Geodetic Models Research Articles

Geological slip rates along the North Anatolian Fault in the Marmara region

Reliable piercing points on both sides of the Sea of Marmara enabled us to obtain an estimate of the slip‐rate over time scales of 10–15 ka on different fault strands of the North Anatolian Fault (NAF) system. We analyzed geomorphic features in the gulfs of Izmit, Gemlik (Sea of Marmara) and Saros (NE Aegean Sea), which were passively displaced by the NAF strands after their abandonment related to the post‐glacial sea level rise. Results for the main northern strand, consistently similar on both sides of the Marmara pull‐apart, are in the order of 10 mm/yr, about one half of that expected from geodetic measurements and accepted plate‐tectonic models. In the southern branch of the NAF, the estimated rate of ∼4 mm/yr is only slightly higher than that given by geodetic models. Our findings have implications for both neo‐tectonic reconstructions of the submerged portion of the NAF system, and fault interactions and seismic hazard estimates in the Marmara region. They suggest that, either the total Anatolia/Eurasia plate motion is more diffuse than previously reported, or geodetic data are not representative of the geological time‐scale deformations. Moreover, they suggest that a significant amount of stress is accommodated along the southern strand of the NAF system, on which the last large (M ≈ 7) earthquakes dates back to 1419, 1855 and 1863 AD.

The SISMA prototype system: integrating Geophysical Modeling and Earth Observation for time-dependent seismic hazard assessment

An innovative approach to seismic hazard assessment is illustrated that, based on the available knowledge of the physical properties of the Earth structure and of seismic sources, on geodetic observations, as well as on the geophysical forward modeling, allows for a time-dependent definition of the seismic input. According to the proposed approach, a fully formalized system integrating Earth Observation data and new advanced methods in seismological and geophysical data analysis is currently under development in the framework of the Pilot Project SISMA, funded by the Italian Space Agency. The synergic use of geodetic Earth Observation data (EO) and Geophysical Forward Modeling deformation maps at the national scale complements the space- and time-dependent information provided by real-time monitoring of seismic flow (performed by means of the earthquake prediction algorithms CN and M8S) and permits the identification and routine updating of alerted areas. At the local spatial scale (tens of km) of the seismogenic nodes identified by pattern-recognition analysis, both GNSS (Global Navigation Satellite System) and SAR (Synthetic Aperture Radar) techniques, coupled with expressly developed models for interseismic phase, allow us to retrieve the deformation style and stress evolution within the seismogenic areas. The displacement fields obtained from EO data provide the input for the geophysical modeling, which eventually permits to indicate whether a specific fault is in a “critical state.” The scenarios of expected ground motion (shakemaps) associated with the alerted areas are then defined by means of full waveforms modeling, based on the possibility to compute synthetic seismograms by the modal summation technique (neo-deterministic hazard assessment). In this way, a set of deterministic scenarios of ground motion, which refer to the time interval when a strong event is likely to occur within the alerted area, can be defined both at national and at local scale. The considered integrated approach opens new routes in understanding the dynamics of fault zones as well as in modeling the expected ground motion. The SISMA system, in fact, provides tools for establishing warning criteria based on deterministic and rigorous forward geophysical models and hence allows for a well-controlled real-time prospective testing and validation of the proposed methodology over the Italian territory. The proposed approach complements the traditional probabilistic approach for seismic hazard estimates, since it supplies routinely updated information useful in assigning priorities for timely mitigation actions and hence it is particularly relevant to Civil Defense purposes.

Estimation of the Variance Components in Various Covariance Matrix Structures

This article describes the procedure of obtaining variance component estimates with the Minimum Norm Quadratic Unbiased Estimator (MINQUE). Using the examples of simulated measurements, variance components are estimated in geodetic two-dimensional network models. The efficiency of the estimators was tested using simulated data in three different structures of variance component models. Additive, group and mixed models were analyzed using distance and direction measurements, and the efficiency of the estimator was analyzed in all three cases, focusing in particular on the impact of various ratios of the initial variance components and geodetic network characteristics on the variance components estimation.

