These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

Plate Tectonics: Diverging, Converging, and Transform Boundaries  

NSDL National Science Digital Library

In this lesson, students will learn to distinguish the different layers of the Earth, observe the effects of plate movements, and explore the reasons for earthquakes and volcanoes. They will label and measure the thicknesses of each layer of the Earth (lithosphere, asthenosphere, etc.) and record their results, construct models from sand and clay to illustrate what happens at the three types of plate boundaries (transform, diverging, and converging), and investigate convergent plate boundaries to see which scenarios may create earthquakes and/or volcanoes.

2

Slip partitioning along major convergent plate boundaries  

NASA Astrophysics Data System (ADS)

Along plate boundaries characterized by oblique convergence, earthquake slip vectors are commonly rotated toward the normal of the trench with respect to predicted plate motion vectors. Consequently, relative plate motion along such convergent margins must be partitioned between displacements along the thrust plate interface and deformation within the forearc and back-arc regions. The deformation behind the trench may take the form of strike-slip motion, back-arc extension, or some combination of both. We observe from our analysis of the Harvard Moment Tensor Catalog that convergent arcs characterized by back-arc spreading, specifically the Marianas and New Hebrides, are characterized by a large degree of slip partitioning. However, the observed rates, directions, and location of back-arc spreading are not sufficient to account for degree of partitioning observed along the respective arcs, implying that the oblique component of subduction is also accommodated in part by shearing of the overriding plate. In the case of the Sumatran arc, where partitioning is accommodated by strike-slip faulting in the overriding plate, the degree of partitioning is similar to that observed along the Marianas, but the result is viewed with caution because it is based on a predicted plate motion vector that is based on locally derived earthquake slip vectors. In the case of the Alaskan-Aleutian arc, where back-arc spreading is also absent, the degree of partitioning is less and rotation of slip vectors toward the trench normal appears to increase linearly as a function of the obliquity of convergence. If partitioning in the Alaskan-Aleutian arc is accommodated by strike-slip faulting within the upper plate, the positive relationship between obliquity of convergence and the rotation of earthquake slip vectors to the trench normal may reflect that either (1) the ratio of the depth extent of strike-slip faults behind the trench Z s to the subduction thrust Z t increases westward along the arc, (2) the dip of the subduction thrust increases westward along the arc, or (3) the strength of the subduction thrust decreases westward along the arc.

Yu, Guang; Wesnousky, Steven G.; Ekström, Göran

1993-06-01

3

Partitioning of Oblique Plate Convergence at the Sumatran Plate Boundary  

NASA Astrophysics Data System (ADS)

At the Sumatran plate boundary, the Indo-Australian plate subducts beneath the Sunda block at a rate of ~5-6 cm/yr, in a direction of ~10° oblique to the trench-normal. Such oblique plate convergence is partitioned into subduction along the Sumatran subduction interface and strike-slip motion along the Sumatran fault. The Sumatran GPS Array (SuGAr), first established in 2002 with 6 stations, now has 50 stations. Using the decade-long time series, we have estimated long-term background rates for the SuGAr stations, with simultaneous estimation of a large number of earthquake parameters. By projecting the long-term rates into trench-normal and trench-parallel directions, we are able to separate deformation related to subduction and transform motion, respectively, to first order. For subduction-related trench-normal velocities, we find stations on the Mentawai islands -- where a great earthquake has been forecast for the coming decades -- have almost double the velocity of stations on the Batu islands where low coupling has been proposed. This observation strongly supports the idea that an earthquake on the Mentawai seismic gap is overdue, and the Batu section is likely a weakly coupled barrier between strongly coupled regions to the north and south. For transform-related trench-parallel velocities, we find rates progressively decrease from ~25 mm/yr on islands offshore Sumatra to ~15 mm/yr at the Sumatran west coast, and close to zero in the backarc. We will explore plausible models for the heterogeneous coupling on the Mentawai subduction interface and forearc sliver translation.

Feng, L.; Hill, E. M.; Qiu, Q.; Banerjee, P.; Lubis, A.; Sieh, K. E.

2012-12-01

4

Composite transform-convergent plate boundaries: description and discussion  

USGS Publications Warehouse

The leading edge of the overriding plate at an obliquely convergent boundary is commonly sliced by a system of strike-slip faults. This fault system is often structurally complex, and may show correspondingly uneven strain effects, with great vertical and translational shifts of the component blocks of the fault system. The stress pattern and strain effects vary along the length of the system and change through time. These margins are considered to be composite transform-convergent (CTC) plate boundaries. Examples are given of structures formed along three CTC boundaries: the Aleutian Ridge, the Solomon Islands, and the Philippines. The dynamism of the fault system along a CTC boundary can enhance vertical tectonism and basin formation. This concept provides a framework for the evaluation of petroleum resources related to basin formation, and mineral exploration related to igneous activity associated with transtensional processes. ?? 1992.

Ryan, H. F.; Coleman, P. J.

1992-01-01

5

Segmentation of convergent plate boundary in eastern Taiwan observed by Persistent SAR Interferometry  

NASA Astrophysics Data System (ADS)

Rapid convergence between the Eurasian plate and the Philippine Sea plate in eastern Taiwan consumed around 30 mm^-1 of the 82 mm^-1 of the continuous convergence between these two plates. The force has produced prominent landscape and frequent seismicity along this collisional boundary. Because of the obliquity of the arc-continent collision, the northern part of the Luzon arc collided first with the Eurasian continental margin and the collision propagated southward with the southern tip of Taiwan only emerged very recently. As a result, the convergent rates vary along the strike of the Longitudinal Valley which was designated as the suture of the two collided plates. In this research, we focus on the spatial variation in the surface deformation along the collisional boundary. Nineteen Envisat ASAR radar images from Track 461, frame 3123 and 3141 were used to extract surface deformation signals from the plate suture. We applied PSI (Persistent Scatterer InSAR) to the area of study, which spans from Hualien city to Taitung city, to observe the surface displacements in the Longitudinal Valley. Our investigation indicates that the Longitudinal Valley can be divided into at least three segments in terms of relative changes in ranges between the approaching Coastal Range and the Longitudinal Valley. Comparison between PSI and leveling results indicates that PSI may be slightly under-estimated the magnitude of velocity relative to the ones derived from leveling.

Yen, J.; Chang, C.

2011-12-01

6

Plate Tectonics II: Plates, plate boundaries, and driving forces  

NSDL National Science Digital Library

The distribution of earthquakes and volcanoes around the world confirmed the theory of plate tectonics first proposed by Wegener. These phenomena also help categorize plate boundaries into three different types: convergent, divergent, and transform.

Egger, Anne

2003-03-18

7

Focal Mechanisms at the convergent plate boundary in Southern Aegean, Greece.  

NASA Astrophysics Data System (ADS)

Greece is characterized by high seismicity, mainly due to the collision between the European and the African lithospheric plates and the dextral strike slip motion along the North Anatolia Fault zone and North Aegean Trough. The subduction of the Eastern Mediterranean oceanic plate along the Hellenic Arc under the Aegean microplate along with the accompanied roll back of the descending slab is considered the main tectonic feature of the region (Papazachos and Comninakis 1971; Makropoulos and Burton 1984; Papazachos et al. 2000a, b). The divergent motion between the Aegean block and mainland Europe is indicated by an extension zone in the northern Aegean, with Crete and Aegean diverging from mainland Europe at a rate of about 3.5 cm yr-1 with Africa moving northward relative to Europe at a rate of about 1 cm yr-1 (Dewey et al., 1989; Papazachos et al., 1998; Mc-Clusky et al., 2000; Reilinger et al., 2006). In this tectonically complicated area diverge types of deformation are manifested, in addition to the dominant subduction processes. Aiming to shed more light in the seismotectonic properties and faulting seismological data from the Hellenic Unified Seismological Network (HUSN) were selected and analyzed for determining focal mechanisms using the method of moment tensor inversion, additional to the ones being available from the routine moment tensor solutions and several publications. Thus, 31 new fault plane solutions for events with magnitude M>4.0, are presented in this study, by using the software of Ammon (Randall et al., 1995). For this scope the data from at least 4 stations were used with an adequate azimuthal coverage and with an epicentral distance not more than 350 km. The preparation of the data includes the deconvolution of instruments response, then the velocity was integrated to displacement and finally the horizontal components were rotated to radial and transverse. Following, the signal was inverted using the reflectivity method of Kennett (1983) as implemented by Randall (1994) in order to determine Green's functions. Initially, iterative inversions were performed considering a crude depth interval of 5 km and the relative misfit functions were computed. In a second stage, inversions were performed considering a finer depth interval of 1-2 km around the depth where the lowest misfit was exhibited. During the analysis different velocity models were used (Karagianni et al., 2005; Novotny et al., 2001; Papazachos et al., 1997). This research has been funded by the European Union (European Social Fund) and Greek national resources under the framework of the "THALES Program: SEISMO FEAR HELLARC" project of the "Education & Lifelong Learning" Operational Programme.

Moshou, Alexandra; Papadimitriou, Eleftheria; Drakatos, George; Evangelidis, Christos; Karakostas, Vasilios; Vallianatos, Filippos; Makropoulos, Konstantinos

2014-05-01

8

ConcepTest: EQ and Convergent Boundary Sketch  

NSDL National Science Digital Library

The figure below was drawn by a student to show the relationship between earthquake epicenters (filled circles) and a convergent plate boundary (red line). The figure represents a boundary between an oceanic plate ...

9

ConcepTest: EQ and Convergent Boundary Sketch2  

NSDL National Science Digital Library

The figure below was drawn by a student to show the relationship between earthquake epicenters (filled circles) and a convergent plate boundary (red line). The figure represents a boundary between an oceanic plate ...

10

Anatomy of an Ancient Convergent Plate Boundary in the Depth Range of its Seismogenic Coupling Zone; Insights From Field Studies in the Swiss Alps  

NASA Astrophysics Data System (ADS)

Interplate subduction earthquakes nucleate within the upper part of subduction zones within the seismogenic coupling zones. Since, active subduction zones cannot be directly accessed, only geophysical methods, numerical modeling or physical simulations shed light on these geodynamic settings. Hence, direct investigation of exhumed fossil subduction zones and their comparison with indirectly acquired data from active ones is the most promising approach to the understanding of processes along convergent plate boundaries in the depth range of seismogenic coupling. For this purpose we studied a melange zone within the Central Alps of Europe. The fossil, formerly south to southeast dipping plate boundary zone is sandwiched between the overlying Austroalpine nappes (African plate) and the footwall Penninic/Helvetic nappes (European plate), a setting assembled during Alpine convergent plate motion. Due to large scale tilting of the zone, a continuous outcrop allows the identification of changes with depth within the former subduction channel. Towards the south, where formerly deeper parts of the coupling zone are accessible, overprint of the upper plate basement by Alpine deformation increases, the matrix of the subduction channel, composed of metasediments, exhibits equally increasing metamorphic grade, and the appearance of mylonitic shear zones increases as well. Bulk provenance analysis of some metasedimentary rocks suggests that they may represent turbiditic layers. This matrix contains clasts of different size comprising upper plate basement and metasediments as well as slivers of the oceanic lower plate and its sedimentary cover. The clast size varies from a few cm to hundreds of meters. With increasing metamorphism and deformation both upper plate basement and metasedimentary clasts are strongly mylonitized along their rims. Mylonitic shear zones cut into the clasts and enforce disintegration. Pseudotachylytes as evidence for unstable slip have been found at a limited depth range (app. 3-6 kbar, <350°C) at the base of the upper plate. Metasedimentary clasts and metabasics reveal abundant hydraulic fractures with partly blocky mineralization. Additionally, a vast number of foliation-parallel mineralized veins invade the matrix of the fossil subduction channel. The relationship of these mineralized fractures to seismic faulting has yet to be evaluated. They may mirror dehydration processes during prograde metamorphism within the subduction zone. Rb/Sr isotope signature of 9 lower plate carbonatic samples provide clear indications for the presence of fluids with elevated 87Sr/86Sr ratios in the subduction channel, suggesting that dehydration of continent-derived sediments was the main fluid source. On a larger scale, we compare the distribution of seismicity at the former plate boundary with recent aftershock data from the 1995 Antofagasta earthquake in northern Chile, as well as the Vp/Vs ratios, and reflectivity data obtained along active convergent plate margins with their possible ancient counterparts.

Bachmann, R.; Oncken, O.; Glodny, J.; Kemnitz, H.

