EW Direction Research Articles

Investigating tropospheric effects and seasonal position variations in GPS and DORIS time-series from the Nepal Himalaya

SUMMARY Geodetic time-series from continuous GPS (cGPS) and 1 DORIS stations across the Himalaya of central Nepal show strong seasonal fluctuations observed on the horizontal and vertical components. Because the fluctuations determined at the different stations have similar phase but different amplitudes, these observations would imply that the secular shortening across the range is modulated by a seasonal strain. Given the geographic and climatic setting, there is however a possibility that the GPS positions be biased by tropospheric effects. We process these data using two different software packages and two different analysis strategies. Our analysis shows evidence for 1-strong seasonal fluctuation of zenithal delays consistent with in situ meteorological data and two strong horizontal tropospheric gradients in particular in the EW direction, that is, parallel to the mountain front at Gumba, also detected in DORIS results. We show that the tropospheric effects cannot however be the source of the observed seasonality of horizontal strain. This study supports the view that the seasonal strain in the Himalaya is real and probably driven by seasonal surface load variations. Our study adds support to the view that seasonal variations of seismicity in the Himalaya reflects seasonal variations of geodetic strain.

Development characteristics and quantitative prediction of reservoir fractures in the Chaoyanggou oil field

The Chaoyanggou oil field is a fractured low-permeability reservoir, where the distribution of oil and gas is controlled by the distribution and development of fractures. Based on outcrop, drilling core, thin section and log data, the development characteristics of fractures in this area are described. On this basis, the degree of fracture development was predicted by quantitative analysis of fracture strength and numerical simulation. The result shows that four groups of structural fractures, i.e., in near NS, and EW directions and in due NW and NE directions, were developed in the reservoir, with the nearly NS and EW fractures dominant, which are the along bedding decollement fractures formed by compressive folding action, while low angle shear fractures are related to thrusts. These fractures are mainly formed in the reversed tectonic stage at the end of the Mingshui formation during the Cretaceous period. The degree of fracture development is controlled by such factors as lithology, stratum thickness, faults, folds and depth. The fractures are developed with a clear zonation and are best developed in the northern zone, moderately developed towards the south and poorly developed in the middle zone. These prediction results are in good agreement with interpretation results from logs.

Analysis and Interpretation of Aeromagnetic Data for East of Nasser Lake Area, Aswan, Egypt

The area of study is located to the south east of Aswan occupying part of Nasser Lake in its western section. Nasser Lake is contemplated as a source of tectonic instability and earthquake activities in Aswan region. Most of this activity was recorded in the western side of the lake, coincides with the intersections of the two major fault systems, trending in the NS and EW directions. Therefore, mapping the subsurface structures in the study area can shed more light on the structural setting of this zone of the lake and its relation to tectonic instability. This study presents the analysis and interpretation of aeromagnetic data to map the subsurface structural framework of the area around the Lake. Structural interpretation of the magnetic data was achieved through applying advanced interpretation techniques that provide automatic delineation and depth estimation of the magnetic structures. These techniques include Horizontal Gradient, Euler deconvolution and Local wave number. The structure locations and depths obtained from these methods were integrated to delineate the tectonic framework of the area. The mapped structures reveal that the area is affected by a set of faults trending mainly in the NW-SE, EW, NS and NE-SW directions. Moreover, the area is dissected by basement uplifts and troughs controlled mainly by the NW-SE faults.

Local stress concentration in the seismic belt along the Japan Sea coast inferred from precise focal mechanisms: Implications for the stress accumulation process on intraplate earthquake faults

Spatial changes in the azimuth of the maximum principal stress (σ1) axis are found in the intraplate region of southwest Japan. It is inferred from stress inversions of numerous precise focal mechanisms that the azimuths of the σ1 axis in the seismic belt along the Japan Sea coast are oriented in N110°E–N130°E directions, while in the surrounding region they are aligned in almost the EW direction, N90°E–N100°E. Maximum horizontal compressional stresses in an EW direction are widely observed in the shallow crust in the inland plate along the Nankai Trough. However, the maximum horizontal stress in a WNW–ESE direction is seen only in the seismic belt. This spatial change in the stress field in and around the seismic belt is explained by the deformation of an aseismic fault or a ductile fault zone in the lower crust beneath the seismic belt.

