Deep Seismic Sounding Research Articles

Features and mechanism of neotectonic deformation of the Xishan fault system west of Urumqi

We have made careful field investigation and trench exploration to the Xishan fault system in west of Urumqi, and an integrated analysis in conjunction with data of deep seismic sounding. Our result suggests that under the SN-oriented compressive stress, the Xishan block moves steadily toward the Tianshan Mountains in south, resulting in southward thrust-slip and crustal shortening, particularly the southward thrust of the Xishan fault which serves as the main boundary in south. North of the Xishan fault are the Wangjiagou fault and Jiujiawan fault which are the secondary faults associated with the Xishan fault in generation. Both faults have slippage along horizons during the uplift of the Xishan block, and the Jiujiawan fault has also a component of normal faulting due to the influence of the Bogeda nappe structure. These two faults accommodate the fold deformation of the hanging wall of the Xishan fault, thus the Xishan fault-bounded swell is characterized by monocline. All secondary faults of the Xishan fault system constitute a common seismogenic structural system, so that their seismic hazards should be considered in an equal manner.

Lithospheric electrical imaging of the Deccan trap covered region of western India

We present here the results of magnetotelluric (MT) studies carried out along a 330 km long NE‐SW trending traverse from Daulatabad at the northeastern end to Koyna on the southwestern end across the Deccan volcanic province (DVP) in western India. The 2‐D MT modeling results obtained along this traverse together with those from other MT traverses in this area are examined and integrated with the results from deep seismic sounding, 3‐D teleseismic tomography, and heat flow studies. The deep geoelectric section as deduced from MT models point out to a two layered lithospheric mantle structures with an upper very high‐resistive layer (several thousands of ohm m) and a bottom relatively conductive one (a few tens of ohm m to a few hundred ohm m). The lithospheric electrical structure is inferred to be linked to compositional changes associated with a depleted lithospheric upper mantle in the Dharwar craton. An impressive feature that the study has brought out is the presence of a well‐defined lithospheric upper mantle conductor in the depth range of 80–120 km limited to the middle segment of the MT traverse from Sangole to Partur over the DVP. The electrical characterization of the region including the presence of upper mantle conductor shows close similarities with that of other similar cratonic regions like the Slave and Superior cratons in northwestern Canada.

Crustal Structure of the Rift‐Depression Basin and Yanshan Uplift in the Northeast Part of North China

AbstractA comparatively complete layout chart is built by using small shot interval and receiver spacing in Tianjin–Beijing–Chicheng Deep Seismic Sounding profile. Based on the DSS data of the profile, the crustal structure and the tectonic coupling are studied in the rift‐depression basin of eastern North China and Yanshan mountain uplift. Based on the existing researches in the region, the seismic structure environment is further analyzed in the eastern segment of Zhangjiakou–Bohai seismic belt. The result shows that the tectonic feature and interface structure of the crystalline basement in the rift‐depression basin of eastern North China Craton are correlated with the geotectonic movement since Cenozoic era. The entirely different crustal structures between the stable Yanshan uplift with high velocity in the north and the incompact rift basin with low velocity in the south make the intergradational zone between the tectonic zoning line, Baodi–Tongbai and Ninghe–Changli faults, and Yanshan uplift provide a favorable structural environment for generation and occurrence of earthquakes in the eastern plain region of Zhangjiakou–Bohai seismic belt.

