in
the MSTS section, the stratigraphic ages at depths of 25.2, 27.7, and
34.4m are 19.6 ± 3.5ka B.P., 40.8 ± 2.5ka B.P., and 59.1 ± 6.2ka
B.P., respectively. Based on these above-mentioned results, the latest
activity of fault Fp1a on the F1 occurred before 40.8 ± 2.5ka B.P.
4.2.2 Geological prole of MSTN
Based on the lithology, color, material composition, bedding
structure, and other characteristics of drilled core strata, the
borehole of the MSTN section was divided into 11 natural sublayers
from bottom to top. Based on OSL dating results (Table1) and
regional stratigraphy, the section can be divided into three sets of
strata: Holocene (Qh), Upper Pleistocene (Qp3), and Pliocene (N2).
e lithological characteristics of each layer are listed in Table4.
Results for the MSTN section show that strata ①to ④have
faults or absences in the same layers. Strata ②and ③have a stable
sedimentary thickness and notable lithological characteristics on
both sides of the fault, which can be used as the symbolic strata
for fault dislocation. Stratum ①is a typical ridge accumulation
that can be used as a fault identication marker. Stratum ⑤is
clay, which had a relatively stable depositional environment and
was deposited continuously in the ve boreholes. e bottom
was less deformed by the fault and can be used as a marker
stratum for strata overlying the fault (Figure7B). Based on the fault
characteristics and overlying relationship of the marker layer, two
stepped normal faults dipping north were identied in this section,
that is, Fp2a and Fp2b (Figure9). Dislocated marker strata are
described in detail below.
e normal fault of Fp2a was identied between boreholes ZK3
and ZK5. e formation characteristics of Fp2a are as follows: Marker
stratum ②is dark gray clay. Aected by Fp2a, the layer was faulted at
the bottom interface between boreholes ZK3 and ZK5, resulting in a
vertical fault distance of 0.94m. Marker stratum ③is reddish-brown
clay with a vertical fault distance of 0.98m at the bottom interface on
both sides of Fp2a. e marker stratum ④mainly contains brown-
yellowand yellow-green silt,which is only visible in the hanging wall of
Fp2a and absent in the footwall. It can be assumed that the upper wall
layer ④is the deposit in front of the ridge formed by the fault scarp.
Marker stratum ⑤is yellow-green clay. e top interface of this layer
has large undulations and an uneven deposition thickness, which are
presumed to have been scoured. e bottom interface of this layer was
close to the at and was not aected by Fp2a. erefore, the bottom
interface of layer ve can be the uppermost point of fault Fp2a, with a
buried depth of ∼34.2m.
e normal fault of Fp2b was identied between boreholes ZK6
and ZK1. e formation characteristics of Fp2b are as follows: Marker
stratum ②on both sides of fault Fp2b shows that the thickness of
the hanging wall is larger than that of the footwall, representing
characteristics of a contemporaneous fault, with a 1.15m oset in
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TABLE 4 Lithological characteristics of the MSTN section.
No. Lithology Geological Description Age
⑪Sandy Loam yellow-brown, relatively loose, containing a small amount of light eshy red granite gravel, with a particle size ranging from 2 to
6cm, with sharp edges and corners, partially containing thin sandwiched yellowish-brown sub-clay
Qhdl
⑩Loam yellowish-brown and brown, relatively loose, containing blue-gray and o-white granite gravel, with a particle size ranging from 1
to 4cm, occasionally large breccias with a particle size of 7cm, with sharp edges and corners, occasionally with white hyphae
Qhdl
⑨Sandy Loam yellow-brown, containing a small amount of blue-gray and o-white and light esh-red granite gravel, with a particle size ranging
from 2 to 6cm, with sharp edges and corners
Qhdl
⑧Loam yellowish-brown and brown sub-clay, relatively loose, containing o-white and light esh-red granite gravel, with a particle size
concentration at 4–6cm, with sharp edges and corners, partially sandwiched with thin layers of yellowish-brown sandy sub-clay
sand, white hyphae can occasionally be observed
Qhdl
⑦Loam yellowish-brown, occasionally containing o-white and light eshy red granite gravel, with a particle size ranging from 1 to 4cm,
thin layer of reddish-brown ne sand can occasionally be seen, partially sandwiched with a thin layer of reddish-brown clay and
yellow-green, with a small amount of gray-green and brown stripes
Qp3l-apl
⑥Fine sand yellowish-brown and brown, containing a small amount of light eshy red granite gravel, with a particle size concentration of
4–7cm in, occasionally large breccias with a particle size reaching up to10cm, partially sandwiched with yellowish-brown loam
and reddish-brown coarse sand
Qp3l-apl
⑤Clay yellow-green, partially mixed with thin layers of blue-gray, gray-green, and rust-yellow clay, occasionally containing rust-yellow
streaks, with clear horizontal bedding
Qp3l-apl
④Silt Sand brown-yellow and yellow-green, containing a small amount of cemented sandstone blocks, thin layer of brown-yellow clay on the
top with very few rust-yellow and gray-green stripes, lower part is brown-yellow, yellow-green silt
Qp3l-apl
③Clay reddish-brown clay, occasionally with yellow streaks Qp3l-apl
②Clay dark gray with a small amount of gray-blackiron-manganese spots, clear horizontal bedding Qp3l-apl
①Sandy Clay Stone purple-red and hard, with a small number of gray-green stripes and a small amount of white spots N2
FIGURE 9
Composite drilling geological section for MSTN.