Design Model of the Tunnel Axis and its Algorithm Implementation

With a large number of construction projects building in urban rail construction, it’s very necessary for researching on the construction axis. Construction axis of the subway is consisted of line segment, circular arc segment and transition curve. The paper introduces design models and algorithms of the tunnel boring machine (TBM) axis (DTA). By analyzing the DTA characteristics of each curve, summing up their general characters, we ultimately make a unified common algorithm and geodetic coordinate calculation model of the design axis in horizontal and vertical planes. It will be very useful for the process of underground construction.

Reconciling geologic and geodetic model fault slip-rate discrepancies in Southern California: Consideration of nonsteady mantle flow and lower crustal fault creep

AbstractIn Southern California, slip rates derived from geodesy-constrained elastic models are lower than geologic rates along the Mojave and San Bernardino segments of the San Andreas fault and the Garlock fault. In contrast, the summed geodetic rate across the Mojave eastern California shear zone (ECSZ) is significantly higher than the summed geologic rate. We show that geodetic and geologic slip rates in Southern California can be reconciled using a viscoelastic earthquake cycle model that explicitly incorporates time-dependent deformation due to nonsteady interseismic fault creep in the lower crust and viscous flow in the upper mantle. To reconcile geologic and geodetic model rates, our model requires that the southern San Andreas fault and the Garlock fault are in the late stages of the earthquake cycle, resulting in lower current deformation rates than the cycle-averaged rate. Our model implies that the ECSZ and the San Jacinto faults are in the early stages of the earthquake cycle, resulting in high current deformation rates.

EGU 2011: Geodetic and inundation models of the Tohoku earthquake and tsunami

At the European Geosciences Union meeting in Vienna, Don Dingwell, the EGU president, introduced the session on the March 2011 Tohoku earthquake as the geoscientific community's way ... At the European Geosciences Union meeting in Vienna, Don Dingwell, the EGU president, introduced the session on the March 2011 Tohoku earthquake as the geoscientific community's way ...

Aftershock Distribution as a Constraint on the Geodetic Model of Coseismic Slip for the 2004 Parkfield Earthquake

Several studies of the 2004 Parkfield earthquake have linked the spatial distribution of the event’s aftershocks to the mainshock slip distribution on the fault. Using geodetic data, we find a model of coseismic slip for the 2004 Parkfield earthquake with the constraint that the edges of coseismic slip patches align with aftershocks. The constraint is applied by encouraging the curvature of coseismic slip in each model cell to be equal to the negative of the curvature of seismicity density. The large patch of peak slip about 15 km northwest of the 2004 hypocenter found in the curvature-constrained model is in good agreement in location and amplitude with previous geodetic studies and the majority of strong motion studies. The curvature-constrained solution shows slip primarily between aftershock “streaks” with the continuation of moderate levels of slip to the southeast. These observations are in good agreement with strong motion studies, but inconsistent with the majority of published geodetic slip models. Southeast of the 2004 hypocenter, a patch of peak slip observed in strong motion studies is absent from our curvature-constrained model, but the available GPS data do not resolve slip in this region. We conclude that the geodetic slip model constrained by the aftershock distribution fits the geodetic data quite well and that inconsistencies between models derived from seismic and geodetic data can be attributed largely to resolution issues.

Comment on "The 28 December 1908 Messina Straits Earthquake (Mw 7.1): A Great Earthquake throughout a Century of Seismology" by N. A. Pino, A. Piatanesi, G. Valensise, and E. Boschi

The recent paper “The 28 December 1908 Messina Straits Earthquake ( Mw 7.1): A Great Earthquake throughout a Century of Seismology” by Pino et al. (2009) provides a review of the observations, early studies, and main accomplishments in the investigation of the source of the 1908 Messina Straits earthquake. Figure 9 in Pino et al. (2009) is the main reason for this comment. The authors assert that the figure shows the slip distribution along-strike of the fault resulting from various studies, including Amoruso et al. (2002). In fact, they compare the seismic moment per unit fault length (shown as an equivalent along-strike slip distribution under the assumption of uniform along-dip slip distribution on a 20-km wide fault) obtained by Pino et al. (2000) from seismic data with the maximum slip along each section of the distributed-slip fault resulting from different geodetic models. Here we show that Figure 9 in Pino et al. (2009) is inconsistent and misleading, because incomparable quantities are compared. Before we address this point, we will discuss the reference in Table 2 of Pino et al. (2009) to the size (100 × 30 km2) of the variable-slip fault of Amoruso et al. (2002), clarifying its real meaning through a short summary of our computation procedure. We also report the main results in Amoruso et al. (2006), omitted in Pino et al. (2009). In Amoruso et al. (2002) we performed a joint inversion of P -wave first-motion polarities and geodetic data (leveling lines along the Calabrian and Sicilian sides of the Straits) under the assumption that uplifts are uncorrelated experimental data. The static baseline corrections for leveling lines were additional free parameters of the model. Fault slip was at first assumed uniform, then independent in a small set of coplanar subfaults sharing the same rake angle (see Figure …