2006-12-01

11

Characterizing Plate Boundaries  

NSDL National Science Digital Library

To prepare for this exercise students read about the processes that operate at plate boundaries and how they are related to the distinct patterns of seismicity, volcanism, surface elevations (e.g., ridges versus trenches), and seafloor ages characteristic of different boundary types. During the week the assignment is available online, students have access to: (1) an index map that locates three boundaries they are to study; and (2) four maps from Sawyer's Discovering Plate Boundaries website that provide the data mentioned above. Student tasks are to: (1) document patterns in each type of data along the three targeted boundaries; and (2) use these observations in conjunction with their understandings of the processes that operate along different types of boundaries to decide whether each of the targeted sites is most likely to be a divergent, convergent, or shear boundary. This activity gives students practice in map reading, interpreting the likely tectonic setting of a boundary by pulling together constraints from several types of data, and collaborating with their classmates in an online environment. The activity also provides a foundation for understanding a wide range of phenomena that are discussed later in the semester in the context of plate tectonic processes. Teaching Tips Adaptations that allow this activity to be successful in an online environment Sawyer's Discovering Plate Boundaries is a jigsaw exercise in which students collaboratively develop an empirical classification of plate boundaries by first studying an individual data set (e.g., seismicity) and then working as part of a multidisciplinary team to develop a composite classification for the boundaries of a single plate using several types of data. In order for the classification to be truly empirical, students are not introduced to the "traditional" classification of plate boundaries till the end of the exercise. In adapting this assignment to the online environment I have: (1) asked students to prepare by becoming familiar with the standard classification of plate boundaries and the processes that operate at them; (2) limited their work to three targeted boundaries of different types; and (3) provided guidance about which features to look for in the each data set. I have found that these modifications help online students, who often work alone "on their own schedules", to avoid getting "lost" and frustrated with the assignment and to compensate for the lack of collaborative input they would receive in a classroom setting. Elements of this activity that are most effective The success of this exercise is really seems to depend on how well a student follows the directions. If a student learns about the geologic differences among plate boundaries, makes careful observations, and thoughtfully compares his or her observations to the expected patterns he or she typically does quite well based on answers to the follow-up questions. If, on the other hand, a student simply looks up the types of the targeted boundaries on a map and then attempts to "back out" the observations that he or she thinks should fit, the result is often inconsistency and a poor score on the questions. (I can often tell which approach a student is taking based on the queries they post to the discussion board, but rarely seem to be able to get those who are trying to work backwards through the assignment to change direction.) Recommendations for other faculty adapting this activity to their own course: To date my experience developing an engaging online exercise to help students learn the principles of plate tectonics has only been partly successful. I think that having such an exercise is critical, however, because this topic provides the framework for so much of what we learn in the geosciences. Based on my efforts to adapt elements of Discovering Plate Boundaries to an online environment I would offer three recommendations. (1) Provide examples. Confronted with an unfamiliar map students are sometimes confused when asked to decide if seafloor age, for example, is uniform or variable along the length of a boundary. Showing them what you mean using snapshots from a map can often clear questions like this up quickly. Similarly, for written work a single example that gives them a clear sense of "what you're looking for" and can often head off a lot of questions. (2) Choose the boundaries you ask students to study carefully. The scarcity of documented volcanism along a mid-ocean ridge or the burial of seafloor age belts by sediment along a trench can result in student observations that are correct, but problematic for correctly assessing the nature of a boundary. (3) Stay on top of student questions and comments, and be prepared to make well-publicized "mid-course corrections" if something you thought was clear turns out to be misunderstood. These minor corrections happen naturally in face-to-face classes but can require real diligence to catch and correct in the online environment.

Hirt, Bill

12

Mapping Plate Tectonic Boundaries  

NSDL National Science Digital Library

To prepare for this activity, students do background reading on Plate Tectonics from the course textbook. Students also participate in a lecture on the discovery and formulation of the unifying theory of plate tectonics, and the relationship between plate boundaries and geologic features such as volcanoes. Lastly, in lecture, students are introduced to a series of geologic hazards caused by certain plate tectonic interactions. The activity gives students practices at identifying plate boundaries and allows them to explore lesser known tectonically active regions.

Kerwin, Michael

13

Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models  

Microsoft Academic Search

The oceanic Cocos Plate subducting beneath Costa Rica has a complex plate tectonic history resulting in segmentation. New lines of magnetic data clearly define tectonic boundaries which separate lithosphere formed at the East Pacific Rise from lithosphere formed at the Cocos-Nazca spreading center. They also define two early phase Cocos-Nazca spreading regimes and a major propagator. In addition to these

Udo Barckhausen; Cesar R. Ranero; R. von Huene; Steven C. Cande; Hans A. Roeser

2001-01-01

14

India Plate Motion, Intraplate deformation and Plate Boundary Processes (Invited)  

NASA Astrophysics Data System (ADS)

We use GPS-measured velocities to geodetically constrain India plate motion, intraplate strain, and examine plate boundary deformation and plate interactions around the India plate. Our solution includes 15 GPS velocities from continuously recording stations from within the stable India plate interior that are used to estimate angular velocity of the India plate with respect to its neighbors. We test a two-plate India system divided along the topographically prominent Narmada Son Lineament and find this scenario to be significant only to 89%. Dense station coverage along the Himalayan range front allows us to rigorously test boundary parameterizations and develop a preferred plate boundary model. In our preferred model the Himalayan Range Front accumulates ~50% of the India-Eurasia convergence with as much as 18 mm/yr of slip accumulation along some segments. We compare earthquake slip vector orientations with predicted divergence directions from our preferred model along the India-Somalia plate boundary. We see good agreement between predicted plate directions from our preferred model and the seismological data. Deviations between our model and the slip vectors highlight areas of diffuse oceanic deformation along the plate boundary. We estimate convergence vectors for the relative plate pairs along the Sumatra subduction zone. We test for the transition between Australian plate convergence and India plate convergence along the Sumatra subduction zone and refine the estimated motion of the Burman sliver plate.

Apel, E. V.; Burgmann, R.; Banerjee, P.

2010-12-01

15

Visualizing Earthquakes at Convergent Plate Margins  

NSDL National Science Digital Library

This screenshot shows the Fiji subduction zone, one of the featured convergent margins in this visualization. The visualization shows how earthquakes at this margin occur at depth, and define the slope of the subducting plate. This visualization also includes other examples of subduction zones and continental convergent margins (Himalayas). Click the image to enlarge or view the MP4 movie (MP4 Video 30.3MB Dec20 11). The purpose of this activity is to introduce students to the distribution and characteristics of earthquakes associated with convergent plate boundaries. Students will learn about how the magnitude and distribution of earthquakes at convergent boundaries are related to processes that occur at these boundaries and to the geometry and position of the two converging plates. Because the depth of earthquakes can be difficult for students to visualize in 2D representations, this activity allows students to visualize the 3D distribution of earthquakes within Earth's surface, which is essential for understanding how different types of earthquakes occur in different tectonic settings. Locations featured in the visualization include the Chile-Peru Subduction Zone, the Aleutian Islands, the Fiji Subeuction Zone, and the Himalayas. Talking points and questions are included to use this visualization as part of an interactive lecture. In addition to playing back the visualization, instructors can also download the visualization software and data set and explore it themselves.

Harwood, Cara

16

Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models  

NASA Astrophysics Data System (ADS)

The oceanic Cocos Plate subducting beneath Costa Rica has a complex plate tectonic history resulting in segmentation. New lines of magnetic data clearly define tectonic boundaries which separate lithosphere formed at the East Pacific Rise from lithosphere formed at the Cocos-Nazca spreading center. They also define two early phase Cocos-Nazca spreading regimes and a major propagator. In addition to these sharply defined tectonic boundaries are overprinted boundaries from volcanism during passage of Cocos Plate over the Galapagos hot spot. The subducted segment boundaries correspond with distinct changes in upper plate tectonic structure and features of the subducted slab. Newly identified seafloor-spreading anomalies show oceanic lithosphere formed during initial breakup of the Farallon Plate at 22.7 Ma and opening of the Cocos-Nazca spreading center. A revised regional compilation of magnetic anomalies allows refinement of plate tectonic models for the early history of the Cocos-Nazca spreading center. At 19.5 Ma a major ridge jump reshaped its geometry, and after ˜14.5 Ma multiple southward ridge jumps led to a highly asymmetric accretion of lithosphere. A suspected cause of ridge jumps is an interaction of the Cocos-Nazca spreading center with the Galapagos hot spot.

Barckhausen, Udo; Ranero, Cesar R.; von Huene, R.; Cande, Steven C.; Roeser, Hans A.

2001-09-01

17

Mountain Maker- Earth Shaker (Convergent Boundary: oceanic-continental)  

NSDL National Science Digital Library

The representation depicts plate boundary interactions. The convergent boundary is one part of a larger interactive diagram (the 2nd slider/ arrow from the left), that focuses on an ocean plate pressing against a continental plate. This review specifically addresses the part of the resource dealing with what happens when plates pull apart. The "show intro" link provides instruction for diagram manipulation.

18

Discovering Plate Boundaries  

NSDL National Science Digital Library

Students are initially assigned to one of four maps of the world: Seismology, Volcanology, Geochronology or Topography. They are also given a map of the world's plate boundaries and are asked to classify the boundaries based upon the data from their assigned map. Students are then assigned to a tectonic plate, such that each plate group contains at least one "expert" on each map. As a group, they must classify their plate's boundaries using data from all four maps. Recent volcanic and seismic events are discussed in the plate tectonic context. Has minimal/no quantitative component Uses geophysics to solve problems in other fields

Henning, Alison

19

Front Cover. (Upper) Perspective view of the Juan de Fuca plate showing plate boundaries and the convergence between the Juan de Fuca and North American plates  

E-print Network

and North American plates across the Cascadia subduction zone. (Lower) Map and the Cascadia subduction zone labeled. (Inset) Schematic cross section of the Cascadia of the Workshop 5 Cascadia Subduction Zone 5 Motivation for Offshore Geodesy

Wilcock, William

20

Mapping Plate Boundaries  

NSDL National Science Digital Library

This in-class exercise, profiled on the Starting Point website, is intended to have the students discover plate boundaries based on the uneven geographic occurrence of geologic hazards. The website details the learning goals, teaching notes and materials, and context for this activity. It offers an extensive list of links to additional resources and materials for lecture on geologic hazards and plate tectonics.

Johnson, Rurik

2009-11-12

21

The Role of Serpentinites at Convergent Plate Boundaries: Using New Discoveries to Facilitate the Learning of Major Earth Processes  

NASA Astrophysics Data System (ADS)

A benefit of integrating a vital educational enterprise into a cutting-edge funded research initiative is the ability to bring new scientific discoveries quickly into the classroom without being bound to the textbook publication cycle. A key objective the MARGINS Data in the Classroom project was to facilitate the discovery-to-the-classroom transition of knowledge through the development of Web-deliverable, modular MARGINS “Mini-Lessons”. Some 34 Mini-Lessons are available for classroom use at http://serc.carleton.edu/margins/collection.html, and the development of new Mini-Lessons is a listed Education/Outreach priority of the successor GeoPRISMS Program. An important discovery that arose from the MARGINS Subduction Factory Initiative was the recognition that serpentinites - metamorphically hydrated products of ultramafic rocks rich in serpentine group minerals - are significant constituents of both the mantle wedge and downgoing plate. Serpentines are interesting mineralogically because of their distinctive physical properties, habits and appearance; and for their close affinities with olivine and Mg-rich pyroxenes. Given that serpentines primarily form through the hydration of olivine or Mg-rich pyroxenes, serpentinites constitute a reservoir of subduction-related H2O and entrained trace species in modified mantle rocks of the wedge or slab. As well, serpentine group minerals are interesting rheologically because, as sheet silicates, they can behave in a plastic fashion in rocks that are undergoing deformation, and can thus flow along faults in response to deforming stresses, or be easily entrained in fault rock assemblages along a subduction thrust. Two different MARGINS Mini-Lessons address the issue of serpentinite in subduction zone settings, focusing primarily on the observed occurrences of serpentinite seamounts in the forearc regions of the Mariana subduction system, a MARGINS Subduction Factory Focus Site, and their geochemical and geodynamic implications (e.g., Savov et al 2007); and also on the geophysical inferences of DeShon and Schwartz (2004) and Syracuse et al (2006) as to the presence of abundant serpentinite in different parts of the MARGINS Central American subduction system Focus Site. The Mini-Lesson seeks to lead students through the arguments made in these very recent papers, both through an analysis of the presented data, and through GeoMapApp examinations of bathymetric and geochemical datasets that students can access independently. The instructional approach is one of guided inquiry, with learning goals focused on a deeper understanding of the subduction process through examining its geochemical and geodynamic implications, as well as providing students with experience in the critical reading of the scientific literature and the extraction of useful information from technical papers.

Ryan, J. G.