Crustal Structure of the Western Bengal Basin from Joint Analysis of Teleseismic Receiver Functions and Rayleigh-Wave Dispersion

Teleseismic data recorded at the broadband seismological observatory of the Indian Institute of Technology (IIT) Kharagpur are analyzed to determine the seismic characteristics of the crust beneath the western Bengal basin. Receiver functions calculated from the teleseismic P waveform for a range of back azimuths show little variation in the Moho Ps arrival time, indicating a nearly one-dimensional crustal structure beneath Kharagpur. Transforming the time domain receiver functions into the H - V p / V s domain for a stack of all receiver functions reveals a 38±2 km thick crust with a V p / V s of 1.73±0.01. Receiver functions stacked in narrow bins of back azimuth and great-circle-arc distance were inverted jointly with group velocity dispersion data for periods from 15 to 45 sec. Joint inversion results reveal a near surface sedimentary layer of ∼1.5 km thickness, a 13 km thick upper crust, and a 23 km thick lower crust with the Moho at a depth of ∼37.5 km. The average crustal S -wave velocity is 3.7 km/sec. The top 0.5 km of the sedimentary layer has very low S -wave velocity and a large impedance contrast with the underlying layer. This represents the thin layer of unconsolidated sediments and weathered laterites near the surface as seen from deep seismic sounding (DSS) studies across the region. The S -wave velocity structure of the crust beneath Kharagpur is the first such result for the western Bengal basin and is broadly similar to that of the Indian Shield crust. A comparison of the crustal thickness and lower crustal velocities between Kharagpur and Agartala, seperated by the Eocene hinge zone, shows remarkable differences. Crustal models beneath Agartala reveal ∼36 km thick crust with the presence of a high-velocity lower crust (∼6 km thick), possibly oceanic in nature, which is absent beneath Kharagpur. The hinge zone, therefore, separates the continental crust of the western Bengal basin from the eastern deep basinal oceanic crust, both being overlain by sediments derived from the Himalayas.

The structure of the tectonosphere of the Urals and West Siberian Platform by electromagnetic data

Advances in magnetotelluric sounding (MTS) have provided the possibility to study deep parts of the planet and obtaining information on electroconductivity of the Earth’s tectonosphere, which is very sensitive to the lithology of rocks in the upper part of the crust, as well as to the phase state of substance, the temperature, concentration, and mineralization of fluids. Introduction of modern broadband digital measuring and computation equipment, as well as programs of computational modeling allowed us to realize more completely the possibilities of geoelectric methods. The technical approach including the integration of geoelectric methods, the processing of experimental materials, and interpretation of data with construction of geoelectric models of the medium was considered in detail by the example of geotraverses through the Northern and Southern Urals [1, 2]. The material on the study of fields of natural sources of geomagnetic variations of the ionospheric and magnetospheric origin (AMT‐MTS‐DMTS methods) and the induction electromagnetic sounding (IEMS) method with a controlled source along a traverse about 1000 km long from the Settlement of Askino (Bashkortostan) in the west to Tyukalinsk (Omsk oblast) in the east with an a posteriori test of the previously obtained results [3] was generalized for the first time in this work; the geotraverse partially coincides with the Sverdlovsk profile of deep seismic sounding (DSS). In this case, major faults and zones of higher fracturing in the crust, as well as relationships between electroconductivity and the tectonic structure of regions, were studied. The originality of the studies performed lies in the fact that peculiarities of tectonosphere stratification were traced by electric parameters within a depth from 10 m to 600 km, and traces of events that proceeded there over a large time interval were revealed. The results are presented in Fig. 1. According to the distribution of total longitudinal conductance of the lithosphere ( S ), the territory under consideration can be subdivided into three sectors, the boundaries of which mark zones of abnormally high conductivity, which

Crustal structure in the Barents-Kara region from detailed surveys by the method of deep seismic sounding. Paper 2

Seismogeologic sections for the Barents-Kara region along geotraverses 1-AR, 2-AR, and 3-AR with a total length of about 4000 km were obtained using the GODOGRAF software package developed at the Department of Seismometry and Geoacoustics of the Moscow State University. The data were travel times of refracted waves excited by approximately 100 sources along each traverse. This paper reports sections for the 3-AR traverse covering areas of the White Sea, Pechora Sea, and Kara Sea, and a geological interpretation of these. The sections cover depths down to 40–50 km and show basic crustal discontinuities, fold-thrust, rift, and paleospreading structural features, and paleosubduction zones. We characterize the possible character of the junction between the South Kara and North Kara basins. A geodynamic interpretation of the structures is provided for the Barents-Kara region.