Recent rift-related volcanism in Afar, Ethiopia

Rift zones are the most common magmatic environment on Earth. However opportunities to observe active rifting are rare, and consequently the volcanological characteristics of rift systems are not well understood. An ongoing phase of magmatic rifting along a section of the Red Sea system in Afar, Ethiopia, presents an exceptional opportunity to constrain relationships between volcanism and crustal growth. Here, by integrating analyses of satellite images (i.e. MODIS, OMI, ASTER, and ALI) with field observations, we characterise two recent (August 2007 and June 2009) basaltic fissure eruptions in Afar and evaluate the role and significance of volcanism in the rifting process. Both events were brief (36–72 h) and erupted 4.4–18 × 10 6 m 3 of lava from a fissure system 4–6.5 km in length. Data from the spaceborne Ozone Monitoring Instrument (OMI) suggests total SO 2 emissions for each eruption of 26 ± 5 kt (2007) and 34 ± 7 kt (2009), consistent with complete degassing of the erupted magma volumes. Using geodetic models for the intrusive activity in Afar we estimate the partitioning of magma between intrusive and extrusive components, up to July 2009, to be ∼ 180:1. Comparing the first-order volcanic characteristics and the intrusive–extrusive volume balance for the Afar volcanism with data from the 1975–1984 Krafla rifting cycle (Iceland) suggests that the volcanic flux in Afar will rise significantly over the next few years as the stresses are increasingly relieved by dyking, and subsequent dykes are able to propagate more easily to the surface. As a consequence, basaltic fissure eruptions in this section of the Afar rift will become of increasing large magnitude as the rifting event matures over the next 5–10 yr. Using available models of magmatic rifting we forecast the likely size and location of future eruptions in Afar.

GPS Tracings – Personal Cartographies

Jeremy Wood, places, code and GPS are the protagonists in his personal cartographies. He plots the journeys, bicycles, boats, planes and his two feet provide him mobility, and geography is the precept, all of which are mediated by the communication infrastructure. Land, water, air and the engineered environment of places determine the routes, are the medium within which his body moves and are the settings where he performs his traces. Time, location and established measurement standards, along with geodetic models, radio signals, software, the language of culture and place, encode the narrative voice. GPS is his cartographic rendering tool: it is what points, traces, locates and recounts. Cartography is his narrative mode: it is that which conveys his personal narrative. This article is about a series of conversations mediated by telephone, Skype, email and online chat functions. We discussed Wood's personal cartographies, how these journeys tell him where he is, has been and potentially where he is going. These are personal cartographies, the result of individual journeys that he is assembling. His GPS tracings make us privy to his personal data, which tell us something about him while questions about science, cartography and technology also become conspicuous. The focus is on the Data Cloud outdoor installation, the Meridian performance and Lawn Mowing experiments. Wood's work is playful, yet it also critically foregrounds the fallacy of technological accuracy and the imprecision of stories. Where he is and where things are positioned are inaccurate from a GPS point of view, since GPS is engineered imprecision. This lack of specificity changes the location of things in space ever so slightly, but just enough to confound physical reality as we see in the Data Clouds outdoor installation. However, are stories ever definitive accounts of an experience? And what of the models by which we understand the world? What if we are between spatial models and some spaces are nowhere to be seen? Does that mean the place does not exist? What does it mean to be there but lost in space? What does it mean for a place to exist in the first place? His Meridian performance of the Herman Melville quote 'It is not down in any map; true places never are' elucidates this special conundrum in both literal and metaphorical terms. He traces the words along two meridians drawn according to two different but scientifically approved mathematical models of the earth, GMT and GRS80. Ironically, true places are written in Greenwich Park, the very same location where time and space were established as a standard in 1884.