2010-12-01

22

Seismic gaps and plate tectonics: Seismic potential for major boundaries  

Microsoft Academic Search

The theory of plate tectonics provides a basic framework for evaluating the potential for future great earthquakes to occur along major plate boundaries. Along most of the transform and convergent plate boundaries considered in this paper, the majority of seismic slip occurs during large earthquakes, i.e., those of magnitude 7 or greater. The concepts that rupture zones, as delineated by

W. R. McCann; S. P. Nishenko; L. R. Sykes; J. Krause

1979-01-01

23

Uplift of Zagros Mountains slows plate convergence  

NASA Astrophysics Data System (ADS)

Research has indicated that mountain ranges can slow down the convergence between two tectonic plates on timescales as short as a few million years, as the growing mountains provide enough tectonic force to impact plate motions. Focusing on the convergence of the Arabian and Eurasian plates at the Zagros mountain range, which runs across Iran and Iraq, Austermann and Iaffaldano reconstructed the relative motion of the plates using published paleomagnetic data covering the past 13 million years, as well as current geodetic measurements. They show that the convergence of the two plates has decreased by about 30% over the past 5 million years. Looking at the geological record to infer past topography and using a computer model of the mantle-lithosphere system, the authors examined whether the recent uplift across the Zagros Mountains could have caused the observed slowdown. They also considered several other geological events that might have influenced the convergence rate, but the authors were able to rule those out as dominant controls. The authors conclude that the uplift across the Zagros Mountains in the past 5 million years did indeed play a key role in slowing down the convergence between the Eurasian and Arabian plates. (Tectonics, doi:10.1002/tect.20027, 2013)

Balcerak, Ernie

2013-05-01

24

Metamorphism in Plate Boundary Zones  

NASA Astrophysics Data System (ADS)

Accretionary orogenic systems (AOS) form at sites of subduction of oceanic lithosphere; these systems dominate during supercontinent break-up and dispersal. Collisional orogenic systems (COS) form where ocean basins close and subduction ultimately ceases; these systems dominate during crustal aggregation and assembly of supercontinents. It follows that COS may be superimposed on AOS, although AOS may exist for 100s Ma without terminal collision. AOS are of two types, extensional-contractional AOS in dominantly extensional arc systems, and terrane-dominated AOS in which accretion of allochthonous elements occurs during oblique convergence. On modern Earth, regional metamorphism occurs in plate boundary zones. Blueschists are created in the subduction zone and ultra-high pressure metamorphic (UHPM) rocks are created in collision zones due to deep subduction of continental lithosphere; granulites are created deep under continental and oceanic plateaus and in arcs and collision zones [high-pressure (HP) granulites, ultra-high temperature (UHT) granulites]. In extensional-contractional AOS, basement generally is not exposed, primitive volcanic rocks occur through the history, rift basins step oceanward with time, and a well-defined arc generally is absent. LP-HT metamorphism is dominant, with looping, CW or CCW P-T-t paths and peak metamorphic mineral growth syn-to-late in relation to tectonic fabrics. UHT and HP granulites are absent, and although rare, blueschists may occur early, but UHPM is not recorded. Short-lived contractional phases of orogenesis probably relate to interruptions in the continuity of subduction caused by features on the ocean plate, particularly plateaus. Extensive granite (s.l.) magmatism accompanies metamorphism. Examples include the Lachlan Orogen, Australia, the Acadian Orogen, NE USA and Maritime Canada, and the Proterozoic orogens of the SW USA. At plate boundaries, oblique convergence is partitioned into two components, one directed more orthogonal to the strike of the trench than the convergence vector, and the other directed parallel to the strike of the trench. The orthogonal component is accommodated by subduction, but the margin-parallel component gives rise to block rotations and extension, strike-slip motion, and shortening within the upper plate. In some AOS, it has been argued that `paired' metamorphic belts characterize the metamorphic pattern. Commonly, this is a false construct that results from failure to recognize orogen-parallel terrane migration and the limitations of particular chronological datasets. Whereas a HP-LT (blueschist-eclogite) metamorphic belt may occur outboard, it is generally separated from a LP-HT (And-Sil type) metamorphic belt by a terrane boundary. These are terrane-dominated AOS. In some AOS an additional feature of the orogenic process is ridge subduction, which is reflected in the pattern of LP-HT metamorphism and the magmatism. Granulites may occur at the highest grade of metamorphism in the LP-HT belt, where granite (s.l.) magmatism is common, but UHPM occurs only rarely in the outboard HP-LT belt. Examples include the Mesozoic metamorphic belts of Japan and the North American Cordillera. COS commonly are characterized by syntectonic index minerals that record CW P-T-t paths and Barrovian-type metamorphic field gradients generated by thickening followed by exhumation. However, during the Neoproterozoic, ultra-high temperature granulite facies metamorphism is common in orogens that suture Gondwana, whereas during the Phanerozoic, metamorphism to high-pressure granulite/medium temperature eclogite facies and extreme UHPM conditions commonly occurs and may be more typical of younger COS; examples include the Alpides, the Qinling - Dabie Shan - Sulu orogens, the Variscides and the Caledonides.

Brown, M.

2005-12-01

25

Investigating the deformation of upper crustal faults at the N-Chilean convergent plate boundary at different scales using high-resolution topography datasets and creepmeter measurements  

NASA Astrophysics Data System (ADS)

The Chilean convergent plate boundary is one of the tectonically most active regions on earth and prone to large megathrust earthquakes as e. g. the 2010 Mw 8.8 Maule earthquake which ruptured a mature seismic gap in south-central Chile. In northern Chile historical data suggests the existence of a seismic gap between Arica and Mejillones Peninsula (MP), which has not ruptured since 1877. Further south, the 1995 Mw 8.0 Antofagasta earthquake ruptured the subduction interface between MP and Taltal. In this study we investigate the deformation at four active upper plate faults (dip-slip and strike-slip) located above the coupling zone of the subduction interface. The target faults (Mejillones Fault - MF, Salar del Carmen Fault - SCF, Cerro Fortuna Fault - CFF, Chomache Fault - CF) are situated in forearc segments, which are in different stages of the megathrust seismic cycle. The main question of this study is how strain is accumulated in the overriding plate, what is the response of the target faults to the megathrust seismic cycle and what are the mechanisms / processes involved. The hyper arid conditions of the Atacama desert and the extremely low erosion rates enable us to investigate geomorphic markers, e .g. fault scarps and knickpoints, which serve as a record for upper crustal deformation and fault activity about ten thousands years into the past. Fault scarp data has been acquired with Differential-GPS by measuring high-resolution topographic profiles perpendicular to the fault scarps and along incised gullies. The topographic data show clear variations between the target faults which possibly result from their position within the forearc. The surveyed faults, e. g. the SCF, exhibit clear along strike variations in the morphology of surface ruptures attributed to seismic events and can be subdivided into individual segments. The data allows us to distinguish single, composite and multiple fault scarps and thus to detect differences in fault growth initiated either by seismic rupture or fault creep. Additional information on the number of seismic events responsible for the cumulative displacement can be derived from the mapping of knickpoints. By reconstructing the stress field responsible for the formation of identified seismic surface ruptures we can determine stress conditions for failure of upper crustal faults. Comparing these paleo stress conditions with the recent forearc stresses (interseismic / coseismic) we can derive information about a possible activation of upper crustal faults during the megathrust seismic cycle. In addition to the morphotectonic surveys we explore the recent deformation of the target faults by analyzing time series of displacements recorded with micron precision by an array of creepmeters at the target faults for over three years. Total displacement is composed of steady state creep, creep events and sudden displacement events (SDEs) related to seismic rupture. The percentage of SDEs accounts for >50 % (SCF) to 90 % (CFF) of the cumulative displacement. This result very well reflects the field observation that a considerable amount of the total displacement has been accumulated during multiple seismic events.

Ewiak, O.; Victor, P.; Ziegenhagen, T.; Oncken, O.

2012-04-01

26

The dynamics of convergent boundaries over a convecting mantle  

NASA Astrophysics Data System (ADS)

Attempts to explore the dynamics of convergent boundaries are essentially based on the confrontation of the observed kinematics to the intrinsic dynamic properties of subduction zones. Which often mismatch. On the basis of the mantle flow model of Conrad and Behn (2010), I explore the role of the often neglected basal drag that the flowing mantle exerts underneath each plate. After computing the total torque underneath each plate, I find that (i) the net torque due to basal drag systematically drives plates away from their ridges and towards subduction zones, conformably to the plate circuit; (ii) compressive zones are found where the net drag forces from upper and lower plates are converging, and diverging for extensive zones; (iii) trench migration is dictated by the difference between the upper plate drag force and lower plate drag force. In other words, trenches advance where upper plates pulls the subduction zones and the lower plate pushes it. These results indicate that differences in the dynamics of plate boundaries arise from the global mantle circulation more than the from the local properties of subduction zones. The often neglected drag force thus appears crucial to reconcile the kinematics and dynamics of subduction zones.

Husson, L.

2012-04-01

27

Observe animations of processes that occur along plate boundaries  

NSDL National Science Digital Library

Here are three animations that reveal how tectonic plates move relative to each other at three types of plate boundaries--transform, convergent, and divergent boundaries. Key features such as the asthenosphere are labeled in the animations. In addition, each animation is equipped with movie control buttons that allow students to play, pause, and move forward and backward through each clip. The animation of a transform boundary shows the North American and Pacific plates sliding past one another, while an oceanic plate subducts under a continental plate producing volcanic activity in the convergent boundary animation. Two coordinated movie clips are used to demonstrate what occurs at a divergent boundary from different viewpoints. Copyright 2005 Eisenhower National Clearinghouse

Education, Terc. C.; Littell, Mcdougal

2003-01-01

28

ConcepTest: EQs at Convergent Boundaries  

NSDL National Science Digital Library

The figures below show the location of a plate boundary (red line) and the distribution of earthquake epicenters (filled black circles). The size of the filled circle indicates the earthquake magnitude. Given the ...

29

Effective strength of incoming sediments and its implications for plate boundary propagation: Nankai and Costa Rica as type examples of accreting vs. erosive convergent margins  

NASA Astrophysics Data System (ADS)

The location of the seaward tip of a subduction thrust controls material transfer at convergent plate margins, and hence global mass balances. At approximately half of those margins, the material of the subducting plate is completely underthrust so that no accretion or even subduction erosion takes place. Along the remaining margins, material is scraped off the subducting plate and added to the upper plate by frontal accretion. We here examine the physical properties of subducting sediments off Costa Rica and Nankai, type examples for an erosional and an accretionary margin, to investigate which parameters control the level where the frontal thrust cuts into the incoming sediment pile. A series of rotary-shear experiments to measure the frictional strength of the various lithologies entering the two subduction zones were carried out. Results include the following findings: (1) At Costa Rica, clay-rich strata at the top of the incoming succession have the lowest strength (?res = 0.19) while underlying calcareous ooze, chalk and diatomite are strong (up to ?res = 0.43; ?peak = 0.56). Hence the entire sediment package is underthrust. (2) Off Japan, clay-rich deposits within the lower Shikoku Basin inventory are weakest (?res = 0.13-0.19) and favour the frontal proto-thrust to migrate into one particular horizon between sandy, competent turbidites below and ash-bearing mud above. (3) Taking in situ data and earlier geotechnical testing into account, it is suggested that mineralogical composition rather than pore-pressure defines the position of the frontal thrust, which locates in the weakest, clay mineral-rich (up to 85 wt.%) materials. (4) Smectite, the dominant clay mineral phase at either margin, shows rate strengthening and stable sliding in the frontal 50 km of the subduction thrust (0.0001-0.1 mm/s, 0.5-25 MPa effective normal stress). (5) Progressive illitization of smectite cannot explain seismogenesis, because illite-rich samples also show velocity strengthening at the conditions tested.

Kopf, Achim

2013-11-01

30

The seismotectonics of plate boundaries  

NASA Technical Reports Server (NTRS)

Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

Berger, J.; Brune, J. N.; Goodkind, J.; Wyatt, F.; Agnew, D. C.; Beaumont, C.

1981-01-01

31

The Arabia-India plate boundary unveiled  

Microsoft Academic Search

Since the advent of Plate Tectonics, tectonic plate boundaries were explored on land as at sea for search of active faults where the destructive energy of earthquakes is released. Yet, some plate boundaries, less active or considered as less dangerous to humankind, escaped general attention and remained unknown to a large extent. Among them, the boundary between two major tectonic

M. Fournier; N. R. Chamot-Rooke; M. Rodriguez; C. Petit; P. Huchon; M. Beslier; B. Hazard

2009-01-01

32

Evolution of the Mariana Convergent Plate Margin System  

Microsoft Academic Search

The Mariana convergent plate margin system of the western Pacific provides opportunities for studying the tectonic and geochemical processes of intraoceanic plate subduction without the added complexities of continental geology. The system's relative geologic simplicity and the well-exposed sections of lithosphere in each of its tectonic provinces permit in situ examination of processes critical to understanding subduction tectonics. Its general

Patricia Fryer

1996-01-01

33

Evolution of the mariana convergent plate margin system  

Microsoft Academic Search

The Mariana convergent plate margin system of the western Pacific provides opportunities for studying the tectonic and geochemical processes of intraoceanic plate subduction without the added complexities of continental geology. The system's relative geologic simplicity and the well-exposed sections of lithosphere in each of its tectonic provinces permit in situ examination of processes critical to understanding subduction tectonics. Its general

Patricia Fryer

1996-01-01

34

GEM Plate Boundary Simulations for the Plate Boundary Observatory: A Program for Understanding the Physics  

E-print Network

include understanding how tectonic plates interact, together with an emphasis on understanding the physics of earthquakes. However, the problem of understanding the physics of earthquakes on complex fault networksGEM Plate Boundary Simulations for the Plate Boundary Observatory: A Program for Understanding

Kellogg, Louise H.

35

Statistical tests of additional plate boundaries from plate motion inversions  

NASA Technical Reports Server (NTRS)

The application of the F-ratio test, a standard statistical technique, to the results of relative plate motion inversions has been investigated. The method tests whether the improvement in fit of the model to the data resulting from the addition of another plate to the model is greater than that expected purely by chance. This approach appears to be useful in determining whether additional plate boundaries are justified. Previous results have been confirmed favoring separate North American and South American plates with a boundary located beween 30 N and the equator. Using Chase's global relative motion data, it is shown that in addition to separate West African and Somalian plates, separate West Indian and Australian plates, with a best-fitting boundary between 70 E and 90 E, can be resolved. These results are generally consistent with the observation that the Indian plate's internal deformation extends somewhat westward of the Ninetyeast Ridge. The relative motion pole is similar to Minster and Jordan's and predicts the NW-SE compression observed in earthquake mechanisms near the Ninetyeast Ridge.