Crustal structure beneath the Iberian Peninsula and surrounding waters: A new compilation of deep seismic sounding results

We present here an updated compilation of crustal parameters beneath the Iberian Peninsula and surrounding waters, inferred from extensive deep seismic exploration performed in the last three decades. Firstly, the more relevant experiments developed in both terrestrial and marine domains are revisited, together with the corresponding seismic velocity–depth models published that reveal the characteristics of the different tectonic domains sampled, including oceanic zones, continental margins, orogenic and rift belts. The results are summarized in three crustal transects sketched along representative directions. Secondly, we compiled the Moho depths along all the available seismic profiles to produce a geo-referred database. This database has then been interpolated using kriging algorithms to obtain a continuous Moho depth model, in the form of a regular grid file. This integrative Moho map for a key area in the Western Mediterranean documenting the interaction between European and African plates can contribute to constrain further regional studies, either at crustal, lithospheric or mantle scales.

Moho deepening and shallow upper crustal delamination beneath the central Apennines

Geologic interpretation of seismic data along the eastern half of the CROP 11 deep seismic reflection profile, running across the central Apennines, indicates that the Adriatic Moho deepens gradually from 34 km in the foreland areas to 47 km beneath the core of the belt. This deepening is in agreement with local Moho depths estimated from teleseismic receiver functions at several stations installed along the CROP 11 profile. On the contrary, DSS (Deep Seismic Soundings) data image the Moho at shallower depths. The deepening of the Adriatic Moho illustrated in this paper supports the westward downgoing of a portion of Adriatic continental crust and is consistent with the regional gravity anomalies, provided that very high-density rocks are present above the Moho at the core of the central Apennine belt. We discuss geophysical and geologic data in the framework of alternative models of delamination of the Adriatic crust at different depth.

Comprehensive Geophysical Research on the Deep Structure of Northeastern South China Sea

AbstractThe complex crustal structure of northeastern South China Sea and neighboring areas, especially the structure of the land‐sea transition zone, has been a hot subject of the lithospheric structure research of South China Sea. In this paper we construct the density model along two profiles based on gravity data and constraints from Pn wave tomography and deep seismic sounding. The result of 2.5D density modeling supports the point of view that a high velocity layer exists in the lower crust of the area from Qiongyue Uplift to Luzon island arc; and the fitting result to the Taixinan Basin indicates that the crust in the southern depressed region should belong to the transitional type. Although the tectonic feature of the northeastern shelf of South China Sea is generally of volcanic type, the structures of profile AA' and BB' are different, which indicates the lateral variation and the complexity of crustal structure in the northeastern margin of South China Sea.

S-Wave Attenuation Characteristics beneath the Vrancea Region in Romania: New Insights from the Inversion of Ground-Motion Spectra

The S -wave attenuation characteristics beneath the Vrancea region in Romania are analyzed from the spectra (frequency range 0.5–20 Hz) of more than 850 recordings at 43 accelerometric stations of 55 intermediate-depth earthquakes ( M 4.0–7.1) that occurred in the Vrancea seismogenic zone. The method commonly chosen for this type of investigation in the case of crustal earthquakes is the generalized inversion technique (GIT) (e.g., Andrews, 1986; Castro et al. , 1990). Yet the Vrancea dataset is entirely different from common crustal datasets. Because of the strong clustering of the hypocenters within a very small focal volume, there are only few crossing ray paths from sources to receivers. As a consequence, inhomogeneities in the attenuation properties are not averaged out, which leads to unphysical results if the standard GIT approach is adopted. The problem is discussed qualitatively by performing tests with synthetic data and solved quantitatively by adapting the GIT technique in view of these peculiarities. With the optimally adapted inversion scheme, it is possible to unravel differences in the attenuation characteristics between two (or more) sets of stations. The results show that the attenuation of seismic waves is roughly comparable in the low frequency range (<4–5 Hz) but stronger by up to an order of magnitude at higher frequencies within the Carpathian mountain arc as compared with the foreland area. Modeling this strongly frequency-dependent lateral variation of seismic attenuation by a significantly lower Q beneath Vrancea (1) provides a very good fit of observed strong-motion characteristics, (2) sheds new light on the distribution of intensities of the previous strong earthquakes, (3) will have strong implications for future hazard assessment, and (4) is fully compatible with structural models from deep seismic sounding, tomography, and teleseismic attenuation.