Split Estimation of Parameters in Functional Geodetic Models

The method of estimation presented in the paper is based on the assumption that every measurement result can be a realization of either of two different, random variables (differing from each other in expected values). Supposing it, the functional model AX y v − = is split into two competitive ones α α AX y v − = and β β AX y v − = , that concern the same vector of observation y (A is a common coefficient matrix, α v and β v are competitive vectors of random errors, α X and β X competitive parameter vectors, respectively). The estimation process proposed here is based on the principle of crossing (mutual) weighting of competitive random errors i vα and i vβ (concerning the same observation i y ). That important rule is realized with such convex weigh functions ) ( β α v w and ) ( α β v w that: ) ( min ) ( sup α β β α δ α β v w v w v v v ⇔ ≤ and ) ( min ) ( sup β e α β δ β α v w v w v v v ⇔ ≤ , where α β δ v v v − = . According to the above principle and referring to the M-estimation theory, the following optimisation problem: ∑ i i i v w v ) ( min 2 β α α α X and ∑ i i i v w v ) ( min 2 α β β β X , will be formulated and solved in the paper. The proposed method is essential extension of M-estimation class. However, its practical application is not limited to a robust estimation of the parameter X ( α X estimator) and extended with estimator β X (concerning outliers). The presented method can be also applied to a joint adjustment of two observation sets measured in two, different epochs. Differences between competitive estimates α X and β X can indicate displacements of network points. The paper presents some basic, numerical examples that illustrate principles of the split estimation in functional geodetic models.

In situ evidence for dextral active motion at the Arabia–India plate boundary

The Arabia–India plate boundary—also called the Owen fracture zone—is perhaps the least-known boundary among large tectonic plates1,2,3,4,5,6. Although it was identified early on as an example of a transform fault converting the divergent motion along the Carlsberg Ridge to convergent motion in the Himalayas7, its structure and rate of motion remains poorly constrained. Here we present the first direct evidence for active dextral strike-slip motion along this fault, based on seafloor multibeam mapping of the Arabia–India–Somalia triple junction in the northwest Indian Ocean. There is evidence for ∼12 km of apparent strike-slip motion along the mapped segment of the Owen fracture zone, which is terminated to the south by a 50-km-wide pull-apart basin bounded by active faults. By evaluating these new constraints within the context of geodetic models of global plate motions, we determine a robust angular velocity for the Arabian plate relative to the Indian plate that predicts 2–4 mm yr−1 dextral motion along the Owen fracture zone. This transform fault was probably initiated around 8 million years ago in response to a regional reorganization of plate velocities and directions8,9,10,11, which induced a change in configuration of the triple junction. Infrequent earthquakes of magnitude 7 and greater may occur along the Arabia–India plate boundary, unless deformation is in the form of aseismic creep.

Geodesy and relativity

Relativity, or gravitational physics, has widely entered geodetic modelling and parameter determination. This concerns, first of all, the fundamental reference systems used. The Barycentric Celestial Reference System (BCRS) has to be distinguished carefully from the Geocentric Celestial Reference System (GCRS), which is the basic theoretical system for geodetic modelling with a direct link to the International Terrestrial Reference System (ITRS), simply given by a rotation matrix. The relation to the International Celestial Reference System (ICRS) is discussed, as well as various properties and relevance of these systems. Then the representation of the gravitational field is discussed when relativity comes into play. Presently, the so-called post-Newtonian approximation to GRT (general relativity theory) including relativistic effects to lowest order is sufficient for practically all geodetic applications. At the present level of accuracy, space-geodetic techniques like VLBI (Very Long Baseline Interferometry), GPS (Global Positioning System) and SLR/LLR (Satellite/Lunar Laser Ranging) have to be modelled and analysed in the context of a post-Newtonian formalism. In fact, all reference and time frames involved, satellite and planetary orbits, signal propagation and the various observables (frequencies, pulse travel times, phase and travel-time differences) are treated within relativity. This paper reviews to what extent the space-geodetic techniques are affected by such a relativistic treatment and where—vice versa—relativistic parameters can be determined by the analysis of geodetic measurements. At the end, we give a brief outlook on how new or improved measurement techniques (e.g., optical clocks, Galileo) may further push relativistic parameter determination and allow for refined geodetic measurements.