Stein, S.; Gordon, R. G.

1984-01-01

36

POINTWISE CONVERGENCE ON THE BOUNDARY IN THE DENJOYWOLFF THEOREM  

E-print Network

POINTWISE CONVERGENCE ON THE BOUNDARY IN THE DENJOY­WOLFF THEOREM PIETRO POGGI­CORRADINI Abstract POGGI­CORRADINI It is natural to ask whether for almost every point # # W the sequence # # n (#) still

Poggi-Corradini, Pietro

37

The Rivera-Cocos Plate Boundary Revisited  

NASA Astrophysics Data System (ADS)

The nature of the boundary between the Rivera and Cocos plates has long been controversial. Early studies (predominantly earthquake studies) suggested that it was a NE oriented left lateral transform boundary. With the collection of multi-beam bathymetric data during the SEAMAT cruise of the N/O Jean Charcot in 1987 it became clear that this early proposal was not entirely correct as no clear transform morphology was observed. Shortly after the SEAMAT campaign, three main proposals emerged to explain this lack of transform morphology. The first two proposals favored the results of earthquake studies over the new multibeam data. The first proposed that the boundary is indeed a left-lateral transform boundary, you just cannot see it. In other words, it was a diffuse boundary and the resolution of the multi-beam data was not sufficient to reveal the associated deformation. The second proposal was that it was an east-west oriented, dextral transform, the proposal being based on the results of an earthquake directivity analysis. The third proposal favored the morphologic data over the earthquake data and proposed that the plate boundary was not a transform boundary, but was instead a divergent boundary, at least near the Middle America Trench in what is now called the EL Gordo Graben. Implicit in this proposal was that the earthquake activity did not reflect plate motions but rather were the result of local stresses. Since 2002, several marine geophysical campaigns have been conducted in the area of the Rivera-Cocos plate boundary with the aim of resolving this debate. During the 2002 BART and FAMEX campaigns of the N/O L'ATALANTE, multibeam bathymetric and seafloor backscatter data were collected along the boundary. During the MARTIC04 and MARTIC05 campaigns of the B/O EL PUMA dense total field magnetic surveys were conducted covering the entire plate boundary. Lastly, the multibeam coverage obtained during the BART/FAMEX campaigns was extended northward during the MORTIC07 campaign of the B/O EL PUMA. In this talk we will present these new data (some of which have already been published) and discuss the constraints that these data impose on the nature of the Rivera-Cocos plate boundary.

Bandy, W. L.; Mortera-Gutierrez, C. A.; Michaud, F.; Ortega Ramírez, J.

2013-05-01

38

MODELING BOUNDARIES BETWEEN CONVERGING FRONTS IN PREHISTORY  

Microsoft Academic Search

We introduce a modeling framework that can be applied to cases of multiple converging fronts during episodes of population expansion and innovation diffusion, referring to two prehistoric case studies known archaeologically (the spread of pottery-making in Europe, and the spread of farming in southern Africa). We model front propagation using Fast Marching methods, drawing on the analogy with crystallization processes

FABIO SILVA; JAMES STEELE

2012-01-01

39

Tectonic mélange as fault rock of subduction plate boundary  

NASA Astrophysics Data System (ADS)

An assemblage of quantitative data sets is examined to evaluate tectonic mélange as a plate boundary fault rocks in subduction zone. The research object is the latest Cretaceous Mugi mélange in the Shimanto Belt, southwest Japan. Systematic age younging from pelagic to terrigenous through hemipelagic sediments is well-documented even though original stratigraphy is disrupted. Systematic shear fabric consistent with ancient plate convergence is reconstructed. The mélange was formed at temperatures of ~ 130-200 °C by cataclastic comminution of sandstone layers accompanied by tensile cracking, and plastic deformation and the dehydration of clayey shale matrix, with subsequent peeling off and underplating of the oceanic basement. The temperature setting for the Mugi mélange indicates around the up-dip limit of the seismogenic zone, therefore includes various fault rocks suggestive of earthquake fault; pseudotachylyte, fluidized ultracataclasite with heating evidence, amorphous silica and so on. These suggest that fluid induced lubrication was dominated. Localized cataclastic shear, which is a candidate of small earthquake or very low frequency earthquake, is also recognized especially in sandstone blocks dominated portion in mélange. These observations are consistent with the mélange being a fault rock along the plate boundary that records various types of earthquakes in a subduction zone. The quantitative examination of the Mugi mélange suggests several criteria to define the tectonic mélange of the plate boundary fault in subduction zone from other mélanges in orogenic belt.

Kimura, Gaku; Yamaguchi, Asuka; Hojo, Megumi; Kitamura, Yujin; Kameda, Jun; Ujiie, Kohtaro; Hamada, Yohei; Hamahashi, Mari; Hina, Shoko

2012-09-01

40

Convergent plate margin dynamics: New perspectives from structural geology, geophysics and geodynamic modelling  

E-print Network

: Convergent plate margin Subduction Collision Orogenesis Slab Plate tectonics Convergent plate margins occur when two adjoining tectonic plates come together to form either a subduction zone, where at least one and discussions since the advent of plate tectonic theory. This paper provides a historical background

Rawlinson, Nick

41

Viscoelastic deformation near active plate boundaries  

NASA Technical Reports Server (NTRS)

Model deformations near the active plate boundaries of Western North America using space-based geodetic measurements as constraints are discussed. The first six months of this project were spent gaining familarity with space-based measurements, accessing the Crustal Dynamics Data Information Computer, and building time independent deformation models. The initial goal was to see how well the simplest elastic models can reproduce very long base interferometry (VLBI) baseline data. From the Crustal Dynamics Data Information Service, a total of 18 VLBI baselines are available which have been surveyed on four or more occasions. These data were fed into weighted and unweighted inversions to obtain baseline closure rates. Four of the better quality lines are illustrated. The deformation model assumes that the observed baseline rates result from a combination of rigid plate tectonic motions plus a component resulting from elastic strain build up due to a failure of the plate boundary to slip at the full plate tectonic rate. The elastic deformation resulting from the locked plate boundary is meant to portray interseismic strain accumulation. During and shortly after a large interplate earthquake, these strains are largely released, and points near the fault which were previously retarded suddenly catch up to the positions predicted by rigid plate models. Researchers judge the quality of fit by the sum squares of weighted residuals, termed total variance. The observed baseline closures have a total variance of 99 (cm/y)squared. When the RM2 velocities are assumed to model the data, the total variance increases to 154 (cm/y)squared.

Ward, S. N.

1986-01-01

42

The strength of large-scale plate boundaries: Constraints from the dynamics of the Philippine Sea plate since ~5 Ma  

NASA Astrophysics Data System (ADS)

Friction controls most of the strength of tectonic plate boundaries, and thus the force mutually exchanged between plates. Estimates of the plate-boundary friction-coefficient are therefore of paramount importance to our understanding of the lithosphere torque balance. However, several lines of evidence indicate that the friction-coefficient of plate margins is significantly lower than is measured in laboratory experiments performed on fractured rocks. This poses a significant limit to extrapolation from the laboratory scale to the large-scale of Earth's lithosphere. The record of past and present-day plate motions represents an efficient probe into the torque balance of plate tectonics, because plate-motions readjust virtually instantaneously to temporal changes in driving and resisting forces. Here I derive inferences on the strength of large-scale plate boundaries by focusing on the convergence of the fast-moving Philippine Sea plate towards Eurasia, since subduction initiation ~5 Myr ago. Because at the present-day the Philippine slab reaches depths shallower than the 410-km transition zone in the upper mantle, its weight is unlikely to provide sufficient driving force to shear the trailing plate over the viscous mantle at the observed rates. Using global models of the coupled mantle/lithosphere system, I argue that frictional coupling with the Pacific and Eurasia plates is the main driver for the dynamics of the Philippine Sea plate. This allows me to infer that the friction-coefficient of large-scale plate boundaries is in range 0.01 to 0.07, and that the amount of sediments entering plate margins efficiently modulates the friction-coefficient, contributing significantly to its lateral variations. Importantly, I corroborate my conclusions by focusing on the present-day vertical deformation of the Philippine Sea/Eurasia margin, evident from observed trench-parallel gravity anomalies.

Iaffaldano, G.

2012-12-01

43

The strength of large-scale plate boundaries: Constraints from the dynamics of the Philippine Sea plate since ˜5 Ma  

NASA Astrophysics Data System (ADS)

Friction controls most of the strength of tectonic plate boundaries, and thus the force mutually exchanged between plates. Estimates of the plate-boundary friction-coefficient are therefore of paramount importance to our understanding of the lithosphere torque balance. However, several lines of evidence indicate that the friction-coefficient of plate margins is significantly lower than is measured in laboratory experiments on fractured rocks. This poses a significant limit to extrapolation from the laboratory scale to the large-scale of Earth's lithosphere. The record of past and present-day plate motions represents an efficient probe into the torque balance of plate tectonics, because plate-motions readjust virtually instantaneously to temporal changes in driving and resisting forces. Here I derive inferences on the strength of large-scale plate boundaries by focusing on the convergence of the fast-moving Philippine Sea plate towards Eurasia, since subduction initiation ˜5 Myr ago. Because at the present-day the Philippine slab reaches depths shallower than the 410-km transition zone in the upper mantle, its weight is unlikely to provide sufficient driving force to shear the trailing plate over the viscous mantle at the observed rates. Using global models of the coupled mantle/lithosphere system, I argue that frictional coupling with the Pacific and Eurasia plates is the main driver for the dynamics of the Philippine Sea plate. This allows me to infer that the friction-coefficient of large-scale plate boundaries is in range 0.01-0.07, and that the amount of sediments entering plate margins efficiently modulates the friction-coefficient, contributing significantly to its lateral variations. Importantly, I corroborate my conclusions by looking at the present-day vertical deformation of the Philippine Sea/Eurasia margin, evident from observed trench-parallel gravity anomalies.

Iaffaldano, Giampiero

2012-12-01

44

Fluctuating boundary layer on a heated horizontal plate  

Microsoft Academic Search

Summary The paper deals with the boundary layer flow and heat transfer on a horizontal plate whose temperature differs from that of ambient fluid. The basic flow is purely induced by buoyancy which is caused by the difference of temperature in the plate and the fluid. The oscillation in the plate temperature causes a time dependent boundary layer flow and

P. Singh; V. P. Sharma; U. N. Misra

1978-01-01

45

Earthquakes, Plate Boundaries, and Depth Indiana Standard Indicators  

E-print Network

Earthquakes, Plate Boundaries, and Depth Indiana Standard Indicators: ES.1.23 ­ Explain motions the movement of the plates that make up the crust of the earth and the resulting formation of earthquakes Voyager, Jr." to correlate and assess the location of earthquakes and plate boundaries, the age

Polly, David

46

Development of transtensional and transpressive plate boundaries due to noncircular (cycloid) relative plate motion  

SciTech Connect

The trace of a transform fault commonly is assumed to be circular and concentric with the finite relative motion of the plates adjacent to the fault. These assumptions have led to controversy as the transform fault label has been applied to the San Andreas fault in California because the San Andreas fault is neither circular nor concentric with the motion of the Pacific plate relative to the North American plate. The assumption of circular relative plate motion over a finite time interval is not generally valid. When finite relative plate motion is not circular, the length and orientation of a transform fault must change through time. The length and orientation of ridge-ridge transform faults in oceanic crust evolve through the migration, propagation, and abandonment of ridge segments. Transform faults that bound continental crust evolve differently than do transform faults along mid-ocean ridges because continental transform faults typically do not have ridges at both ends and because of the rheological differences between oceanic and continental crust. Along continent-continent transform faults in which the initial displacement is entirely strike slip, later displacements will be progressively more divergent or convergent (i.e., transtensive or transpressive). Transtension can result in the development of deep basins with high heat flow. Transpression can result in folding, reverse faulting, and decoupling of the crust from its lower crustal or mantle lithosphere in the region adjacent to the transform fault. Regardless of whether the transform boundary becomes transtensional or transpressional, the boundary evolves from a discrete transform fault to a broader, structurally complex accommodation zone (sensu lato).

Cronin, V.S. (Univ. of Wisconsin, Milwaukee (USA))

1990-05-01

47

A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored  

E-print Network

A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries November 2001; accepted 15 November 2001 Abstract We developed a plate tectonic model for the Paleozoic rates and major tectonic and magmatic events. Plates were constructed through time by adding

Cerveny, Vlastislav

48

Identifying Plate Tectonic Boundaries for a Virtual Ocean Basin  

NSDL National Science Digital Library

Students observe a virtual ocean basin and two adjacent continental margins. From the characteristics of the sea floor and adjacent land, students infer where plate boundaries might be present. They then predict where earthquakes and volcanoes might occur. Finally, they draw their inferred plate boundaries in cross section.