Variations of shear wave splitting in the 2008 Wenchuan earthquake region

Through the analysis of S-wave particle motion of local events in the shear wave window, the polarization directions of the faster shear wave and the delay times between the faster and the slower shear waves were derived from seismic recordings at the stations near the fault zones. The shear wave splitting results of seven stations in the area of Longmenshan fault zone reveal spatial variation of the polarization directions of the fast shear wave. The directions at stations in the southeastern side of the Longmenshan fault zone (in the Sichuan Basin area) are in the NE direction, whereas the direction at station PWU (in the Plateau), which is in the northwestern side of the faults, is in the EW direction. Systematic changes of the time delays between two split shear waves were also observed. At station L5501 in the southern end of the aftershock zone, the delay times of the slower shear wave decrease systematically after the main shock. After the main shock, the delay times at station PWU were longer than those before the earthquake. Seismic shear wave splitting is caused mostly by stress-aligned microcracks in the rock below the stations. The results demonstrate changes of local stress field during the main-shock and the aftershocks. The stress in the southern part of Wenchuan seismogenic zone was released by the main-shock and the aftershocks. The crustal stresses were transferred to the northeastern part of the zone, resulting in stress increase at station PWU after the main-shock.

Delineation of potential groundwater zones in the Kagna river basin of Gulburga district, Karnataka, India using remote sensing and GIS techniques

The potential groundwater zones in parts of Kagna river basin of Gulburga district, Karnataka, have been delineated on the basis of geomorphic units alongwith geological setting, lineaments indicating bore well locations using remote sensing and GIS. The study area covers an area of 1318 sq km and it is divided into Wadi, Chitapur, Sedam and Kurkunta sub-basins which range in area from 184 to 537 sq km. Lithologically, the area consists of basement gneisses with granites overlain by conglomerate, sandstone, shale and limestone with a thin cover of Deccan basalts. Hydrogeomorphologically, the entire area is classified into escarpment slope, pediments, pediment inselberg complex, shallow pediplains, moderate pediplains, slightly to highly dissected and undissected plateaus, valleys and shallow valley fills. The lineaments representing drainages and dykes are oriented in NNW, NW, EW and NE directions. Most of boreholes are located nearer to the lineaments indicating that the lineaments are acting as pathways for the movement of groundwater. Based on lineament and hydrogeomorphic analysis, it is suggested that the valley fills and moderate pediplains are very good to good, shallow pediplains and dissected plateau are good to moderate, pediments are moderate to poor and the pediment inselburg complex and escarpment slope are the poor to very poor potential groundwater zones.

Crustal Structure and Its Tectonic Responses During Mesozoic and Cenozoic in Beijing‐Tianjin‐Tangshan and Its Adjacent Region

AbstractTaking the North China block as the demonstration zone of “Images of the Earth's Crust & Upper Mantle (IGCP Project 474)”, we calculated the average velocity and thickness of the upper, middle, and lower crust in Beijing‐Tianjin‐Tangshan (BTT) and adjacent areas by integrating crustal velocity structure from eight wideangle reflection seismic profiles in this region. Using Kriging interpolating technique, the authors have constructed many significant images such as average velocity, thickness and spatial variation of the bottom boundary depths of upper crust, mid‐crust and lower crust. These images show that uplift and depression spreading along nearly EW and NE directions dominate in the study region. Faulted‐swells and faulted‐ depressions controlled by NE faults are present too. The formation of geological structure is closely related to tectonic movement that occurred since the Mesozoic in the study region. The authors inferred that there were at least three stages of intense tectonic movements in the Mesozoic and Cenozoic in the study region. Combining with regional tectonic researches, the authors conclude that the nearly EW uplifts and depressions formed in the Triassic and the NE‐trending uplifts and depressions formed in the Jurassic. The faulted‐uplifts and faulted depressions controlled by NE faults emerged in the Cretaceous. Because the middle crust is a low‐velocity layer and its deformation is mainly ductile, which is completely different from the upper and lower crust, it is thickened and has low velocity in uplifted areas, whereas its thickness decreased and has high velocity in depressions. The overall strength of the crust is reduced in places of thick middle crust, where faulting and deformation are easy to occur in later tectonic movements, thus affecting the occurrence of present earthquakes in the study region.