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the bottom interface. Marker stratum ③was not deformed by Fp2b.
Its bottom interface can be the uppermost point of fault Fp2b, with a
buried depth of ∼36.3m.
According to the OSL dating results, the geological age of the
bottom interface of stratum⑤is 73.8 ± 2.8ka B.P. and that of the top
interface of stratum ②is 91.2 ± 4.4ka B.P. Based on these above-
mentioned results, the latest activities of normal faults Fp2a and
Fp2b on the F2 occurred before 73.8 ± 2. 8ka B.P. and 91.2 ± 4.4ka
B.P., respectively.
5 Discussion
Based on the results of this detection, the WNF is not a single
surface fault but rather multiple branches consisting of F0, F1, and
F2. Near the surface, the three faults spread in a divergent manner
to the inner terraces of the basin (Figure3A). Faults F1 and F2 are
newly conrmed late Pleistocene faults. Fault F0 must be identied
from the seismic reection proles due to the bedrock area’s lack
of reection wave groups. It is considered a pre-quaternary fault
because it lacks relevant evidence of Quaternary activity.
(1) e WNF formed during the Mesozoic stage. Since
the Cenozoic, the WNF has been characterized by
vigorous vertical dierential activity and intermittent
activity, with the north wall descending and the south
wall upliing, forming an E-W trending normal slip
fault zone (eResearchGrouponActiveFaultSystem
aroundOrdosMassif, 1988). In the Neogene, faults F0 and F1
dipping north and the secondary fault of Fp1.1 dipping south
developed at the northern foot of Wulashan (Figure10A).
Since the Quaternary, the WNF has inherited activity. In the
early and middle periods of the Late Pleistocene, a new fault of
F2 developed on the northern side of F1. In the late period of
the Late Pleistocene, F1 was reactivated. In the Holocene, the
F1 and F2 faults were covered and turned into buried faults
(Figure10B). From the long-time scale of fault evolution, the
activity of the WNF is characterized by migrating basin-ward
into the hanging wall with time, which is consistent with the
evolution model proposed by Dartetal. (1995).
(2) e section of MSTS crossing Fp1 on the F1 reveals one
fault Fp1a with two seismic events. e latest event occurred
before 40.8 ± 2.5ka B.P., with a 0.9m maximum coseismic
dislocation. e older event occurred before 59.1 ± 6.2ka
B.P., with a 0.6m maximum coseismic dislocation. e 1.5m
dislocation of the bottom interface of marker stratum ②
was the cumulative dislocation of the two events. According
to the empirical equation for magnitude and coseismic
dislocation (Slemmons, 1982), considering the maximum
coseismic dislocation of 0.9m, the maximum magnitude of
an earthquake on F1 can be estimated to be M= 6.63 ± 0.4,
which could be the maximum probable earthquake under the
condition of F1 rupture alone.
e section of MSTN crossing the branch fault Fp2 on the
F2 reveals two faults Fp2a and Fp2b, with two seismic events.
e latest event was the activity of Fp2a faulting simultaneously
the bottom surface of maker marker stratum ②and ③0.94 and
0.98m. Taking the drilling error into account, the displacement
of this event is 0.96m (average of 0.94 and 0.98m). According
to the empirical equation for magnitude and coseismic dislocation
(Slemmons, 1982), the maximum magnitude of an earthquake on
Fp2a can be estimated to be M= 6.65 ± 0.4. e older event was the
activity of Fp2b faulting the bottom surface of maker marker stratum
②1.15m. According to the empirical equation for magnitude and
coseismic dislocation (Slemmons, 1982), the maximum magnitude
of an earthquake on Fp2b can be estimated to be M= 6.71 ± 0.4. If
the F2 rupture alone, the maximum probable earthquake is between
M= 6.65 ± 0.4 and M= 6.71 ± 0.4.