Reynolds, Stephen

49

A diffuse plate boundary model for Indian Ocean tectonics  

Microsoft Academic Search

It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with

D. A. Wiens; Charles DeMets; R. G. Gordon; Seth Stein; Don Argus; Joseph F. Engeln; Paul Lundgren; Dan Quible; Carol Stein; Stuart Weinstein; Dale F. Woods

1985-01-01

50

Dynamics of diffuse oceanic plate boundaries: insensitivity to rheology  

Microsoft Academic Search

Diffuse plate boundaries, which are zones of deformation hundreds to thousands of kilometres wide, occur in both continental and oceanic lithosphere. Here, we build on our prior work in which we described analytic approximations to simple dynamical models that assume that the vertically averaged viscous force resisting deformation in diffuse oceanic plate boundaries (DOPBs) is described by either a linear

Stephen Zatman; Richard G. Gordon; Kartik Mutnuri

2005-01-01

51

POINTWISE CONVERGENCE ON THE BOUNDARY IN THE DENJOY-WOLFF THEOREM  

E-print Network

POINTWISE CONVERGENCE ON THE BOUNDARY IN THE DENJOY-WOLFF THEOREM PIETRO POGGI-CORRADINI Abstract POGGI-CORRADINI It is natural to ask whether for almost every point W the sequence n() still converges

Poggi-Corradini, Pietro

52

Active Faulting in the Ninetyeast Ridge and Implications for Diffuse Plate Boundaries of the Indo-Australian Plate  

NASA Astrophysics Data System (ADS)

The Ninetyeast Ridge (NER) in the central Indian Ocean is within a zone of diffuse deformation where the Indo-Australian plate is fracturing into three smaller plates (India, Capricorn, Australia). Deformation style appears to change across the NER and parts of the ridge are seismically active, suggesting that it holds clues about the diffuse plate boundaries. Seismic profiles collected along the NER image faults that show different styles of deformation along the length of the ridge. The northern NER (0-5°N) displays transpression along nearly east-west faults, likely a result of compression between India and Australia that is oblique to the NER. The observed faults explain the poorly understood distribution of earthquakes that occurred in April 2012 south of Sumatra. In the central NER (5-8°S), intense deformation results from nearly north-south compression, either from convergence of India and Capricorn or India and Australia. In contrast, deformation is slight and extensional in nature in the southern NER (10-27°S), which has little seismic activity. This deformation is inconsistent with predicted relative motions along much of the southern NER, implying that it is not a part of a plate boundary. Instead, we suggest that motion between the Capricorn and Australian plates follows ancient fracture zones east of the NER. At all sites, faulting appears controlled by the reactivation of original crustal faults, either normal faults formed by seafloor spreading or fracture zones, implying that diffuse deformation is opportunistic and is focused along existing zones of weakness.

Sager, W. W.; Bull, J. M.; Krishna, K. S.

2012-12-01

53

Relationship between the present-day stress field and plate boundary forces in the Pacific Northwest  

USGS Publications Warehouse

The relationship between plate boundary forces and the observed stress field in the Pacific Northwest is established using numerical models of continental deformation. Because the orientation of the greatest horizontal principal stress throughout the Pacific Northwest differs considerably from the direction of convergence between the Juan de Fuca and North American plates, the relationship between the stress field and forces acting along the subduction zone has been unclear. To address this relationship, a two-dimensional finite element model developed by Bird [1989] is used that incorporates critical aspects of continental deformation such as a stratified rheology and interaction between thermal and mechanical components of deformation. Boundary conditions are specified in terms of either velocity or shear traction, depending on whether the computed shear stress at the plate boundary is less than or exceeds, respectively, a prescribed limit. Shear-stress limits on the subduction and transform plate boundaries are independently varied to determine the relative effect of forces along these boundaries on intraplate deformation. Results from this study indicate that the shear stress limit of both subduction and transform boundaries is low, and that the intraplate stress field is attributed, in part, to the normal component of relative plate motion along the transform boundaries. However, the models also indicate that although the subduction zone fault is weak, a minimum shear strength ( ??? 10 MPa) for the fault is necessary to explain the observed stress field. The balance among forces along the tectonic boundaries of North America results in a surprising degree of variation in the present-day stress field.

Geist, E. L.

1996-01-01

54

The Okhotsk Plate and the Eurasia-North America plate boundary zone.  

NASA Astrophysics Data System (ADS)

The Eurasia-North America plate boundary zone transitions from spreading at rates of ~ 25mm/yr in the North Atlantic, to compression at rates of ~ 5mm/yr in the region of the Okhotsk plate. Because the pole of rotation between Eurasia and North America lies more or less on their mutual boundary, there is a linear change in rate along the boundary, and regions near the euler pole are subject to extremely low deformation rates. The Okhotsk - Eurasia - North America triple junction lies slightly south of the rotation pole, placing the Okhotsk plate entirely in a weakly contractional setting. Regions near the triple junction absorb 1mm/yr contraction. Further south, towards the shoreline of the Okhotsk sea, up to 5 mm/yr contraction may be absorbed within the plate. How shortening is accommodated across the boundary remains an open question. One possibility is wholesale extrusion of the entire Okhotsk plate (or possibly its northwestern corner) along two plate boundary strike slip faults (Eurasia-Okhostk and North America Okhotsk). The problem with this model is that the seismic record does not presently clearly support it, with the largest events distributed both within the plate interior and on its boundaries. This may suggest that instead, the Okhotsk plate, and particularly its north-western end, consists of a series of smaller blocks which shuffle against each other, partially accommodating extrusion, but also permitting some internal deformation and change of shape of the Okhotsk plate itself. We present analyses of the very sparse seismic record from the region, as well as geometric-kinematic, tectonic models of the possible deformation of northwest Okhotsk to try to better understand the different probabilities of how this slowly deforming plate boundary zone is behaving.

Hindle, David; Mackey, Kevin

2014-05-01

55

Melt generation in the Earth's mantle at Convergent Plate Margins  

E-print Network

The five geologic studies presented in this thesis document how the recycling of tectonic plates at subduction zones has a profound effect on the melting behavior of the Earth's mantle. Two experimental studies (Chapters ...

Till, Christy B

2011-01-01

56

The accommodation of Arabia-Eurasia plate convergence in Iran  

Microsoft Academic Search

Continental convergence between Arabia and Eurasia is taken up by distributed deformation in Iran. At wavelengths large compared with the thickness of the lithosphere this deformation is best described by a continuous velocity field. The only quantitative source of information on the spatial distribution of strain rates within Iran is the record of earthquakes. We find that we can reproduce

James Jackson; John Haines; William Holt

1995-01-01

57

Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone  

Microsoft Academic Search

THE Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3) to 9

Alan R. Nelson; Brian F. Atwater; Peter T. Bobrowsky; Lee-Ann Bradley; John J. Clague; Gary A. Carver; Mark E. Darienzo; Wendy C. Grant; Harold W. Krueger; Rodger Sparks; Thomas W. Stafford; Minze Stuiver

1995-01-01

58

Plate convergence, transcurrent faults and internal deformation adjacent to Southeast Asia and the western Pacific  

NASA Technical Reports Server (NTRS)

A model for oblique convergence between plates of lithosphere is proposed in which at least a fraction of slip parallel to the plate margin results in transcurrent movements on a nearly vertical fault which is located on the continental side of a zone of plate consumption. In an extreme case of complete decoupling only the component of slip normal to the plate margin can be inferred from underthrusting. Recent movements in the western Sunda region provide the most convincing evidence for decoupling of slip, which in this region is thought to be oblique to the plate margin. A speculative model for convergence along the margins of the Philippine Sea is constructed from an inferred direction of oblique slip in the Philippine region. This model requires that the triple point formed by the junction of the Japanese and Izu-Bonin trenches and the Nankai trough migrate along the Sagami trough.

Fitch, T. J.

1971-01-01

59

A diffuse plate boundary model for Indian Ocean tectonics  

NASA Technical Reports Server (NTRS)

It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.

Wiens, D. A.; Demets, C.; Gordon, R. G.; Stein, S.; Argus, D.

1985-01-01

60

Iberian plate kinematics: A jumping plate boundary between Eurasia and Africa  

USGS Publications Warehouse

THE rotation of Iberia and its relation to the formation of the Pyrenees has been difficult to decipher because of the lack of detailed sea-floor spreading data, although several models have been proposed1-7. Here we use detailed aeromagnetic measurements from the sea floor offshore of the Grand Banks of Newfoundland to show that Iberia moved as part of the African plate from late Cretaceous to mid-Eocene time, with a plate boundary extending westward from the Bay of Biscay. When motion along this boundary ceased, a boundary linking extension in the King's Trough to compression along the Pyrenees came into existence. Finally, since the late Oligocene, Iberia has been part of the Eurasian plate, with the boundary between Eurasia and Africa situated along the Azores-Gibraltar fracture zone.

Srivastava, S.P.; Schouten, Hans; Roest, W.R.; Klitgord, Kim D.; Kovacs, L.C.; Verhoef, J.; Macnab, R.

1990-01-01

61

Preliminary estimates of plate convergence in the Caucasus collision zone from global positioning system measurements  

Microsoft Academic Search

Global Positioning System (GPS) measurements (1991-1994) traversing the Greater and Lesser Caucasus mountains indicate a minimum N-S shortening of 10+\\/-2mm\\/yr. This represents approximately 30-50% of the NUVEL-1A convergence rate between the Arabian and Eurasian plates. The remainder of the convergence appears to be accommodated in the areas south of the Lesser Caucasus, by a combination of right-lateral strike-slip faulting on

R. E. Reilinger; S. C. McClusky; B. J. Souter; M. W. Hamburger; M. T. Prilepin; A. Mishin; T. Guseva; S. Balassanian

1997-01-01

62

Fluid budgets at convergent plate margins: Implications for the extent and duration of fault-zone dilation  

USGS Publications Warehouse

Faults at convergent plate boundaries are important conduits for fluid escape, and recent evidence suggests that fluid expulsion along them is both transient and heterogeneous. For the Nankai and Barbados convergent margins, we have used numerical models to investigate the long-term partitioning of expelled fluids between diffuse flow and flow along connected high-permeability fault conduits. For a simple case of spatial heterogeneity, we estimated the extent of high-permeability conduits necessary to maintain a balance between incoming and expelled fluids. For the case of transient expulsion, we constrained the duration of elevated permeability required to balance the fluid budgets. Comparison of modeled and observed geochemical profiles suggests that the initiation of connected flow conduits is delayed with respect to the time of accretion into each accretionary complex and may be related to burial below a critical depth, either where the overlying wedge is sufficiently thick to prevent fluid escape to the sea floor or where sediments behave brittlely.

Saffer, D. M.; Bekins, B. A.

1999-01-01

63

Organized melt, seismic anisotropy, and plate boundary lubrication  

NASA Astrophysics Data System (ADS)

Based on observations in both the laboratory and the Earth, we develop the hypothesis that plate boundaries are lubricated by networks of melt-rich shear zones. Such lubrication would serve to reduce effective strength and focus deformation at plates boundaries. This idea emerges from two sets of observations: (1) stress-driven melt segregation and organization in experimentally deformed mantle rocks and (2) seismic anisotropy patterns as observed at three divergent plate boundaries (the Ethiopian Rift, the Reykjanes Ridge, and the East Pacific Rise). In all three tectonic settings, the magnitude of anisotropy is greatest at the probable locations of the lithosphere-asthenosphere boundary within the plate boundary ("marginal LAB"). Seismic anisotropy in the upper mantle is controlled by the lattice preferred orientation (LPO) of predominant olivine and the alignment of melt structures. The observed patterns of anisotropy are controlled by the dip angle of the marginal LAB. When steeply dipping, shear wave splitting in vertically traveling waves (e.g., SKS phases) is most sensitive to the alignment of melt, and surface waves should reveal faster Rayleigh wave velocities than Love wave velocities (VSV > VSH). When shallowly dipping, shear wave splitting in vertically traveling body waves is controlled by olivine LPO, and surface waves show faster Love wave velocities than Rayleigh wave velocities (VSV < VSH). The formation of melt-rich networks by stress-driven segregation should be most effective where strain rates are highest. These melt-lubricated shear zones will reduce effective viscosity relative to the direct extrapolation of viscosity values derived from laboratory creep experiments on homogenous samples. A composite model of anisotropic seismic properties is developed to test the hypothesis that melt segregates along the LAB, incorporating olivine fabrics with oriented and segregated melt over a range of length scales. This model is applied to observations from the three example plate boundaries, leaving the reader to speculate on the implications for interpretation of anisotropy patterns at other geodynamic settings.