Ages of Zircons from Basalt of Erdaogou Formation and Diabase Dyke Swarms in Northern Liaoning

The drainage area of Fanhe River around the Tieling City in the northern part of Liaodong Peninsula, is located in the north of the Tancheng-Lujiang fault zone, and belongs to the northeastern end of North China Block in the Sino-Korean plate. In this area, there is huge-thick basalt (Erdaogou Formation) and diabase dyke swarms, which are thought to be Mesoproterozoic basic magmatism. By means of zircon dating with sensitive high-resolution ion microprobe (SHRIMP), the eruption time of the Erdaogou Formation basalt is considered to be 36.4 ± 1.8 Ma, the Eocene Epoch. The emplacement time of the diabase swarms is considered to be 93.5 ± 1.4 Ma, the Late Cretaceous. The basic dyke swarms and basalts in the northern Liaoning were determined as Mesozoic and Cenozoic, respectively. This shows that the northern boundary that divides North China Block and Jiao-Liao-Korean Block within Sino-Korean Plate (i.e. the northern part of the Tancheng-Lujiang fault zone), was in a stretch-tensile tectonic environment in EW direction in Late Cretaceous. In addition, this tectonic environment resulted in the intrusion of the diabase swarms. In Paleogene Period, the stretching direction was changed to near SN, and the formation of the stretching tectonics led to the eruption of the huge-thick Erdaogou Formation basalt. The new SHRIMP zircon U-Pb ages in this article does not support the traditional opinion that the Erdaogou Formation basalt was formed in Mesoproterozoic.

Cack-Handed Design Design-Centred Approaches to Process and Product for Sustainability

ABSTRACTNew directions in design are exploring a variety of contemporary issues that are challenging conventional assumptions in the design and production industries. The artefacts emerging from these new, essentially design-centred, directions are often conceptual in nature and, judged against current industrial design norms, sometimes appear to be rough-and-ready and imprecise. However, they are also highly creative, inspiring and, in their process of production, frequently more sustainable. This paper provides an overview of these new directions and discusses their relevance and contribution in broadening our understandings of the potential of product design. The work of various designers is discussed and illustrated, and this is supplemented with a series of design explorations, conducted by the author, that address various criteria related to design for sustainability (DfS).

Structural identification for post-earthquake safety analysis of the Fat i ̇ h mosque after the 17 August 1999 Kocael i ̇ earthquake

This paper presents the results of the structural identification of a historical structure damaged during the 17 August 1999 Kocaeli earthquake. Results of the structural models and methods are cross-validated in order to identify the reliable dynamic characteristics. Spectral analysis of the eight structural points yields average peak frequencies, respectively at around 2.5, 3.5, 4.3, 5.3 Hz and so on for NW–SE direction. Similarly for the SW–NE direction, peaks are seen at around 2.6, 3.2, 4.5–5 Hz with small differences in amplitudes between different structural points. Among the stations, station 3 behaves differently than the other observation points in low and high frequency regions indicating that the data recorded at station 3 should be examined in more detail. In parametric analysis, (a) the SDOF system as an SISO-ARX model, and (b) the MDOF system as a MIMO-ARX model are adopted and modal deformations are obtained using a state-space model with the OKID technique. The SDOF model captures the important peak frequencies with sufficient accuracy, but magnitudes are arguably small. In MDOF model, responses at the crown stations 1, 2, 3, and 4 display almost the same peak magnitudes at the same frequency, 2.51 Hz for NE–SW direction, but station 3 (which possesses smaller peak amplitude at a smaller frequency, 2.2 Hz) is exceptional and indicative of an anomaly. Similar conclusion with different peak frequency for NE–SW direction is also inferred from the SISO and Spectral analyses, when compared. Station 3 among the crown stations exceptionally yields peak frequency at 1.8 Hz in spectral analysis and around 1.8 Hz in SISO analysis. Natural frequencies of the structure estimated by SDOF and MDOF systems are close to each other, and thus, they can be accepted as global properties of the structure, except station 3. Such inconsistency implies that, for indicative anomaly, there might be a practical avenue through the evaluation of the first mode estimated by spectral, SDOF and MDOF models for a structure with the members of equal importancy in global dynamic behavior and symmetrical in plan and in elevations. Calculated elastic response spectrum of the Fatih record has larger amplitudes at the period of 0.55 s (with broadband characteristic) and larger than the amplitudes of the design spectrum with 10% probability of excedance in 50 years (for new constructions) for North–South direction. These larger local peaks at 0.55 s; (1) verify the 1.8 Hz of the fundamental frequency of the local ground and (2) suggest that, as the minimum requirements for the earthquake resistant design of buildings, in accordance with the strengthening applications in current seismic design code, the 2% probability of exceedance of the 5% damped elastic design acceleration spectrum within a period of 50 years is adequate. First mode of the structure, 2.4 and 2.5 Hz for NS and EW directions respectively, falls into the range of the dominant broadband period of the seismic loading. Such a match points out the resonance possibility, which might have occurred during the earthquake. The duration of the earthquake and following shocks of many small earthquakes in addition to the resonance might be the key contributors to the damage.