A Study on the Crust Phases of Deep Seismic Sounding and the Fine Crust Structure in the Northeast Margin of Tibetan Plateau

AbstractIn this paper the fine crust structures of the different tectonic units in the northeastern margin of Tibetan plateau are investigated in detail by means of comprehensive analyses of the crust phases on the recording sections of deep seismic sounding experiments in this region and comparing the observed seismic recording sections with the synthetic seismograms computed by the reflectivity method. The results reveal that the crust structures in the northern and southern parts of this region separated by the western Qinling fold zone are quite different, and the crust structures are characterized respectively by stable Linxia‐Lanzhou Cenozoic basin in the northern part and by strongly rebuilt Songpan‐Garzê tectonic block in the southern part. The results also show that Songpan‐Garzê tectonic block was rebuilt as two types of crust structures, i.e. the type of the shrunken Zoigê upland basin and the type of the folded orogenic zone in the basin margin. It is also revealed that the fractured and relaxed structure widely exists in the mid and low crust in the northeastern margin of Tibetan plateau, which is characterized by alternative low and high velocity structures or low velocity distributions. This structural feature appears especially obvious in the suture zone and the orogenic zone, which implies there are important places of thickening of the crust and rheological slip motion. The crust deformation and geodynamic process are discussed based on the 2D‐velocity structure of the crust and GPS result obtained in this region.

Tectonics and thermal structure of western Satpura, India

Increased seismicity and occurrences of hot springs having surface temperature of 36–58 °C are observed in the central part of India (74–81° E, 20–25° N), where the NE trending Middle Proterozoic Aravalli Mobile Belt meets the ENE trending Satpura Mobile Belt. Earlier Deep Seismic Sounding (DSS) studies along Thuadara-Sendhwa-Sindad profile in the area has showed Mesozoic Sediments up to around 4 km depth covered by Deccan Trap and the Moho depth with a boundary velocity ( P n ) of 8.2 km/s. In the present study, surface heat flow of 48 ± 4 mW m −2 has been estimated based on P n velocity, which agrees with the value of heat flow of 52 ± 4 mW m −2 based on Curie point isotherms estimates. The calculated temperature-depth profile shows temperature of 80–120 °C at the basement, which is equivalent to oil window temperature in Mesozoic sediments and around 570–635 °C at Moho depth of 38–43 km and the thermal lithosphere is about 110 km thick, which is comparatively higher than those of adjoining regions. The present study reveals the brittle–ductile transition zone at 14–41 km depth (temperature around 250–600 °C) where earthquake nucleation takes place.

Crustal stucture of the Barents-Kara Region based on detailed deep seismic sounding

In 1995–1998 and 2003–2005, detailed deep seismic soundings were undertaken in the Barents-Kara Region along geotraverses 1-AR, 2-AR, 3-AR with a total length of over 3000 km. Seismic cross-sections, up to 50 km deep as an average, were obtained using the software package GODOGRAPH designed at the Department of Seismometry and Geoacoustics of the Lomonosov Moscow State University. The study was based on refraction traveltime curves with approximately 100 curves per profile. The sections obtained along the 1-AR and 2-AR traverses were geologically interpreted. The main crustal boundaries, fold-thrust structural features of the lower crust and a suture zone between the North Barents Basin and the Caledonian Orogenic Belt were distinguished. Based on our data, the structure of the suture can be interpreted as an ancient subduction zone. The possible pattern of tectonic movements of the Barents Plate is characterized.