A new 1649–1884 catalog of destructive earthquakes near Tokyo and implications for the long‐term seismic process

In order to assess the long‐term character of seismicity near Tokyo, we construct an intensity‐based catalog of damaging earthquakes that struck the greater Tokyo area between 1649 and 1884. Models for 15 historical earthquakes are developed using calibrated intensity attenuation relations that quantitatively convey uncertainties in event location and magnitude, as well as their covariance. The historical catalog is most likely complete for earthquakes M ≥ 6.7; the largest earthquake in the catalog is the 1703 M ∼ 8.2 Genroku event. Seismicity rates from 80 years of instrumental records, which include the 1923 M = 7.9 Kanto shock, as well as interevent times estimated from the past ∼7000 years of paleoseismic data, are combined with the historical catalog to define a frequency‐magnitude distribution for 4.5 ≤ M ≤ 8.2, which is well described by a truncated Gutenberg‐Richter relation with a b value of 0.96 and a maximum magnitude of 8.4. Large uncertainties associated with the intensity‐based catalog are propagated by a Monte Carlo simulation to estimations of the scalar moment rate. The resulting best estimate of moment rate during 1649–2003 is 1.35 × 1026 dyn cm yr−1 with considerable uncertainty at the 1σ level: (−0.11, + 0.20) × 1026 dyn cm yr−1. Comparison with geodetic models of the interseismic deformation indicates that the geodetic moment accumulation and likely moment release rate are roughly balanced over the catalog period. This balance suggests that the extended catalog is representative of long‐term seismic processes near Tokyo and so can be used to assess earthquake probabilities. The resulting Poisson (or time‐averaged) 30‐year probability for M ≥ 7.9 earthquakes is 7–11%.

Reply to comment by B. S. Sukhija et al. on “Interpreting the style of faulting and paleoseismicity associated with the 1897 Shillong, northeast India, earthquake: Implications for regional tectonism”