Holtzman, Benjamin K.; Kendall, J.-Michael

2010-12-01

64

Cocos Ridge Collision as a Driver for Plate Boundary Deformation in the Western Caribbean  

NASA Astrophysics Data System (ADS)

The subduction and collision of bathymetric highs can result in geodynamic changes along convergent plate boundaries, including intense upper plate deformation, increases in mechanical coupling and seismicity, migration and or cessation of volcanism and formation of forearc terranes. But how extensive can the deformation associated with these features be and what are the implications for the long-term formation and evolution of plate boundary zones? Plate boundary evolution and upper plate deformation in southern Central America associated with Cocos Ridge collision is well studied and indicates, 1) migration of the volcanic arc toward the backarc northwest of and cessation of volcanism directly inboard the ridge, 2) uplift of the Cordillera de Talamanca inboard the ridge, 3) shortening across the forearc Fila Costena fold and thrust belt, and 4) outer forearc uplift above and flanking the ridge. Recent geodynamical modeling of Cocos Ridge collision, combined with the results of kinematic block models for the Central American margin, suggests the ridge drives northwest-directed forearc motion from central Costa Rica northwest to the Cocos - Caribbean (Central American forearc block) - North America triple junction, greatly increasing the spatial scale of deformation. Upperplate deformation of the Central American margin to the southeast of the Cocos Ridge in Panama was not investigated in these models. We investigate the dynamics of Cocos Ridge collision along the entire Central American margin and the implications on plate boundary evolution with a new geodynamic model of ridge collision. Our model results are compared to a new GPS derived horizontal velocity field for Central America and preliminary results indicate that the Cocos Ridge drives the Panamanian isthmus into northern South America (i.e., the North Andes block).

La Femina, P. C.; Govers, R. M.; Geirsson, H.; Kobayashi, D.

2011-12-01

65

Nonlinear plate aeroelastic response with uncertain stiffness and boundary conditions  

Microsoft Academic Search

The probabilistic response of a nonlinear panel in supersonic flow is investigated using a new computational methodology. The aeroelastic system is modelled by coupling the von Karman plate equations with piston theory aerodynamics. Baseline deterministic results are compared to published data to establish validity of the aeroelastic model. Uncertainties in modulus of elasticity and boundary conditions (BCs) are considered, with

Ned J. Lindsley; Chris L. Pettit; Philip S. Beran

2006-01-01

66

The Earthscope Plate Boundary Observatory Akutan Alaskan Volcano Network Installation  

Microsoft Academic Search

During June and July of 2005, the Plate Boundary Observatory (PBO) installed eight permanent GPS stations on Akutan Volcano, in the central Aleutian Islands of Alaska. PBO worked closely with the Alaska Volcano Observatory and the Magmatic Systems Site Selection working group to install stations with a spatial distribution to monitor and detect both short and long term volcanic deformation

B. Pauk; M. Jackson; D. Mencin; J. Power; W. Gallaher; A. Basset; K. Kore; Z. Hargraves; T. Peterson

2005-01-01

67

In-Plane Vibration Analysis of Annular Plates with Arbitrary Boundary Conditions  

PubMed Central

In comparison with the out-of-plane vibrations of annular plates, far less attention has been paid to the in-plane vibrations which may also play a vital important role in affecting the sound radiation from and power flows in a built-up structure. In this investigation, a generalized Fourier series method is proposed for the in-plane vibration analysis of annular plates with arbitrary boundary conditions along each of its edges. Regardless of the boundary conditions, the in-plane displacement fields are invariantly expressed as a new form of trigonometric series expansions with a drastically improved convergence as compared with the conventional Fourier series. All the unknown expansion coefficients are treated as the generalized coordinates and determined using the Rayleigh-Ritz technique. Unlike most of the existing studies, the presented method can be readily and universally applied to a wide spectrum of in-plane vibration problems involving different boundary conditions, varying material, and geometric properties with no need of modifying the basic functions or adapting solution procedures. Several numerical examples are presented to demonstrate the effectiveness and reliability of the current solution for predicting the in-plane vibration characteristics of annular plates subjected to different boundary conditions. PMID:24688416

Qin, Zhengrong; Wang, Qingshan

2014-01-01

68

On the Relationship between SST Gradients, Boundary Layer Winds, and Convergence over the Tropical Oceans  

E-print Network

A linear mixed layer model that skillfully reproduces observed surface winds and convergence over the tropical oceans is used to examine the relative influence of boundary layer and free-tropospheric processes on the ...

Bretherton, Christopher S.

69

The boundary layer on a finite flat plate  

NASA Astrophysics Data System (ADS)

The problem of finding the flow over a finite flat plate aligned with a uniform free stream is revisited. Multigrid is used to obtain accurate numerical solutions up to a Reynolds number of 4000. Fourier boundary conditions keep the computational domain small, with no loss of accuracy. Near the trailing edge, excellent agreement with first-order triple-deck theory is found. However, previous comparisons between computations, experiments, and triple-deck theory are shown to be misleading: In fact, triple-deck theory only accounts for half the drag excess (that part not due to the first-order Blasius boundary layer) even at R=4000. The remainder is shown to be due to, among other things, a large displacementlike effect in the boundary layer, i.e., an O(R-1) increase in skin friction extending over the whole plate.

McLachlan, Robert I.

1991-02-01

70

The convergence-fault mechanism for low-angle boundary formation in single-crystal castings  

Microsoft Academic Search

A set of nickel-based superalloy single-crystal investment castings was evaluated for crystal perfection. Defect structures near the seed emergence point and other geometric features were examined using X-ray topography. Topographic images were compared with metallographically observed dendritic structures to establish a convergence-fault criterion for the location of low-angle boundaries. To support the phenomenological description of low-angle boundary formation through convergence-faulting,

R. E. Napolitano; R. J. Schaefer

2000-01-01

71

Overriding plate structure of the Nicaragua convergent margin: Relationship to the seismogenic zone of the 1992 tsunami earthquake  

NASA Astrophysics Data System (ADS)

We present 2-D seismic velocity models and coincident multichannel seismic reflection images of the overriding plate and the inter-plate boundary of the Nicaragua convergent margin along two wide-angle seismic profiles parallel and normal to the trench acquired in the rupture area of the 1992 tsunami earthquake. The trench-perpendicular profile runs over a seamount subducting under the margin slope, at the location where seismological observations predict large coseismic slip. Along this profile, the igneous basement shows increasing velocity both with depth and away from the trench, reflecting a progressive decrease in upper-plate rock degree of fracturing. Upper mantle-like velocities are obtained at ˜10 km depth beneath the fore-arc Sandino basin, indicating a shallow mantle wedge. A mismatch of the inter-plate reflector in the velocity models and along coincident multichannel seismic profiles under the slope is best explained by ˜15% velocity anisotropy, probably caused by subvertical open fractures that may be related to fluid paths feeding known seafloor seepage sites. The presence of a shallow, partially serpentinized mantle wedge, and the fracture-related anisotropy are supported by gravity analysis of velocity-derived density models. The downdip limit of inter-plate seismicity occurs near the tip of the inferred mantle wedge, suggesting that seismicity could be controlled by the presence of serpentinite group minerals at the fault gouge. Near the trench, the inferred local increase of normal stress produced by the subducting seamount in the plate boundary may have made this fault segment unstable during earthquake rupture, which could explain its tsunamigenic character.

Sallarès, Valentí; Meléndez, Adrià; Prada, Manuel; Ranero, César R.; McIntosh, Kirk; Grevemeyer, Ingo

2013-09-01

72

Late Cenozoic partitioning of oblique plate convergence in the Zagros fold-and-thrust belt (Iran)  

E-print Network

Late Cenozoic partitioning of oblique plate convergence in the Zagros fold-and-thrust belt (Iran. Chardon, O. Bellier, Z. Malekzadeh, E. Shabanian, and M. R. Abbassi (2006), Late Cenozoic partitioning Cenozoic space and time relationships between the creation of the fold-and- thrust belt and the activity

Paris-Sud XI, Université de

73

Global positioning system measurements of Indian plate motion and convergence across the Lesser Himalaya  

Microsoft Academic Search

We use Global Positioning System (GPS) measurements acquired from 1991 to 1995 to constrain the motion of sites in Bangalore, in southern India, and Kathmandu, Nepal, relative to a global GPS network. These measurements permit estimates of the northward motion of the Indian plate and convergence between the southern Himalaya and the Indian subcontinent. The velocities of Bangalore and Kathmandu

J. Freymueller; R. Bilham; R. Bürgmann; K. M. Larson; J. Paul; S. Jade; V. Gaur

1996-01-01

74

Integrating Seismological and Tectonic Studies to Constrain Lithospheric Evolution at Complex Plate Boundaries.  

E-print Network

??The relative motion of tectonic plates across their boundaries generates deformation in the surrounding lithosphere. How this deformation is expressed reflects both present-day plate configurations… (more)

Hayes, Gavin

2007-01-01

75

Geological record of fluid flow and seismogenesis along an erosive subducting plate boundary.  

PubMed

Tectonic erosion of the overriding plate by the downgoing slab is believed to occur at half the Earth's subduction zones. In situ investigation of the geological processes at active erosive margins is extremely difficult owing to the deep marine environment and the net loss of forearc crust to deeper levels in the subduction zone. Until now, a fossil erosive subduction channel-the shear zone marking the plate boundary-has not been recognized in the field, so that seismic observations have provided the only information on plate boundary processes at erosive margins. Here we show that a fossil erosive margin is preserved in the Northern Apennines of Italy. It formed during the Tertiary transition from oceanic subduction to continental collision, and was preserved by the late deactivation and fossilization of the plate boundary. The outcropping erosive subduction channel is approximately 500 m thick. It is representative of the first 5 km of depth, with its deeper portions reaching approximately 150 degrees C. The fossil zone records several surprises. Two décollements were simultaneously active at the top and base of the subduction channel. Both deeper basal erosion and near-surface frontal erosion occurred. At shallow depths extension was a key deformation component within this erosive convergent plate boundary, and slip occurred without an observable fluid pressure cycle. At depths greater than about 3 km a fluid cycle is clearly shown by the development of veins and the alternation of fast (co-seismic) and slow (inter-seismic) slip. In the deepest portions of the outcropping subduction channel, extension is finally overprinted by compressional structures. In modern subduction zones the onset of seismic activity is believed to occur at approximately 150 degrees C, but in the fossil channel the onset occurred at cooler palaeo-temperatures. PMID:18256668

Vannucchi, Paola; Remitti, Francesca; Bettelli, Giuseppe

2008-02-01

76

Discovering plate boundaries: Laboratory and classroom exercises using geodetic data to develop students' understanding of plate motion  

Microsoft Academic Search

To introduce the concept of plate boundaries, typical introductory geology exercises include students observing and plotting the location of earthquakes and volcanoes on a map to visually demarcate plate boundaries. Accompanying these exercises, students are often exposed to animations depicting the movement of Earth's tectonic plates over time. Both of these teaching techniques are very useful for describing where the

S. E. Olds

2010-01-01

77

Dynamic Plate Boundaries and Restored Synthetic Isochrons: The Indispensable Tools To Constrain Plate Tectonic Models  

NASA Astrophysics Data System (ADS)

We developed a plate tectonics model for the Paleozoic and Mesozoic (Ordovician to Cretaceous) integrating dynamic plate boundaries, plate buoyancy, ocean-spreading rates and major tectonic and magmatic events. Plates have been constructed through time by adding/removing oceanic material symbolized by syntethic isochrones, to ma- jor continents and terranes. These oceanic isochrons have been constructed through time in order to define the location of the spreading ridges and to restore subducted ocean basins. To simplify the process we worked with a symmetrical sea floor spread- ing for the main oceans (Paleo- and NeoTethys). Driving forces like slab pull and slab buoyancy were used to constrain the evolution of paleo-oceanic domains. This ap- proach offers a good control on the sea floor spreading and plate kinematics. This new method represents a distinct departure from classical continental drift reconstructions, which are not constrained due to the lack of plate boundaries. This model allows a more comprehensive analysis of the development of the Tethyan realm in space and time. In particular, the relationship between the Variscan and the Cimmerian cycles in the Mediterranean-Alpine realm is clearly illustrated by numerous maps. For the Alpine cycle, the relationship between the Alpides senso stricto and the Tethysides is also explicable in terms of plate tectonic development of the Alpine Tethys-Atlantic domain versus the NeoTethys domain.

Borel, G. D.; Stampfli, G. M.

78

TTR triple junction evolution during plate convergence in the southern branch of the european variscan orogen  

NASA Astrophysics Data System (ADS)

The boundary between the Ossa-Morena and the South Portuguese zones (Iberian Massif) represents a major suture within the southern branch of the European Varis-can orogen. This suture resulted from the collision between the northern Iberian autochthon and the South Portuguese allochthon, and it is outlined by a WNW-ESE oriented, high grade band (the Aracena metamorphic belt, AMB). The main characteristics of the AMB are (1) the presence of a linear belt of MORB derived metabasites which shows a HT/LP inverted metamorphic gradient (Castro et al., 1996). This metamorphic event shows an age gradient (Castro et al., 1999), in such a way that younger ages have been obtained towards the east. (2) The occur-rence of a UHT/LP metamorphic event, related to an extensional deformation phase, affecting the former continental margin of the Iberian autochthon. (3) The existence of syn-to-post-tectonic noritic intrusions with boninite affinity composition, related to partial melting of a shallow mantle wedge (Castro et al., 1996). According to the mentioned characteristics the following tectonic model is pro-posed: (1) During the convergence between the Iberian autochthon and the South Portuguese allochthon, an oceanic ridge intersected the subduction zone giving place to a TTR triple junction, related to which a slab-free window formed and a thermal rebound took place. This triple junction migrated along the continental edge of the Iberian autochthon towards the east, generating a high-grade metamorphic belt (the AMB). (3) As the trailing oceanic plate subducted beneath the continental margin, it was heated up by the latter. In consequence, the upper levels of the oceanic sheet became dehydrated and were accreted to the base of the continental margin. The subduction plane migrated downwards and the oceanic metabasites together with the continental margin overthrusted the rest of the oceanic plate and the accretionary prism. (4) Once the trailing oceanic plate was totally consumed, a continental colli-sion occurred between the South Portuguese allochthon and the Iberian autochthon. Castro, A., Fernández, C., de la Rosa, J.D., Moreno-Ventas, I., Rogers, G. (1996) Journal of Petrology, 37, 235-260. Castro, A., Fernández, C., El-Hmidi, H., El-Biad, M., Díaz, M., de la Rosa, J.D., Stuart, F. (1999) International Journal of Earth Sciences, 88, 26-37.