Kinematic modifications after surgical correction of equinovarus foot deformity in chronic hemiplegic adults

nertia during the pivot phase. The actual pivot phase required hree specific power phases in the transverse plane (A2T, 2T, H2T), which provided rotational power to displace the oG toward the new direction. The rotational power at the nkle appears to have been a result of a counter movement uring the deceleration phase, which resulted in an absorption 1T phase prior to the generation A2T phase. The timings of he transverse power peaks suggest that rotation was coming own the kinetic chain initiated from the hip. However, it is robable that the upper body segments lead the pivot [1]. The ipsilateral crossover turn did not require increased uscular demand during the turn phase, as there was no pivot hase suggesting the turn was a result of a fall rather than by ny active means. Because there was no pivot and the foot as rooted to the ground, to complete the crossover, an H3T eneration phase externally rotated the hip/pelvis toward the ew direction.

Multi-scale wavelet separation of aeromagnetic anomaly and study of faults in Beijing area

In this paper, through a multi-scale separation of the aeromagnetic anomaly by wavelet transform technique, we reprocessed the aeromagnetic data collected 20 years ago in Beijing area and analyzed the aeromagnetic anomaly qualitatively, integrating geological structure features in the area. In particular, we studied the spatial distributions of the two main faults called Shunyi-Liangxiang fault and Banqiao-Babaoshan-Tongxian fault, which have cut and gone through the central Beijing area striking in NE and EW directions, respectively. The influences of these two faults on the earthquakes have also been discussed briefly.

Crustal structure across the Colorado Basin, offshore Argentina

SUMMARY The geology of the wide shelves surrounding the South Atlantic is closely linked to the kinematics and history of the opening of the ocean. However, several wide sedimentary basins, which developed along the margins show peculiarities that are not yet understood in the context of the evolution of the South Atlantic. The Colorado Basin, a wide sedimentary basin on the broad shelf of Argentina, extends in EW direction. The basin’s evolution oblique or orthogonal to the continent‐ocean boundary indicates that it is not a product of simple progressive extension and crustal thinning. In addition a basement high, paralleling the continental margin and separating the Colorado Basin from the deep-sea basin is a common interpretation. These findings are hardly in accordance with the idea that the Colorado Basin is an extensional basin that developed in conjunction with the early E‐W opening phase of the South Atlantic in the Late Jurassic/Early Cretaceous. The composition, type, and structure of the basement, key points for the evaluation of the basins evolution, are widely speculative. In this context multichannel seismic reflection data from the Argentine Shelf and a 665-kmlong onshore‐offshore refraction profile, running across the Colorado Basin onto the coast are discussed in combination with gravity data. The stratigraphy for the sedimentary successions was adopted from the literature and the reflection seismic marker horizons formed besides the interval velocities the input for the starting model for refraction seismic traveltime modelling. The modelling strategy was an iterative procedure between refraction seismic traveltime and gravity modelling. The preparation of the density models was coarsely orientated on published velocity‐density relations. The modelling results are in favour of a continuation of the main onshore geological features beneath the sedimentary infill of the Colorado Basin. We interpret the basement along the line from west to east as offshore continuation of the Ventana Hills, the