[1] The source of the 1897 earthquake is central to longstanding controversies about the genesis of the Shillong Plateau and the shortening of the Indian plate at the foot of the Himalaya. Debate on the location and geometry of the 1897 rupture began during the lifetime of R. D. Oldham, a leading geologist during the British colonial period. For nearly 100 years, the 1897 earthquake was attributed to a hypothetical, north dipping fault proposed to extend from the Himalayan thrust system. Instead, Bilham and England [2001] invoked a south dipping fault, which they called the Oldham fault. They further proposed that the Oldham fault is one in a pair of reverse faults of opposing vergence that raised the Shillong Plateau as a pop-up structure. Our paper [Rajendran et al., 2004], while supporting the south dipping geometry, pointed out that the hypothetical Oldham fault lacks known expression along its supposed trace in the exposed crystalline rocks. We also explored potential alternatives, including a buried fault beneath the Brahmaputra Valley. In his comment, Bilham [2006] defends the Oldham fault by pointing out that the Brahmaputra alternative appears to conflict with old triangulation data. In response, we remind readers that the geodetic model by Bilham and England [2001] is a nonunique solution, which remains unsupported by geology. [2] The model of Bilham and England [2001] is based on two sets of triangulation data of doubtful accuracy The 1898 trigonometrical survey south of the hypothetical Oldham fault, across the Shillong Plateau, failed to meet the triangle closure standards of the Survey of India [Oldham, 1899]. Problems also plagued the postearthquake Assam Valley Triangulation Series, north of the hypothetical fault. Writing for the survey as its superintendent, Bomford [1939, p. 32] of the Royal Engineers stated that the triangulation data from Assam (1859–1937) is suitable for nongeodetic purposes only, provided that ‘‘pairs of stations can be found whose mark-stones can be trusted to have undergone no relative movement.’’ Oldham [1899] speculatively ascribed these errors to postseismic crustal movement. Bilham and England [2001] praised this idea as ‘‘ahead of its time’’ without addressing Bomford’s concerns. [3] If, despite these geodetic uncertainties, the Oldham fault is real, one would expect to see it in the geology and geomorphology of the Shillong Plateau [Rajendran et al., 2004]. To explain the fault’s apparent lack of expression, Bilham proposes that as in the case of the 2001 Bhuj earthquake, the faulting in the 1897 earthquake was blind. The thick sediment-fill in the Kachchh rift favored folding and flexuring above the upper part of the fault rupture in 2001, which occurred on an imbricate thrust fault within the rift [Rajendran et al., 2001]. By contrast, the Precambrian crystalline rocks of the Shillong Plateau are unlikely to inhibit surface rupture, especially on a steep dipping fault (50 ) as proposed by Bilham and England [2001]. Even the small-scale structures that would be expected of a major fault are absent in this region. A recent study by Srinivasan [2003], suggests that only 6–7% of the fractures on the Shillong Plateau strike E-W or ENE-WNW, the direction of the hypothesized Oldham fault. Although the proposed Oldham fault coincides with a change in relief, this change need not represent any faulting. The Shillong Plateau slices across granitic plutons, some of which are evident by remote sensing. Differential erosion along their contacts with the host rocks is known to produce high relief. Bilham’s comment does not acknowledge such geological complexities. Fieldwork by a team including Bilham and two of us (B. P. Duarah and C. P. Rajendran), subsequent to the publication of the papers being discussed here, uncovered no evidence for theOldham fault. By contrast, theDauki fault, conjugate to the Oldham fault, according to Bilham and England [2001], is geologically conspicuous. [4] Like the geodetic evidence used by Bilham and England [2001], gravity and seismic data in this region do not point to a unique tectonic explanation for the 1897 earthquake [Rajendran et al., 2004]. However, while the gravity data do not suggest anything anomalous where the Oldham fault is projected, they give a weak signal farther north [see Rajendran et al., 2004, Figure 4]. The Oldham fault is not apparent, either in our compilation of microseismic data or in a recent larger and better data set (J. R. Kayal et al., Shillong Plateau earthquakes in northeast India region: Complex tectonic model, unpublished manuscript, 2005). As proposed in our paper, this recent TECTONICS, VOL. 25, TC2002, doi:10.1029/2005TC001902, 2006

Reply to comment by R. Bilham on “Interpreting the style of faulting and paleoseismicity associated with the 1897 Shillong, northeast India, earthquake: Implications for regional tectonism”

Reply to comment by R. Bilham on “Interpreting the style of faulting and paleoseismicity associated with the 1897 Shillong, northeast India, earthquake: Implications for regional tectonism”

Megathrust investigations

The devastating SumatraAndaman earthquake of 26 December 2004 was the first giant earthquake to occur in the era of modern space-based geodesy and broadband seismology, and the mass of data collected during the event is now being analysed. A dataset of about 300 observations in the near field area has been used to produce a geodetic model of the rupture that began the event. It was over 1,500 km long and 150 km wide. A striking feature is the abrupt southern termination of the coral uplift, possibly due to a seafloor structural discontinuity.

Strain accommodation in transitional rifts: extension by magma intrusion and faulting in Ethiopian rift magmatic segments

Abstract Active deformation within the northern part of the Main Ethiopian Rift (MER) occurs within approximately 60 km-long, 20 km-wide ‘magmatic segments’ that lie within the 80 km-wide rift valley. Geophysical data reveal that the crust beneath the <1.9 Ma magmatic segments has been heavily intruded; magmatic segments accommodate strain via both magma intrusion and faulting. We undertake field and remote sensing analyses of faults and eruptive centres in the magmatic segments to estimate the relative proportion of strain accommodated by faulting and magma intrusion and the kinematics of Quaternary faults. Up to half the ≤10 km-long normal faults within the Boset-Kone and Fantale-Dofen magmatic segments have eruptive centres or extrusive lavas along their length. Comparison of the deformation field of the largest Quaternary fault and an elastic half-space dislocation model indicates a down-dip length of 10 km, coincident with the seismogenic layer thickness and the top of the seismically imaged mafic intrusions. These relations suggest that Quaternary faults are primarily driven by magma intrusion into the mid- to upper crust, which triggers faulting and dyke intrusion into the brittle upper crust. The active volcanoes of Boset, Fantale and Dofen all have elliptical shapes with their long axes in the direction N105, consistent with extension direction derived from earthquake focal mechanisms. Calderas show natural strains ranging from around 0.30 for Boset, 0.55 for Fantale, and 0.94 for Dofen. These values give extension strain rates of the order of 0.3 microstrain per year, comparable to geodetic models. Structural analyses reveal no evidence for transcurrent faults linking right-stepping magmatic segments. Instead, the tips of magmatic segments overlap, thereby accommodating strain transfer. The intimate relationship between faulting and magmatism in the northern MER is strikingly similar to that of slow-spreading mid-ocean ridges, but without the hard linkage zones of transform faults.