Diaz, M.; Fernandez, C.; Castro, A.

2003-04-01

79

A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons  

Microsoft Academic Search

We developed a plate tectonic model for the Paleozoic and Mesozoic (Ordovician to Cretaceous) integrating dynamic plate boundaries, plate buoyancy, ocean spreading rates and major tectonic and magmatic events. Plates were constructed through time by adding\\/removing oceanic material, symbolized by synthetic isochrons, to major continents and terranes. Driving forces like slab pull and slab buoyancy were used to constrain the

G. M Stampfli; G. D. Borel

2002-01-01

80

Tectonics of the Nazca-Antarctic plate boundary  

NASA Technical Reports Server (NTRS)

A new bathymetric chart of part of the Chile transform system is constructed, based mainly on an R/V Endeavor survey from 100 deg W to its intersection with the East Ridge of the Juan Fernandez microplate. A generally continuous lineated trend can be followed through the entire region, with the transform valley being relatively narrow and well-defined from 109 deg W to approximately 104 deg 30 min W. The fracture zone then widens to the east, with at least two probable en echelon offsets to the south at 104 deg and 102 deg W. Six new strike-slip mechanisms along the Chile Transform and one normal fault mechanism near the northern end of the Chile Rise, inverted together with other plate-motion data from the eastern portion of the boundary, produce a new best-fit Euler pole for the Nazca-Antarctic plate pair, providing tighter constraints on the relative plate motions.

Anderson-Fontana, Sandra; Larson, Roger L.; Engeln, Joseph F.; Lundgren, Paul; Stein, Seth

1987-01-01

81

Imprints of weak lithospheric plate boundaries in the observed geoid.  

NASA Astrophysics Data System (ADS)

The observed geoid is highly sensitive to both: density-viscosity variations within the Earth and lithosphere dynamics. While geoid undulations induced by the mantle dynamics is a subject of numerous studies, the effect of plate tectonics on the geoid and dynamic topography remains an open issue. In present study we investigate a joint effect of weak zones, dividing lithospheric plates, and lateral viscosity variations (LVV) in the whole mantle on the observed geoid. A new numerical technique is based on the substantially revised method introduced by Zhang and Christensen (1993) for solving the Navier-Stokes-Poisson equations in the spectral domain with strong LVV. Weak plate boundaries (WPB) are introduced based on the integrated global model of plate boundary deformations GSRM (Kreemer et al., 2003). We show that the effect of WPB on the geoid is significant and reaches -40 m to 70 m with RMS ~20 m. Maximal WPB-related anomalies are observed over large subduction zones in South America and the Southwestern Pacific in agreement with previous studies. The positive geoid anomaly in South America could be explained largely by a dynamic effect of decoupling of the Nazca and South American plates. Mid-ocean ridges are mostly characterized by negative changes of the geoid compared to the model without WPB. The amplitude of the effect depends on the viscosity contrasts across WPB until its value reaches the limit of 2.5-3 orders of magnitude. This value might be considered as the level at which plates are completely decoupled. The effect of WPB alone, exceeds the effect of LVV in the whole mantle and generally does not correlate with it. However, inclusion of LVV reduces the geoid perturbations due to WPB by about 10 m. Therefore, it is important to consider all these factors together. The geoid changes mainly result from changes of the dynamic topography, which are about -300 to +500 m. The obtained results show that including WPB may significantly improve the reliability of instantaneous global dynamic models. References Zhang, S., and U. Christensen (1993), Some effects of lateral viscosity variations on geoid and surface velocities induced by density anomalies in the mantle, Geophys. J. Int., 114(3), 531-547 Kreemer, C., W. E. Holt, and A. J. Haines (2003), An integrated global model of present-day plate motions and plate boundary deformation, Geophys. J. Int., 154(1), 8-34

Petrunin, Alexey G.; Kaban, Mikhail K.; Schmeling, Harro; Shahraki, Meysam

2014-05-01

82

Your Mission: To become familiar with the major plate boundaries through exploration of plate tectonic features using Google Earth.  

E-print Network

boundaries through exploration of plate tectonic features using Google Earth. Your Supplies: (1) A computer with internet access and the Google Earth program of Earth's tectonic plates using Google Earth. To do this, login

Smith-Konter, Bridget

83

Buckling transition and boundary layer in non-Euclidean plates  

E-print Network

Non-Euclidean plates are thin elastic bodies having no stress-free configuration, hence exhibiting residual stresses in the absence of external constraints. These bodies are endowed with a three-dimensional reference metric, which may not necessarily be immersible in physical space. Here, based on a recently developed theory for such bodies, we characterize the transition from flat to buckled equilibrium configurations at a critical value of the plate thickness. Depending of the reference metric, the buckling transition may be either continuous or discontinuous. In the infinitely thin plate limit, under the assumption that a limiting configuration exists, we show that the limit is a configuration that minimizes the bending content, amongst all configurations with zero stretching content (isometric immersions of the mid-surface). For small but finite plate thickness we show the formation of a boundary layer, whose size scales with the square root of the plate thickness, and whose shape is determined by a balance between stretching and bending energies.

Efi Efrati; Eran Sharon; Raz Kupferman

2009-02-17

84

Kinematics of subduction and plate convergence under Taiwan and its geomorphic, geodetic and seismic expressions  

NASA Astrophysics Data System (ADS)

Deciphering the kinematics of ongoing subduction and rapid plate convergence under Taiwan is neither trivial nor straightforward. A 3D synthesis of diverse constraints is required, for example tomography, geodesy, tectonic geomorphology, stress inversion, and Philippine Sea plate motions. Eurasian-Philippine Sea plate convergence is ~90mm/y in a mildly oblique 300° azimuth relative to the ~NS nearly vertically subducting Eurasian mantle lithosphere which extends to ~500km depth. If all the current plate convergence were consumed in subduction of Eurasian mantle, the subduction flexural hinge would migrate westward at ~80mm/y, which is fast relative to the ~30mm/y long-term slip rate on the Taiwan main detachment that represents the Eurasian subduction interface under the Taiwan Central Mountains. If this fast simple subduction were occurring, subduction would too quickly outrun the mountain belt in conflict with data. Instead we estimate that subduction of Eurasian lithosphere is proceeding at ~50mm/y with the remaining ~40mm/y convergence at a lithospheric level consumed by secondary subduction above and to the east of the main plate interface. This secondary subduction is largely transient deformation that is most obvious under the Coastal Range, which represents the deforming western margin of the Philippine Sea plate during the last ~1-1.5 Ma. The thrust faults of the Coastal Range function as subduction faults with the long-term net motion of their footwalls moving largely down relative to their only slowly uplifting hanging walls, with a net secondary subduction of ~40-50km in the last ~1-1.5Ma as estimated from seismic tomography and other data. In addition we find evidence for ongoing subduction of the eastern Central Mountains of Taiwan. The crest of the mountains coincides with the western edge of the migrating plate flexure, a band of extensional geodetic strain coincides with the flexure, and an extensional stress state in the upper 5-10km coincides with the zone of flexure. Kinematic modeling of leveling and gps data is consistent with a migration rate of the hinge of ~50mm/y, which would be the subduction rate of Eurasian mantle lithosphere. This rate is somewhat faster than the long-term rate of ~30mm/y since ~15Ma, but less than the current slab-normal plate rate of ~80mm/y, which is thought to represent a speed-up in the last ~1-2Ma. This kinematic modeling also suggests that the main subduction interface under the eastern Central Mountains could be widely locked; if so it has substantial seismic potential at its ~12-13km depth.

Suppe, J.; Carena, S.; Kanda, R. V.; Wu, Y.; Huang, H.; Wu, J. E.

2013-12-01

85

Strain partitioning during oblique plate convergence in northern Sumatra: Geodetic and seismologic constraints and numerical modeling  

Microsoft Academic Search

Global Positioning System (GPS) measurements along the subduction zone of northern Sumatra (2°S to 3°N) reveal that the strain associated with the oblique convergence of the Australian plate with Eurasia is almost fully partitioned between trench-normal contraction within the forearc and trench-parallel shear strain within a few tens of kilometers of the Sumatran fault. Kinematic analyses of interplate earthquake slip

Robert McCaffrey; Peter C. Zwick; Yehuda Bock; Linette Prawirodirdjo; Joachim F. Genrich; Colleen W. Stevens; S. S. O. Puntodewo; Cecep Subarya

2000-01-01

86

Sub-slab mantle flow parallel to the Caribbean plate boundaries: Inferences from SKS splitting  

NASA Astrophysics Data System (ADS)

Upper-mantle deformation near the margins of the Caribbean plate is investigated using observations of shear-wave splitting in teleseismic and local shear phases. The Caribbean plate is almost stationary in the hot-spot reference frame and is wedged between the North America, South America, Nazca and Cocos plates; collisional belts and major shear zones encircle the plate. Data from seismic stations operated by IRIS, GEOSCOPE, the Venezuelan Seismological Network, and the British Geological Survey have provided nearly 2000 seismic records for analysis. Analysis of shear-wave splitting in teleseismic core phases (e.g., SKS) at stations reveals fast shear-wave polarisations that are conformal to the plate boundary, paralleling the major structural features. The magnitude of the splitting is in general quite large (1.2-2.1 s). In northern Venezuela, the magnitude of splitting increases towards the Caribbean-South American collisional front. Local shear phases from earthquakes up to 200 km deep beneath northeastern Venezuela show very small amounts of splitting (0.1-0.3 s). Analysis of the depth dependence in the magnitude of the splitting suggests that most of the upper-mantle wedge is isotropic and the splitting in the local phases is mostly accrued in the crust and uppermost mantle. In NE Venezuela fast shear-wave polarisations in both the local and teleseismic phases closely parallel the fault systems in the region, suggesting that the crust and mantle are coupled in this area. Stations on the Island of Montserrat and near Bucaramanga, Columbia, also show very small magnitudes in local S-wave splitting, but large amounts of SKS splitting. In general, the small magnitude of the local S-phase splitting suggests that the teleseismic phases accrue considerable splitting beneath the top of the slab. We interpret the bulk of the splitting in terms of sub-slab flow that is forced around the Caribbean plate due to the convergence of the surrounding plates.

Piñero-Feliciangeli, L. T.; Kendall, J.-M.

2008-12-01

87

Turbulent thermal boundary layer on a permeable flat plate  

SciTech Connect

Scaling laws are established for the profiles of temperature, turbulent heat flux, rms temperature fluctuation, and wall heat transfer in the turbulent boundary layer on a flat plate with transpiration. In the case of blowing, the temperature distribution represented in scaling variables outside the viscous sublayer has a universal form known from experimental data for flows over impermeable flat plates. In the case of suction, the temperature distribution is described by a one-parameter family of curves. A universal law of heat transfer having the form of a generalized Reynolds analogy provides a basis for representation of the heat flux distributions corresponding to different Reynolds numbers and transpiration velocities in terms of a function of one variable. The results are obtained without invoking any special closure hypotheses.

Vigdorovich, I. I. [Moscow State University, Institute of Mechanics (Russian Federation)], E-mail: vigdorovich@imec.msu.ru

2007-06-15

88

Neotectonic and structural characteristics along the Chaochou fault system in SW Taiwan: implications for tectonic escape during oblique plate convergence  

NASA Astrophysics Data System (ADS)

Tectonic escape has been recognized as a common geologic process that relates to the lateral expulsion of a tectonic block during oblique plate convergence and collision. To better understand fault behaviors in such tectonically active regions, we characterized short-term and recent deformation in the SW Taiwan, where deformation largely associates with tectonic escape. This study focuses on a prominent boundary for the tectonic escape: the Chaochou fault system, which separates the Eo-Miocene slate belt of the Central Range and an extensive composite of alluvium plains. Structural data show that the Chaochou fault cut across the strike of the slaty cleavage within the Central Range, suggesting that the fault developed at later stages during the Pio-Pleistocene plate convergence. Morphologic features along the Chaochou fault suggest presence of several active fault strands and changeable mountain front characteristics. The northern and middle portions of the fault show evidence of compression and uplifting based on alluvial fans and river terraces. In contrast, the southern portion of the fault shows significant embayments at river mouths, which may suggest slower rate of uplifting or even subsidence in the southern segment. GPS data from this area indicate extensional deformation with some left lateral movement component in the southern portion. Data from seismicity indicate complex deformation at present along the length of the fault. Locations of three swarms of seismicity suggest current fault activities are underneath the Central Range. Unexpectedly, just below the Chaochou fault shows little seismicity, suggesting the fault may be locked and the deformation is largely taking place in the Central Range at the moment. These observations indicate diverse patterns of deformation along the Chaochou fault, the eastern boundary fault for the tectonic escape in the SW Taiwan. The patterns of deformation imply that the process of tectonic escape may involve compression and relaxation through various faulting mechanisms during the process. In addition, extension may be common at the outer portion of the escaped block where widened space contributes to such tectonic adjustment.