Suppose a full-length rupture of the WNF, the scale of the
fault zone is also an important factor aecting the magnitude of
the earthquake. According to the empirical equation for magnitude
and length (Well and Coppersmith, 1994), the maximum possible
magnitude of an earthquake related to this fault zone can be
estimated to be M= 7.3 ± 0.34. However, considering estimate errors
and given that the latest activity of the WNF occurred during the late
stage of the Late Pleistocene, the maximum magnitude of a potential
earthquake is determined to be M= 6.5–7.0.
is passage enriches the research on the Quaternary activity of
boundary faults in the Hetao Basin. Summing up briey the previous
achievements: 1) e vertical activity rate of the Langshan Piedmont
Fault was 1.12mm/yr since the Holocene (Sunetal., 2021); 2) e
average vertical slip rate of the Sertengshan Piedmont Fault since
65ka was 1.8–3.2mm/a (Liangetal., 2019); 3) the vertical slip
rates of the Daqingshan Piedmont Fault were 2.5–3.88mm/a and
1.78–2.83mm/a since 58 and 11ka (Xuetal., 2022); 4) the vertical
slip rate of Wulashan Piedmont Fault were 2.20–2.28mm/a and
1.12–1.34mm/a since 65ka and Holocene (Heetal., 2020); 5) the
latest activities of the WNF were 47.08 ± 3.7–73.8 ± 2.8ka B.P. and
the maximum vertical dislocation were 0.9–1.15m; 6) the coseismic
vertical displacement of the Ordos Northern Fault was 2–2.5m, and
the latest activity occurred 43.5–70ka B.P. (Liuetal., 2022); 7) the
activity of the Horiger Fault had tended to be stable since late of the
Late Pleistocene (Hao, 2017). In other words, the Late Quaternary
activity of the Langshan Piedmont Fault, Sertengshan Piedmont
Fault, Daqingshan Piedmont Fault, and Wulashan Piedmont Fault
are the most active. According to related studies, the maximum
possible magnitude of the earthquake in the Langshan Piedmont
Fault - Sertengshan Piedmont Fault is 8.1 (Liangetal., 2021). e
Daqingshan Piedmont Fault has the highest probability of producing
an earthquake with a magnitude of 7.0 or 7.5 in the next 100years
and the Wulashan Piedmont Fault is more likely to produce an
earthquake with a magnitude 7.0 or more signicant in the next
hundred years (Pan, 2021). It suggests that future earthquake
prevention and disaster reduction eorts in the Hetao Basin should
be focused on those faults.
(3) According to historical records, a great earthquake M=
8.0 occurred on October 20, 849A.D., in the Hetao Basin
area causing serious destruction of civilian houses and
thousands of deaths. rough reevaluating the earthquake
intensity and locations of the main damaged place, Yuanetal.
(2023) modied the isoseismal line, which shows that the
earthquake has aected Hetao Basin and its south area with
slow attenuation of seismic intensity on the south side; and
attenuation of seismic intensity is fast with quite small aected
area on the north side, and the WNF is located in the
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FIGURE 10
Cartoon illustration of the evolution model of the Wulashan Northern Fault. (A) Cartoon illustration of geological structure of the Wulashan Northern
Fault in the Neogene. (B) Cartoon illustration of geological structure of the Wulashan Northern Fault in the Holocene.
VIII ∼IX of Intensity Zone (Figure11). e earthquake has
caused obvious surface rupture of the Daqingshan Piedmont
Fault. However, we did not nd any surface rupture on the
WNF in the eld. In addition, the latest activity of the WNF
was Late Pleistocene. So, the WNF did not participate in this
earthquake M= 8.0 in 849A.D.
(4) Although the latest activity era of the WNF given in this
article is weaker than that of adjacent faults and did not
participate in the earthquake M= 8.0, considering the
interaction between faults, that is, the rupture mechanism
triggered by positive Coulomb stress (Shenetal., 2004), the
WNF is located in the positive region of Coulomb Failure Stress
Change (ΔCCFS) by Yinchuan-Pingluo historical earthquake
of M= 8.0 in 1739A.D. During the past nearly 300years,
several earthquakes with a magnitude of about M=∼5
have occurred along the Langshan Piedmont Fault and
Sertengshan Piedmont Fault (Figure2). Considering the
continuous loading of coseismic and post-seismic tectonic
stress, this secondary fault of WNF with a total length of
75km has a relatively higher earthquake risk in the future
which cannot be ruled out. erefore, we should carry
out more work along WNF and consider the possibility of
independent rupture.
