Effects of lunar-solar tides in the variations of geophysical fields at the boundary between the Earth’s crust and the atmosphere

Extraterrestrial forcing of natural environmental processes by gravitational interaction between the Sun, the Moon, and the Earth is considered. Based on the instrumental data, the main periodical components and cycles are identified in the time variations of some geophysical fields at the boundary between the Earth’s crust and the atmosphere. Correlation analysis shows that the lunar-solar tides are the key factor responsible for diurnal and quasi-biweekly variations in the ground electric field, radon emanation, water level in wells, and microseismic vibrations. The tidal influence on the various-scale movements of the blocks of the Earth’s crust is analyzed. In the context of the vertical, lateral, and rotational motion of crustal blocks, which is very important for the platforms, a new, precession-like type of displacements is revealed. These movements develop as a result of the nonsynchronous tidal responses of the block and the adjacent interblock gaps or tectonic structures whose strength and strain properties are different in different directions.     

Technique development of PC104 embedded module and its application in the geophysical instrument design

Introduction Electronic technique has been developing to so large scale integrated and high intelligent that the microprocessor has been the core in the electronic equipment or in the process control system design relying on its strong controlling and computing power, convenience to be application designed and to be programmed. Now the mainstream solutions widely used in the geophysical appliance are the single chip microprocessor (MCS), the digital signal processor (DSP), the common compute…     

Study on the Horizontal Deformation Strain Field in the Central and Northern Parts of Yunnan Province

Based on the horizontal deformation field and the strain field derived from the GPS data over the period of 1999～2001 in the Yunnan area, the characteristics of deformation and strain in the northern part of Yunnan Province have been studied. The results indicate that the central part of the studied area is rather stable with little crustal displacement, while the western and eastern parts are active with larger displacement. The strain field reveals that the orientations of the principal compressive strain axis of the crust and the sub-blocks in the area are NW-SE, while the orientations of the principal tensile strain axis is NE-SW. In the studied area, the tensile strain is predominatly in the northern part and the compressive strain is predominatly in the central and southern parts. The stretching direction of the shear-strain contour is basically consistent with the strike of the active fault. The strain and stress fields of the fault activity are related to the structure where the fault is located, while the activity properties of the faults are different.     

Underplating in the middle-lower Yangtze Valley and model of geodynamic evolution:Constraints from geophysical data

~~Underplating in the middle-lower Yangtze Valley and model of geodynamic evolution:Constraints from geophysical data1)East China petroleum Administration,1988(unpublished data). 1)Measurements of regional rock densities and magnetic parameters of Anhui Province(research report),Annul Geological and Mineral Bureau,1987(unpublished). 1)In this paper South China Block(SCB)includes the Yangtze block and Cathaysian block.In the Neoproterozoic the Yangtze block had been sutured to th…     

Space–Time Analysis of Hydrochemical Composition and Pollution of Water in the Northern Dvina Basin

Water Resources - Water quality dynamics along the Northern Dvina River is analyzed under the conditions of anthropogenic impact. Overall, river water is classified as very polluted. The cases of...     

Groundwater–surface water interactions in a river estuary and the importance of geomorphology: Insights from hydraulic,thermal and geophysical observations

This study presents the groundwater flow and salinity dynamics along a river estuary, the Werribee River in Victoria, Australia, at local and regional scales. Along a single reach, salinity across a transverse section of the channel (~80 m long) with a point bar was monitored using time-lapse electrical resistivity (ER) through a tidal cycle. Groundwater fluxes were concurrently estimated by monitoring groundwater levels and temperature profiles. Regional porewater salinity distribution was mapped using 6-km long longitudinal ER surveys during summer and winter. The time-lapse ER across the channel revealed a static electrically resistive zone on the side of the channel with a pronounced cut bank. Upward groundwater flux and steep vertical temperature gradients with colder temperatures deeper within the sediment suggested a stable zone of fresh groundwater discharge along this cut bank area. Generally, less resistive zones were observed at the shallow portion of the inner meander bank and at the channel center. Subsurface temperatures close to surface water values, vertical head gradients indicating both upward and downward groundwater flux, and higher porewater salinity closer to that of estuary water suggest strong hyporheic circulation in these zones. The longitudinal surveys revealed higher ER values along deep and sinuous segments and low ER values in shallow and straighter reaches in both summer and winter; these patterns are consistent with the local channel-scale observations. This study highlights the interacting effects of channel morphology, broad groundwater–surface water interaction, and hyporheic exchange on porewater salinity dynamics underneath and adjacent to a river estuary.     