Shear Wave Splitting and the Features of the Crustal Stress Field in the Capital Circle

AbstractIn recent years, much attention has been paid to the shear wave splitting caused by cracked medium. In this study we investigated the S‐wave splitting at the stations in the Capital Circle from local event data recorded by the permanent and movable seismic network. This presentation shows the fast polarization directions and the maximal compressive stress direction at the stations in the Capital Circle. The 2‐D numerical modeling by the finite element technique demonstrates that the crustal stress field of the Capital Circle can be separated into the NE trending regional stress field and the NW trending local stress field controlled by the Zhangjiakou‐Penglai faults. The direction of the maximal principal compressive stress nearby Beijing and Tianjin is toward NE60° ~ 70°, and that nearby Tangshan and its eastern side is toward the EW direction. For the local stress field, the direction of the maximal principal stress is toward 120° ~ 130°, which is roughly parallel with the strike of the Zhangjiakou‐Penglai faults. Our numerical modeling demonstrates that the local crustal stress field in the Capital Circle is caused mainly by the Zhangjiakou‐Penglai faults.

Strainmeters at Moxa observatory, Germany

Since 1997, two quartz tube strainmeters at the Geodynamic Observatory Moxa, located 30 km south of Jena, are used to observe long-period horizontal deformation signals. Both strainmeters are 26 m long with orientations NS and EW and are installed in a gallery. To this system a third component was added in 1999, which connects the ends of the quartz tubes diagonally. This component is realised as a laser strainmeter, running through a 38 m long horizontal borehole. The first data analyses show high signal-to-noise ratios for the tidal frequencies and also the free oscillations caused by the Sumatra earthquake in December 2004 are clearly detectable. It can be shown that the quartz strainmeter extending in EW direction generally contains significant more noise induced by barometric pressure than the NS-component. The laser strainmeter record shows strong influences of changing barometric pressure, due to the fact that the beam does not run in a vacuum. This influence is reduced in the higher frequencies by sealing the ends of the horizontal borehole with high quality glass. In addition, the observations are clearly temperature dependent and the influence of rainfall could be verified by two irrigation experiments.

Crowded field 3D spectroscopy of LBV candidates in M 33

We present integral field spectroscopy of the LBV candidate stars B 416 and v 532 in the local group galaxy M 33. B 416 is surrounded by an elongated ring-like nebula, which has a projected radius of pc. From the datacube we create ionization and radial velocity maps of the nebula. The excitation of the gas decreases towards the outer part of the ring, while the inner part of the nebula is filled with a more excited gas. In the EW direction the ring is seen to expand with a maximum projected velocity amplitude of about 40 km s-1. The eastern part approaches the observer. We estimate the nebula dynamical lifetime ∼ years. It could be a residual MS bubble, which indicates a main-sequence or pre-LBV status of the star. We classify B 416 as an “iron star” or B[e]-supergiant. In v 532 an elongated nebula has been marginally detected. The total projected size of the nebula along the main axis is 30 pc, and the total radial velocity gradient is km s-1. v 532 exhibits both strong photometric and spectral variability. At the time of our observations it was in an intermediate brightness state with a rich nitrogen spectrum. We classify v 532 as an LBV, showing LBV Ofpe/WN transitions. We stress the importance of integral field spectroscopy as the optimal technique for studying nebulae and the evolution of LBV-like stars in nearby galaxies.