Review of GPS Satellite Surveying, third edition by Alfred LeickGPS Satellite SurveyingJohn Wiley & Sons0-471-05930-7$120

This book is a third edition recently updated to include new developments in global positioning system GPS theory that have occurred since the release of the second edition in 1995. The book highlights high-accuracy GPS positioning and is intended for use by surveyors, civil engineers, transportation engineers, geodesists, geologists, geographers, technicians, and students—basically anyone with a desire to learn how scientists use least-squares adjustments, geodesy, and various physical models to process data collected from existing and future global navigation satellite systems GNSS . The book consists of nine chapters and three appendixes, as well as an extensive list of bibliographic references and an index. Chapter 1 gives the history of GPS and presents a timeline of the major milestones. Chapter 2 discusses such geodetic reference systems as the international terrestrial reference frame, and the international celestial reference frame, and how to go from one to the other. It includes new material on the effects of polar motion, tectonic plate motion, solid earth tides, and ocean loading. It introduces the three-dimensional 3D geodetic model as the preferred, unifying model for combining satellite positioning with classical surveying measurements. It also discusses the geoid and reductions to the ellipsoid. Chapter 3 outlines basic satellite orbit theory such as the Keplerian elements and the major forces that perturb satellite orbits: variations in the earth’s gravity field, the attraction of the sun and moon, and solar radiation pressure. New sections have been added to address eclipse transits and yaw maneuvers by GPS satellites; the planned L2C-, L5-, and M-codes for GPS modernization; the Russian GLONASS navigation message; and the upcoming Galileo satellite system. Chapter 4 contains basically the same comprehensive treatment of least-squares adjustments covered in the second edition: stochastic and mathematical models, variance-covariance propagation, and the mixed adjustment model—together with the special cases of the observation equation and condition equation models, linearization, sequential solutions, minimal and inner constraints, properties of error ellipses, redundancy numbers, internal and external reliability, and data snooping. A short section has also been added on Kalman filtering; this section nicely defines the concepts behind Gauss–Markov processes, white noise, and random walk. Chapter 5 presents the observation equations for the many different types of pseudorange and carrier phase observables used with GPS. It discusses the single-, double-, and triple-differences for the carrier phases and adds new sections that describe the correction for the rotation of the earth during signal transmission and the P1-P2 and C1-P1 code biases needed to compute accurate pseudoranges for GPS. Chapter 6, on the troposphere and ionosphere, has been extensively rewritten to include additional material. The Saastamoinen equations for zenith hydrostatic delay and zenith wet delay are now given, together with the hydrostatic

Comparison of Static, Kinematic and Dynamic Geodetic Deformation Models for Kutlug�n Landslide in Northeastern Turkey

Being the cause of the loss of life and damaging property, landslide is an important natural hazard. Therefore, landslides have to be monitored and preventive measures taken accordingly. In Geodesy, landslides can be determined with static, kinematic and dynamic geodetic models. The aim of this study is to develop a dynamic geodetic model for landslides and compare it with static and kinematic geodetic models. A study area was selected in the Northeastern Black Sea Region of Turkey where landslides are the most effective natural hazard. Movements were determined with static, kinematic and dynamic geodetic models using geodetic, geologic and geophysical measurements made in the study area. Groundwater levels changes were regarded as causative forces in the formulation of the dynamic model. The dynamic model delivered more detailed information (direction, values, velocity, acceleration of movements) about landslide movements. It is possible to formulate more realistic strategies about prevention of landslides by using this information. As a result, it can be suggested that dynamic geodetic models are more useful in landslide studies.