Evaluation of the Capacity of Comprehensive Earthquake Prevention System in a Region and Its Countermeasures

A model for evaluating the capacity of the comprehensive prevention system in a region in terms of economic losses is established in this paper by using fuzzy mathematics.The authors have explored the weak links of the system mentioned above and suggested an effective procedure of increasing the capacity of earthquake resistance and disaster prevention in a region.Through taking suitable means of decision making,the mathematical model presented in this paper can be used for reference during establishing the comprehensive prevention system in a region to reduce the earthquake disasters.     

The Earth’s crust of the deep platform basins in the Northern Eurasia and their origin

Several large basins with a depth up to 15–20 km are revealed in the platform regions of Northern Eurasia—the Pre-Caspian, Vilyui, Pur-Gydan, and Kara–Barents platforms. All these basins have two structural features in common: they all have a rounded shape with steep walls and are marked with the reduced thickness of the Earth’s crust. With the basins' depth of 15–20 km, the basement top is flat and has an almost horizontal surface. The basins differ by the average seismic velocities in the crystalline crust which vary from 6.2–64 to 6.8–7.0 km/s. Another distinction is the type of the crystalline crust ranging from continental with a thick granite-gneiss layer to suboceanic, represented by the basite layer. For explaining the formation of these basins, we suggest a combined petrophysical model which includes several geodynamical processes of different intensity: rifting, basification, and eclogitization of the Earth’s crust.The model also takes into account the process of material outflow from beneath a basin through the midcrustal layer of increased porosity and fluid saturation. This accounts for the strong reduction of the granite-gneiss layer with the preservation of the basement’s flat surface and for the formation of significant source areas of clastic material around the basin. The formation of these basins requires an extensive and sufficiently laterally uniform and longoperating energy source. The intrusion of the mantle material saturated with fluids into the bottom portions of the crust or, simply, the long-lasting inflow of the deep fluids are the most probable sources of this kind.     

Relocation of the Ms≥2.0 Earthquakes in the Northern Tianshan Region, Xinjiang, Using the Double-Difference Earthquake Relocation Algorithm

We applied the double-difference earthquake relocation algorithm to 1348 earthquakes with M_S≥2.0 that occurred in the northern Tianshan region, Xinjiang, from April 1988 to June 2003, using a total of 28701 P- and S-wave arrival times recorded by 32 seismic stations in Xinjiang. Aiming to obtain most of these M_S≥2.0 earthquakes relocations, and considering the requirements of the DD method and the condition of data, we added the travel time data of another 437 earthquakes with 1.5≤M_S<2.0. Finally, we obtained the relocation results for 1253 earthquakes with M_S≥2.0, which account for 93% of all the 1348 earthquakes with M_S≥2.0 and includes all the M_S≥3.0 earthquakes. The reason for not relocating the 95 earthquakes with 2.0≤M_S<3.0 is analyzed in the paper. After relocation, the RMS residual decreased from 0.83s to 0.14s, the average error is 0.993 km in E-W direction, 1.10 km in N-S direction, and 1.33 km in vertical direction. The hypocenter depths are more convergent than before and distributed from 5 km to 35 km, with 94% being from 5km to 35 km, 68.2% from 10 km to 25 km. The average hypocenter depth is 19 km.     

Relocation of the Ms≥2.0 Earthquakes in the Northern Tianshan Region, Xinjiang, Using the Double-Difference Earthquake Relocation Algorithm

We applied the double-difference earthquake relocation algorithm to 1348 earthquakes with M_S≥2.0 that occurred in the northern Tianshan region, Xinjiang, from April 1988 to June 2003, using a total of 28701 P- and S-wave arrival times recorded by 32 seismic stations in Xinjiang. Aiming to obtain most of these M_S≥2.0 earthquakes relocations, and considering the requirements of the DD method and the condition of data, we added the travel time data of another 437 earthquakes with 1.5≤M_S<2.0. Finally, we obtained the relocation results for 1253 earthquakes with M_S≥2.0, which account for 93% of all the 1348 earthquakes with M_S≥2.0 and includes all the M_S≥3.0 earthquakes. The reason for not relocating the 95 earthquakes with 2.0≤M_S<3.0 is analyzed in the paper. After relocation, the RMS residual decreased from 0.83s to 0.14s, the average error is 0.993 km in E-W direction, 1.10 km in N-S direction, and 1.33 km in vertical direction. The hypocenter depths are more convergent than before and distributed from 5 km to 35 km, with 94% being from 5km to 35 km, 68.2% from 10 km to 25 km. The average hypocenter depth is 19 km.     