Structural architecture of the central Apennines: Interpretation of the CROP 11 seismic profile from the Adriatic coast to the orographic divide

We present an interpretation of the eastern half portion of the CROP 11 line, a deep reflection seismic profile 265 km long that cuts across the central Apennines from the Tyrrhenian coast to the Adriatic coast. In the study area the line cuts across a pile of thrust sheets that underwent tectonic transport between the Messinian and the Pleistocene. In its easternmost part, the line runs through the Plio‐Pleistocene deposits of the Adriatic foredeep. In the foreland region the CROP 11 line integrates previous information on the crustal structure derived from petroleum exploration and from deep seismic sounding refraction experiments. In particular, the CROP 11 line confirms the existence of a very thick sedimentary sequence underlying the Mesozoic‐Tertiary carbonates of the Apulia Platform interpreted as the Paleozoic‐Triassic sedimentary cover of a pre‐Cambrian crystalline basement. In the mountain chain, where the base thrust of the orogenic wedge reaches a depth of about 25 km, this sedimentary sequence appears to be the deepest geological unit incorporated in the thrust system. This interpretation of the CROP 11 profile suggests an unusual thin‐skin tectonic style implying the detachment from the original basement and the incorporation in the post‐Tortonian tectonic wedge of a very thick Paleozoic‐Triassic sedimentary sequence possibly affected by low‐grade metamorphism in the lower part. Other new suggestions from the CROP 11 seismic data concern the origin of the Fucino basin, one of the most remarkable Plio‐Pleistocene intramontane basins. The normal faults bordering this structural depression, as other important normal faults present in the central Apennines (e.g., the Caramanico fault system in the Majella region), seem to have been controlled by gravitational‐collapse processes driven by uplift during crustal shortening rather than by a generalized extension subsequent to the Apennine compression, as usually reported in the geological literature. If this interpretation is correct, the strong seismic activity in correspondence to the Apennine watershed may be related to the very recent increase in the structural relief caused by an out‐of‐sequence propagation of the active thrusts.

Một số kết quả xây dựng mô hình mật độ vỏ Trái đất Miền Bắc Việt Nam bằng bài toán 2,5 chiều trọng lực, kết hợp sử dụng tài liệu địa chấn dò sâu

Crustal density model of north Vietnam by 2,5d gravity analysis in combination with deep seismic sounding

10.1007/s11711-008-1001-1

This paper considers the results from seismic investigations of the Kuril-Kamchatka trench (KKT) using continuous seismic profiling (CSP), the common-depth point (CDP), and deep seismic sounding (DSS). The outcome is an approximate 2D seismic model that reflects the overall structure of the landward trench slope for most of the KKT, with the greatest departure of the data from the model being for the middle Kuril Islands area. A deep-seated fault has been identified in the upper part of the slope 60–80 km from the trench axis, with the fault being traceable throughout the depth interval between the seafloor and the bottom of the crust. In the portion between the fault and the trench axis the seismic velocities are lower, the gradient higher, and the crust thins rapidly seaward. The sediment thickness on the landward slope varies along the trench, reaching the maximum off the southern Kuril Islands. The structural variations along the KKT show a broad correlation with the behavior of geophysical fields and seismicity, which seems to be an expression of global tectonic processes.