6 Conclusion
In this study, we obtained the shallow structural morphology
and checked the Late Quaternary of Wulashan Northern Fault by
two shallow seismic exploration proles and two composite drilling
geological cross-sections in the Hetao Basin, northern side of the
Ordos Block. e following results were obtained:
(1) e Wulashan Northern Fault is a stepped northward-dipping
normal fault system. Among them, the piedmont fault F0 is
a Pre-Quaternary fault. Faults F1 and F2 far away from the
Frontiers in Earth Science 14 frontiersin.org

Wei etal. 10.3389/feart.2024.1437012
FIGURE 11
Isoseismal map of the earthquake in 849A.D. Isoseismic lines from
(Yuanetal., 2023); Location of epicenter from (Heetal., 2020).
Wulashan are Late Pleistocene faults. e latest activity of
the fault Fp1a on the F1 occurred before 40.8 ± 2.5ka. e
maximum vertical dislocation was 0.9m. e latest activities
of the faults Fp2a and Fp2b on the F2 occurred before
73.8 ± 2.8 ka B.P. and 91.2 ± 4.4ka B.P., respectively, and
the maximum vertical dislocation was 0.96m and 1.15m,
correspondingly. Considering the dierent scenarios, the
maximum magnitude of a potential future earthquake was
determined to be M= 6.5–7.0. e Wulashan Northern
Fault was not involved in the 849A.D. M= 8.0 historical
strong earthquake.
(2) As the Wulashan Northern Fault is located in the positive
cumulative region of Coulomb Failure Stress Change
(ΔCCFS) triggered by the Yinchuan-Pingluo M= 8
earthquake in 1739A.D., based on statistics, there is
a very high correlation between positive ΔCCFS and
potential subsequent earthquakes. Although the latest activity
era of the WNF belongs to the late Pleistocene, which
migrated towards the basin, although it is weaker than the
adjacent Holocene active faults (Langshan Piedmont Fault
and Sertengshan Piedmont Fault, Daqingshan Piedmont
Fault and Wulashan Piedmont Fault), further subsequent
research should pay attention to its role of faulting as
independent activities.
Data availability statement
e original contributions presented in the study are included in
the article/supplementary material, further inquiries can be directed
to the corresponding author.
Author contributions
LW: Conceptualization, Data curation, Formal Analysis,
Funding acquisition, Investigation, Methodology, Soware,
Writing–original dra, Writing–review and editing. WH:
Conceptualization, Investigation, Methodology, Project
administration, Resources, Supervision, Writing–review and
editing, Data curation, Formal Analysis, Funding acquisition,
Soware, Validation, Visualization. YX: Supervision, Validation,
Visualization, Writing–review and editing. YD: Data curation,
Investigation, Writing–review and editing. AD: Investigation,
Writing–review and editing. XS: Investigation, Writing–review and
editing. SX: Investigation, Writing–review and editing. JQ: Data
curation, Writing–review and editing.
Funding
e author(s) declare that nancial support was received for the
research, authorship, and/or publication of this article. is research
is jointly nancially supported by the Spark Program of Earthquake
Sciences (No. XH24054YB), Shanxi Taiyuan Continental Ri
Dynamics National Observation and Research Station (Nos.
NORSTY2023-03, NORSTY2021-07), and National Natural Science
Foundation of China (Nos. 42041006, 42072248).
Acknowledgments
We are particularly grateful to Prof. Baojin Liu from the
Geophysical Exploration Center, CEA, Prof. Yongkang Ran, Honglin
He from the Institute of Geology, CEA, and Prof. Qinjian Tian from
the China Earthquake Disaster Prevention Center for their helpful
guidance during the eld survey. We are also extremely grateful
to the Shandong Institute of Earthquake Engineering for the OSL
dating job.
Conict of interest
e authors declare that the research was conducted in the
absence of any commercial or nancial relationships that could be
construed as a potential conict of interest.
Publisher’s note
All claims expressed in this article are solely those
of the authors and do not necessarily represent those of
their aliated organizations, or those of the publisher,
the editors and the reviewers. Any product that may
be evaluated in this article, or claim that may be made
by its manufacturer, is not guaranteed or endorsed by
the publisher.
Frontiers in Earth Science 15 frontiersin.org

Wei etal. 10.3389/feart.2024.1437012
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