Paleoseismicity and Segmentation Along the Active Fault at the Northern Boundary of Huailai-Zhuolu Basin,Hebei Province

The northern boundary fault of Huailai-Zhuolu basin,Hebei Province,has a total length of 58 km and a general strike of NE.The geometry and feature of activity of the 5 segments of the fault greatly differ from each other.17 paleoseismic events have been recognized within 11 trenches excavated along the different segments of the fault.It is found that each segment is characterized by its distinct recurrence of paleoearthquakes.The recurrence intervals of strong earthquakes for each segment are 3500-7000 a for the shortest and 17,000-20,500 a for the longest.However,the recurrence interval of strong earthquakes for whole fault ranges between 750-8500 a.The boundary of the segments can be recognized as the junction,gap,bending,jog and salient of the fault.The length of the segment ranges between 7.5-14 km.     

Characteristics of a Short-Term and Imminent Earthquake Precursor Field in the Northern Part of North China and Numerical Simulation of Source Process

According to studies of more than 20 earthquakes with MS≥5.0 in North China, seven features of the short-term and imminent earthquake precursors have been summarized in this paper. At the same time, taking the short-term and imminent earthquake stage as the physical process of a source's medium softening and fault creep, we calculated temporal variation of mean stress, maximum shear stress, body strain, and pore pressure in some certain points (supposed stations) in the source area and its adjacent area by using an anisotropic and nonlinear source model and a finite element method. According to an analysis of these theoretical curves, we conclude that the short-term and imminent earthquake precursors have such characteristics as complex shapes, exponential growth of the precursor number with tune, and precursors' migration from the outside area to the source area, which to a certain extent reveal the cause of the characteristics of the short-term and imminent earthquake precursor field.     

Holocene Paleoseismic Activity Along the Northern Piedmont Fault of the Hengshan Mountain, South of Datong Basin in Shanxi Province

INTRODUCTIONTheDatongbasinislocatedinthenorthernpartofShanxiProvinceandisoneoftheimportantpartsoftheCenozoicfaultedbasinintheShanxifaulteddepressionsystem .IntheresearchofactivefaultsinChina ,theShanxifaulteddepressionsystemhasattractedgreatattentionwithitsspecifictectonicpatternandfrequencyofhistoricstrongearthquakes (DengQidongetal.,1 973;1 995;LiuGuangxunetal.,1 982 ;DingGuoyuetal.,1 983;XuXiwei,1 989) .AnearthquakewithM6 1occurredintheDatongbasinin 1 989.Sincethenseveraldiscus…     

Systematics of Early Cambrian Paleomagnetic Directions from the Northern and Eastern Regions of the Siberian Platform and the Problem of an Anomalous Geomagnetic Field in the Time Vicinity of the Proterozoic–Phanerozoic Boundary

Representative paleomagnetic collections of Lower Cambrian rocks from the northern and eastern regions of the Siberian platform are studied. New evidence demonstrating the anomalous character of the paleomagnetic record in these rocks is obtained. These data confidently support the hypothesis (Pavlov et al., 2004) that in the substantial part of the Lower Cambrian section of the Siberian platform there are two stable high-temperature magnetization components having significantly different directions, each of which is eligible for being a primary component that was formed, at the latest, in the Early Cambrian. The analysis of the world’s paleomagnetic data for this interval of the geological history shows that the peculiarities observed in Siberia in the paleomagnetic record for the Precambrian–Phanerozoic boundary are global, inconsistent with the traditional notion of a paleomagnetic record as reflecting the predominant axial dipole component of the geomagnetic field, and necessitates the assumption that the geomagnetic field at the Proterozoic–Phanerozoic boundary (Ediacaran–Lower Cambrian) substantially differed from the field of most of the other geological epochs. In order to explain the observed paleomagnetic record, we propose a hypothesis suggesting that the geomagnetic field at the Precambrian–Cambrian boundary had an anomalous character. This field was characterized by the presence of two alternating quasi-stable generation regimes. According to our hypothesis, the magnetic field at the Precambrian–Cambrian boundary can be described by the alternation of long periods dominated by an axial, mainly monopolar dipole field and relatively short epochs, lasting a few hundred kA, with the prevalence of the near-equatorial or midlatitude dipole. The proposed hypothesis agrees with the data obtained from studies of the transitional fields of Paleozoic reversals (Khramov and Iosifidi, 2012) and with the results of geodynamo numerical simulations (Aubert and Wicht, 2004; Glatzmayer and Olson, 2005; Gissinger et al., 2012).     