Study on Crustal Composition and Geodynamics Using Seismic Velocities in the Northeastern Margin of the Tibetan Plateau

AbstractBased on P‐wave, S‐wave velocity structures and Poisson's ratio of the Maqin‐Lanzhou‐Jingbian seismic refraction/wide angle reflection profile, which crosses the northern Bayan Har block, the Qinling block, the Qilian block, the Haiyuan arcuate tectonic region, and the Ordos block, the crustal composition of the northeastern margin of the Tibetan plateau is studied and the geodynamic issues are discussed. At first, a set of feasible methods are systemically summed up, with which in situ P‐wave velocities observed by deep seismic sounding can be corrected to the velocity under the special condition of temperature and pressure in the laboratory. It is the key to the methods to get temperatures in the crust using heat flow. The second, in situ P‐wave velocities of the profile are corrected to the velocities under a standard pressure of 600 MPa and room temperature, the corrected velocities, combined with Poisson's ratio, are compared with laboratory measurements of ultrasonic velocities, and the crustal petrologic composition is determined in the study area. Results show that the average corrected velocity in the northeastern margin of the Tibetan plateau is 6.43 km/s, and the bulk crustal composition is felsic like the composition of the upper crust. In the Bayan Har block and southern part of the Qinling block, there is a lack of Vp &gt; 6.9 km/s mafic rock layer in the lowest crust, instead there are alternating felsic and intermediate layers in the lower crust, and the bulk composition of the lower crust is felsic. In other blocks, there is a 2~10 km thick mafic layer of Vp &gt; 6.9 km/s and the bulk composition is intermediate in the lower crust. At last, on the basis of the crustal structure and composition in the northeastern margin of the Tibetan plateau, the opinion that crustal thickening occurred mainly in the lower crust is supported, and it is proposed that delamination possibly occurred in the lower crust of the Bayan Har block and southern Qinling block in the recent geologic time, which accelerated the uplift of the Tibetan plateau.

S-wave crustal and upper mantle’s velocity structure in the eastern Tibetan Plateau — Deep environment of lower crustal flow

A teleseismic profile consisting of 26 stations was deployed along 30°N latitude in the eastern Tibetan Plateau. By use of the inversion of P-wave receiver function, the S-wave velocity structures at depth from surface to 80 km beneath the profile have been determined. The inversion results reveal that there is significant lateral variation of the crustal structure between the tectonic blocks on the profile. From Linzhi north of the eastern Himalayan Syntaxis, the crust is gradually thickened in NE direction; the crustal thickness reaches to the maximum value (∼72 km) at the Bangong-Nujiang suture, and then decreased to 65 km in the Qiangtang block, to 57–64 km in the Bayan Har block, and to 40–45 km in the Sichuan Basin. The eastern segment of the teleseismic profile (to the east of Batang) coincides geographically with the Zhubalong-Zizhong deep seismic sounding profile carried out in 2000, and the S-wave velocity structure determined from receiver functions is consistent with the P-wave velocity structure obtained by deep seismic sounding in respect of the depths of Moho and major crustal interfaces. In the Qiangtang and the Bayan Har blocks, the lower velocity layer is widespread in the lower crust (at depth of 30–60 km) along the profile, while there is a normal velocity distribution in lower crust in the Sichuan Basin. On an average, the crustal velocity ratio (Poisson ratio) in tectonic blocks on the profile is 1.73 (σ = 0.247) in the Lhasa block, 1.78 (σ = 0.269) in the Banggong-Nujiang suture, 1.80 (σ = 0.275) in the Qiangtang block, 1.86 (σ = 0.294) in the Bayan Har blocks, and 1.77 (σ = 0.265) in the Yangtze block, respectively. The Qiangtang and the Bayan Har blocks are characterized by lower S-wave velocity anomaly in lower crust, complicated Moho transition, and higher crustal Poisson ratio, indicating that there is a hot and weak medium in lower crust. These are considered as the deep environment of lower crustal flow in the eastern Tibetan Plateau. Flowage of the ductile material in lower crust may be attributable to the variation of the gravitational potential energy in upper crust from higher on the plateau to lower off plateau.