Tomographic Determination of 3-D Crustal Structure in Changbaishan-Tianchi Volcano Region

Using reflection traveltimes of P wave from the 3-D deep seismic sounding experiment carried out in Changbaishan-Tianchi volcano region, we have reconstructed 3-D crustal interfaces and crustal velocity images by seismic tomography technique. The interface images show that the crustal depth increases generally from NW to SE, the Ma'anshan-Sandaobaihe and Fu'erhe-Hongqihe faults are two main deep faults in the region. Variation in crustal thickeness is especially obvious on both sides of Ma'anshan-Sandaobaihe fault, which runs across Tianchi crater in NNE direction. This indicates that there is an abrupt variation belt of crustal thickness or a deep crustal fault at this position. The velocity images show that an obvious low-velocity anomaly of P wave exists around Tianchi at the depth of 10km. It becomes a nearly SN-oriented low-velocity anomalous strip at the depth of 15km, which extends about 80~90km in SN direction and 30~40km in EW direction. With the increase of depth, the low-velocity anomalous strip can still be found on the west side of Tianchi, but with smaller scale. At this point, it becomes more concentrated and presents higher perturbation. This changing image of P-wave velocity anomaly illustrates the spatial distribution of the magma system under Tianchi volcano to a certain extent.

Assessment of predictions of the response of the Hualien containment model during forced vibration tests

Blind predictions for the response of the 1/4-scale reinforced concrete Hualien (Taiwan) containment model during forced vibration tests are compared with the observed data. The predictions obtained by the CLASSI approach reflect the experimental conditions prior to and after backfill of the soil surrounding the embedded foundation. The experimental data show a strong and unexpected coupling between the response in the NS and EW directions which is not present in the results for the axisymmetric theoretical models. Also, significant differences can be seen between the experimental responses in the two orthogonal horizontal directions which minimize cross-axis coupling. Although these differences are not accounted for in the theoretical models, the discrepancies between predictions and observations are within the uncertainty of the structural and geotechnical data. The obtained differences between predictions and observations give an excellent measure of the prediction error that can be expected in this type of analysis from uncertainty in the data. A detailed assessment of the initial structural and geotechnical data based on extensive comparisons with the results of previous identification studies is also presented. Finally, comparisons between the observed response and calculations based on revised models for the structure and the soil show that current methods of analysis can account accurately for the observed response.

Lateral variations of Pn velocity and anisotropy in Taiwan from travel-time tomography

In this study, the P arrivals of 1726 ray paths with the epicentral distances longer than 200 km from 539 earthquakes that occurred in Taiwan are used to investigate the variation of Pn velocity. The results show that the lateral variation of Pn velocity in Taiwan is quite similar to the pattern of gravity anomaly and strongly related to several features of Taiwan’s geological structure. The crust is a little thicker (about 39 km) in the Central Range and somewhat thinner toward the east and west. A relatively thin crust (about 35 km) is obtained in the area of Peikang High; however, an unexpected thick crust of greater than 40 km is also found at the corner of southwestern Taiwan. The degree of anisotropy of Pn velocity is found less than 10% and the fast direction is generally in the EW direction. This direction is parallel to the axis of compressional stress or the direction of plate motion, indicating that the anisotropy results from the deformation of the upper mantle.

Current deformation of the Himalaya–Tibet–Burma seismic belt: inferences from seismic activity and strain rate analysis

A new measure of seismic activity in a region is defined, which is based on the concept of integrated fault surface area of earthquakes in the region. Using this concept, we analyze the Harvard CMT data of the Himalaya–Tibet–Burma seismic belt to estimate the relative proportions of seismic activity corresponding to reverse, strike-slip and normal faulting in the region. Further, strain rates are computed through summation of moment tensor elements of earthquakes. The study indicates that the deformation patterns of the Himalaya and the adjoining Tibetan plateau regions are distinct. For instance, the seismic activity of the reverse fault category changes from 93% in the Himalaya to a mere 2% in Tibet, which is dominated instead, by strike-slip faulting (59%). Strain rate computation indicates predominant crustal thickening in the Himalaya with a clear transition to crustal thinning in the Tibetan plateau region, just across the Indus-Tsangpo suture zone where EW extension is the predominant mechanism. A model of a thinning seismic upper crust in the EW direction decoupled from a thickening aseismic lower crust, both in equilibrium, in the Tibetan plateau, is proposed. In the Burmese arc region, crustal thickening is indicated, but coupled with NS compression. The observed seismic activity is predominantly of the strike-slip type (56%), uncharacteristic of subduction zones, which generally display up to 75% of seismic activity of the reverse fault category. This has implications for Indian plate motion along the Burmese arc, rather than in the direction of the subducted slab.