The Kverkfj?ll fissure swarm and the eastern boundary of the Northern Volcanic Rift Zone, Iceland

Rift zones at the divergent plate boundary in Iceland consist of central volcanoes with swarms of fractures and fissures extending away from them. Fissure swarms can display different characteristics, in accordance with their locations within the ∼50-km-wide rift zones. To better discern the characteristics of fissure swarms, we mapped tectonic fractures and volcanic fissures within the Kverkfj?ll volcanic system, which is located in the easternmost part of the Northern Volcanic Rift Zone (NVZ). To do this, we used aerial photographs and satellite images. We find that rifting structures such as tectonic fractures, Holocene volcanic fissures, and hyaloclastite ridges are unevenly distributed in the easternmost part of the NVZ. The Kverkfj?ll fissure swarm extends 60 km north of the Kverkfj?ll central volcano. Holocene volcanic fissures are only found within 20 km from the volcano. The Fjallgarear area, extending north of the Kverkfj?ll fissure swarm, is characterized by narrow hyaloclastite ridges indicating subglacial volcanism. We suggest that the lack of fractures and Holocene volcanic fissures there indicates decreasing activity towards the north in the easternmost part of the NVZ, due to increasing distance from the long-term spreading axis. We argue that arcuate hyaloclastite ridges at the eastern boundary of the Northern Volcanic Rift Zone are mainly formed during deglaciations, when three conditions may occur; firstly, eruption rate increases due to decompression of the mantle. Secondly, the high tensile stresses accumulated during glaciations due to lack of magma supply may be relieved as magma supply increases during deglaciations. Thirdly, faulting may occur during unloading due to differential movements between the thinner and younger Northern Volcanic Rift Zone crust and the thicker and older crust to the east of it.     

Roman literary and epigraphic sources for the study of historical seismicity in Algeria circa 42–420 ad

The seismicity of Algeria since the nineteenth century is relatively well documented. However, compared with the numerous damaging earthquakes that are documented since 1850, fewer than a dozen reports of earthquakes are listed for the pre-1850 ad period, suggesting that the historical record is missing a substantial number of earthquakes. This paper examines the use of literary and epigraphic sources relevant to the investigation of seismicity in Algeria during Roman times. We provide examples where the meager written literary record may be supplemented with appropriate archaeological and epigraphic data describing damage to ancient Roman sites. The examples show that collaboration between earth scientists and archeologists is of utility in improving the seismic record and highlights the need for further study of data sources and repositories located both inside and outside of Algeria.     

Deformation of the Earth’s crust in the Northern Tien Shan according to the earthquake focal data and satellite geodesy

For evaluating the deformations of the Earth’s crust in the Northern Tien Shan, we calculated the mode and intensity of the seismotectonic deformations (STD) for this region. The input for these calculations were the catalog data on the focal mechanisms of earthquakes, obtained by wave inversion of the signals recorded at the Kyrgyz seismic network (KNET) for the period 1994–2006. In the construction of STD maps, a modern approach to the classification of seismotectonic deformations was applied. This approach distinguishes eleven typical patterns of deformation. The areal distributions of the Lode-Nadai coefficient, as well as of the vertical component and the aspect angle of the deformed state were obtained. At the same time, based on the GPS measurements in the Northern Tien Shan during 1994–2006, the rates of dilatation and shear deformation of the Earth’s crust were estimated. A comparison between the directions of strain axes derived from the GPS data and from the earthquake focal data is carried out.     

Temporal and spatial variation and stability of the oasis in the Sangong River Watershed, Xinjiang, China

The unique ecological landscapes are composed of the mountain systems with the obviousvertical differentiation, vast natural desert systems, and oasis systems on which the human beings rely for the existence in the arid areas in West China. Oases are the …     

Passive Seismic Experiment “13 BB Star” in the Margin of the East European Craton,Northern Poland

The lithosphere-asthenosphere boundary (LAB) is investigated recently very effectively, mostly using seismic methods because of their deep penetration and relatively good resolution. The nature of LAB is still debated, particularly under “cold” Precambrian shields and platforms. Passive experiment “13 BB star” is dedicated to study deep structure of the Earth’s interior in the marginal zone of the East European craton in northern Poland. The seismic network consists of 13 broadband stations on the area of ca. 120 km in diameter. The network is located in the area of well-known sedimentary cover and crustal structure. Good records obtained till now, and expected during next 1-year long recording campaign, should yield images of detailed structure of the LAB, ?410”, “?520”, and ?660” km discontinuities, as well as mantle-core boundary and inner core.