Upper crust structure of eastern A’nyemaqên suture zone: Results of Barkam-Luqu-Gulang deep seismic sounding profile

Barkam-Luqu-Gulang deep seismic sounding profile runs from north of Sichuan Province to south of Gansu Province. It is located at the northeastern edge of Tibetan Plateau and crosses eastern A’nyemaqen suture zone. The upper crust structures around eastern A’nyemaqen suture zone and its adjacent area are reconstructed based on the arrival times of refracted Pg and Sg waves by using finite difference method, ray tracing inversion, time-term method and travel-time curve analysis. The results show that the depth variation of basement along profile is very strong as indicated by Pg and Sg waves. The basement rose in Zoige basin and depressed in eastern A’nyemaqen suture zone, and it gradually rose again northward and then depressed. The results also indicate that eastern A’nyemaqen suture zone behaves as inhomogeneous low velocity structures in the upper crust and is inclined toward the south. Hoh Sai Hu-Maqen fault, Wudu-Diebu fault and Zhouqu-Liangdang fault are characterized by low velocity distributions with various scales. The distinct variation in basement depth occurred near Hoh Sai Hu-Maqen fault and Zhouqu-Liangdang fault, which are main tectonic boundaries of A’nyemaqen suture zone. Wudu-Diebu fault, located at the depth variation zone of the basement, possibly has the same deep tectonic background with Zhouqu-Liangdang fault. The strongly depressed basement characterized by low velocity distribution and lateral inhomogeneity in A’nyemaqen suture zone implies crushed zone features under pinching action.

Three-Dimensional P-Wave Velocity Structure of the Crust of North China

Since the Xingtai earthquake in 1966, China Earthquake Administration has carried out a survey campaign along more than thirty deep seismic sounding (DSS) profiles altogether about twenty thousand kilometers long in North China to study the velocity structure of the crust and the upper mantle in this region, and has obtained a great number of research findings. However, these researches have not provided a 3D velocity structure model of the crust of North China and cannot provide seismic evidence for the study of the deep tectonic characteristics of the crust of the whole region. Hence, based on the information from the published data of the DSS profiles, we have chosen 14 profiles to obtain a 3D velocity structure model of North China using the vectorization function of the GIS software (Arc/Info) and the Kriging data gridding method. With this velocity structure model, we have drawn the following conclusions: (1) The P-wave velocity of the uppermost crust of North China changes dramatically, exhibiting a complicated velocity structure in plane view. It can be divided into three velocity zones mainly trending towards north-west. In the research area, the lowest-velocity zones lie in the Haihe plain and Bohai Bay. Although the geological structure of the sedimentary overburden in the study area is somewhat inherited by the upper crust, there are still several differences between them. (2) Generally, the P-wave velocity of the crust increases with depth in the study area, but there still exists local velocity reversion. In the east, low-velocity anomalies of the Haihe plain gradually disappear with increasing depth, and the Shanxi graben in the west is mainly characterized by relatively low velocity anomalies. Bounded by the Taihang Mountains, the eastern and western parts differ in structural trend of stratum above the crystalline basement. The structural trend of the Huanghuaihai block in the east is mainly north-east, while that of the Shanxi block and the eastern edge of the Ordos block is mainly north-west. (3) According to the morphological features of Moho, the crust of the study area can be divided into six blocks. In the Shanxi block, Moho apppears like a nearly south-north trending depression belt with a large crustal thickness. In the southern edge of the Inner Mongolia block and the south of the Yanshan block, the Moho exhibits a feature of fold belt, trending nearly towards east-west. In the eastern edge of the Ordos block, the structure of Moho is relatively complex, presenting a pattern of fold trending nearly towards north-west with alternating convexes and concaves. Beneath the Huanghuaihai block, the middle and northern parts of the North China rift zone, the Moho is the shallowest in the entire region, with alternating uplifts and depressions in its shape. For the anteclise zone in the west of Shandong Province, the Moho is discontinuous for the fault depression extending in the north-west direction along Zaozhuang -Qufu