Chan, Y.; Lee, J.; Lu, C.; Hu, J.; Chu, H.; Hou, C.; Rau, R.; Ching, K.

2002-12-01

89

An Introduction to Plate Tectonics  

NSDL National Science Digital Library

This page is a brief introduction to plate tectonics. It starts with a discussion of the evolution of the theory of plate tectonics and the arguments supporting it. It then discusses the processes associated with tectonics and the types of plate boundaries: divergent, convergent and transform boundaries. It concludes with a discussion of the current hypotheses of what causes plates to move.

90

Crustal movement along a collision boundary of plates (case of eastern Taiwan)  

NASA Astrophysics Data System (ADS)

Recent crustal movements in eastern Taiwan were investigated based on geodetic and seismological data as a case study of the tectonics along a colliding plate boundary. Secular horizontal strain along the Longitudinal Valley, a probable arc-continent collision boundary between the Philippine Sea and Eurasion plates, is compressive with a large rate of 2 microstrains/year, and the maximum compression axis trends in NW-SE direction. This means that nearly two-thirds of the convergence rate between the two plates is consumed in the narrow zone along the valley and confirms the view that the valley is the plate boundary between the two. The amount of uplift in the Central Range, deduced from trigonometric leveling, reaches more than one meter during the past 60 years. Such active orogeny is caused by the high strain rate in this area. Horizontal displacement of the Coastal Range, a leading edge of the Philippine Sea plate, has a left-lateral component, suggesting that the boundary is a region of oblique collision and the range moves toward the north, producing subduction of the Philippine Sea plate off the Coast of northeastern Taiwan. An extensional strain pattern is found northeastern Taiwan near Hualien, in northern Taiwan near Ilan, and in southeastern Taiwan south Taitung. In northeastern Taiwan, the direction of the maximum extension axis is nearly parallel to the isodipth contours of deep-focus earthquakes that occurred under the southern part of the Ryukyu Trench. From a model calculation using a finite-element method, this pattern of strain is interpreted as an edge effect of the collision-subduction junction in northeastern Taiwan. The direction of the maximum extension in northern Taiwan forms high angles with the direction of the tectonic line near Ilan stretching from the Okinawa Trough. This fact is harmonious with the view that the Okinawa Trough is spreading. Extensional strain observed in southeastern Taiwan may be related to the eastward subduction since the area is situated on a transition zone, from collision to subduction.

Kosuga, Masahiro; Sato, Hiroshi; Tanaka, Torao; Sheu, Hwa Chu

1988-12-01

91

Cenozoic evolution of the Africa-Eurasia plate boundary west of Strait of Gibraltar: mechanical models based on kinematic constraints  

NASA Astrophysics Data System (ADS)

In an effort to identify the source of the 1755 Lisbon earthquake and find the missing link in the Africa-Eurasia plate boundary, extensive surveying has been going on in the Gulf of Cadiz between the Gloria Fault and the Rif-Tell boundary. The main tectonic structures in the region are(1) the allochthonous wedge of the Gulf of Cadiz and (2) a network of cross-cutting NE-SW thrusts and WNW-ESE dextral strike-slip faults. Absence of evidence for a continuous morphological frontier, combined with dispersed seismicity around the most important active thrusts, support the hypothesis that the plate boundary offshore SW Iberia corresponds to a broad (~200 km wide) zone of distributed deformation which accommodates the Africa-Eurasia convergence through dextral strike-slip along the WNW-ESE faults and synchronous oblique westwards thrusting along the NNE-SSW faults. Recently, a new swath bathymetry compilation revealed a new set of linear sub-parallel WNW-ESE trending vertical faults, estimated to be only 2 Ma old, beginning at the end of the Gloria Fault and running on for more than 600 km in the direction of the Rif-Tell plate boundary. On the whole they form a 40 km wide dextral shear band that coincides with a small circle centred on the pole of rotation of Africa with respect to Eurasia. Accordingly this fault system has been interpreted as a precursor to the formation of a new transcurrent Africa-Eurasia plate boundary. Now, if this is a new developing plate boundary the question is why is it so incipient? In fact we should ask what has been the configuration and evolution of the boundary between Africa and Eurasia in the past. Kinematic models for the motions of Africa and Iberia relative to Eurasia hold the key to the history of this plate boundary. The most recent models envisage 3 main phases in the Iberia-Africa movement during the Cenozoic: (1) between An 13 and An 6 Iberia was firmly attached to Africa in such a way that N-S compressive stresses were transmitted across the boundary causing broad intraplate deformation; (2) between An 6 and An 5 decoupling between Iberia and Africa was driven by the westward displacement of the Alboran-Betics-Rif domain; and (3) From An5 to present day Iberia is attached to Eurasia and only the westernmost parts of Iberia and Moroco are still mechanically coupled. In this study we aim to explore how the evolving plate boundary conditions throughout the Cenozoic affected the formation and/or reactivation of the main tectonic structures presently found in the Gulf of Cadiz. For that purpose we use 3D finite element models representing the three phases of the Cenozoic history of the Eurasia-Africa plate boundary. Both the convergence between the African and Iberia plates as the westward drift of the Alboran domain are considered. The plate boundary itself is defined as a set of cross-cutting cohesive zones oriented along the dominant observed structural trends. The precise locations where faults develop, among all areas modelled as cohesive zones, are determined as part of the solution. The characteristics of the fault network evolution sheds light on the configuration of the plate boundary and help to understand its present character.

Neves, M. L.; Monteiro, C.; Matias, L. M.; Rosas, F.; Terrinha, P.

2009-12-01

92

Convergence of spectral methods for hyperbolic initial-boundary value systems  

NASA Technical Reports Server (NTRS)

A convergence proof for spectral approximations is presented for hyperbolic systems with initial and boundary conditions. The Chebyshev collocation is treated in detail, but the final result is readily applicable to other spectral methods, such as Legendre collocation or tau-methods.

Gottlieb, D.; Lustman, L.; Tadmor, E.

1986-01-01

93

Finite Element Convergence for the Joule Heating Problem with Mixed Boundary Conditions  

E-print Network

We prove strong convergence of conforming finite element approximations to the stationary Joule heating problem with mixed boundary conditions on Lipschitz domains in three spatial dimensions. We show optimal global regularity estimates on creased domains and prove a priori and a posteriori bounds for shape regular meshes.

Jensen, Max

2012-01-01

94

Tsunami Signals Recorded By Plate Boundary Observatory Borehole Strainmeters  

NASA Astrophysics Data System (ADS)

The Plate Boundary Observatory (PBO), the geodetic component of the US National Science Foundation funded Earthscope program, is designed to capture the continuous three-dimensional deformation field across the western United States plate boundary. Installed and maintained by UNAVCO, the observatory currently consists of over 1100 continuous GPS sites, 6 long-baseline laser strainmeters and 75 borehole strainmeters. PBO borehole strainmeters have recorded the arrival of tsunamis generated by the 2009 M8.0 Samoa, 2010 M8.8 Chile and 2011 M9.0 Tohoku earthquakes on the Pacific coast of North America. In our analysis of the strain data we find the following: the tsunami arrival times recorded by the strainmeters are consistent with those recorded by nearby tide-gauges, the data are of sufficient quality to compare the frequency content of the tidal signal in the days before and after the tsunami and, the strain measurements are comparable with those predicted by theory. In each case the strain measurements can be translated to water height estimates which are within centimeters of those recorded by tide gauges. It is possible that borehole strainmeters could play a role in providing a land-based, continuous, high-rate tsunami measurement system.

Hodgkinson, K.; Mencin, D.; Borsa, A.; Henderson, B.; Johnson, W.

2012-04-01

95

Features on Venus generated by plate boundary processes  

NASA Technical Reports Server (NTRS)

Various observations suggest that there are processes on Venus that produce features similar to those associated with plate boundaries on earth. Synthetic aperture radar images of Venus, taken with a radar whose wavelength is 12.6 cm, are compared with GLORIA images of active plate boundaries, obtained with a sound source whose wavelength is 23 cm. Features similar to transform faults and to abyssal hills on slow and fast spreading ridges can be recognized within the Artemis region of Venus but are not clearly visible elsewhere. The composition of the basalts measured by the Venera 13 and 14 and the Vega 2 spacecraft corresponds to that expected from adiabatic decompression, like that which occurs beneath spreading ridges on earth. Structures that resemble trenches are widespread on Venus and show the same curvature and asymmetry as they do on earth. These observations suggest that the same simple geophysical models that have been so successfully used to understand the tectonics of earth can also be applied to Venus.

Mckenzie, Dan; Ford, Peter G.; Johnson, Catherine; Parsons, Barry; Sandwell, David; Saunders, Stephen; Solomon, Sean C.

1992-01-01

96

Stress accumulation and release at complex transform plate boundaries  

SciTech Connect

Finite element methods are used to model the dynamics of deformation along complex transform plate boundaries, specifically the San Andreas fault system, California. Effects of mantle rheology and fault geometry on the stress buildup and release are investigated. No prior knowledge of the earthquake cycle time or amount of fault slip is assumed that the results suggest that the San Andreas fault slips at low shear stress (about 15 MPa). Although the maximum stress on the fault is 15 MPa, models with an upper mantle shear zone deforming entirely by dislocation creep accumulate stresses that exceed 100 MPa, a stress level high enough to drive localized dynamic recrystallization and a shift in dominant deformation mechanism to diffusion creep. Models in which the mantle shear zone deform locally by diffusion creep reach a dynamic steady state where lithospheric shear stresses never exceed the specified fault stress anywhere in the model and indicate that the strength of the upper mantle is an important parameter in the dynamics of plate boundary deformation. 17 refs.

Verdonck, D.; Furlong, K.P. (Pennsylvania State Univ., University Park (United States))

1992-10-01

97

Seismotectonics and recent evolution of the Eurasia-North America Plate Boundary in Northeastern Russia  

NASA Astrophysics Data System (ADS)

In contrast to oceanic plate boundaries which are usually well defined by earthquake locations and magnetic anomalies, the present and past kinematics of plate boundaries in the continents remains problematic in many settings. One particularly vexing such boundary is the one that separates Eurasia from North America in Northeast Russia. In the earliest plate models it was evident that the mid-Atlantic spreading ridge continues in the Arctic as the Gakkel ridge which then runs almost perpendicularly into the continental shelf of Russia in the Laptev sea. On the shelf, and further south on land, the narrow belt of seismicity that is found along the Gakkel ridge broadens into a diffuse swath of earthquakes which is in places more than 800 km wide and extends along the Chersky Range towards the coast of the Okhotsk sea and northern Kamchatka The fact that the Okhotsk sea is aseismic but is surrounded by seismic belts has to lead the interpretation that it is an independent microplate that lies between the Eurasian, North American, Pacific and Amur plates (Cook et al., 1986).Unravelling the kinematics of the Eurasia-Okhotsk-North America Plate boundaries has proven difficult. This is in part due to the paucity of geological and geophysical data from this remote region, and to the fact that the Eurasia-North America pole of rotation lies in close vicinity to the plate boundary itself. Cook et al. (1986), using earthquake slip vectors, placed the current pole of rotation near the Lena river delta, that is, in the area where Eurasia-North America plate boundary comes on shore ). As a consequence, spreading along the Gakkel ridge north of the pole of rotation, should change into convergence or strike-slip to the south depending on the orientation of the boundary. Making specific predictions for fault kinematics in the area has been hampered by the fact that different geophysical and geodetic data-sets have yielded different locations for the Eurasia-North America pole of rotation (Cook et al. 1986; Rowley and Lottes, 1988; De Mets, 1990; Imaev et al., 2000; Kogan et al., 2000). Focal mechanism solutions are predominantly left-lateral and thrust along the Chersky seismic belt, that is, the northern boundary of the Okhotsk plate and right-lateral along its western boundary leading Riegel et al.(1993) to the conclusion that the Okhotsk plate is being extruded to the south. Furthermore, it has been shown on the basis of North Atlantic magnetic and gravity data, that the position of the Eurasia-North America pole of rotation moved significantly over that last 60 my so that the portion of the plate boundary in Northeast Russia changed from predominantly convergent until the Late Cretaceous to divergent until the Early Eocene, followed by various degrees of transpression during the rest of the Cenozoic (Gaina et al., 2002).On the shelf of the Laptev Sea, the Gakkel Ridge gives way to four major continental rift branches with up to 10 km of sedimentary fill spanning from the Late Cretaceous to Recent (Drachev, 1999). Earthquakes are most numerous along the southern margin of the rift system in the Lena delta region and have normal and strike-slip focal mechanism solutions (Imaev et al., 2000). On land, several branches of the rift system overprint the northern termination of the Mesozoic Verkhoyansk fold-and-thrust belt and the accreted arc terranes which are found in its hinterland (Parfenov et al., 1995). Focal mechanism solutions in this area shift from extentional to the north to compressional and strike-slip to the south. The plate boundary continues to the southeast across the Omoloi depression and then follows the trend of major mountain ranges and intermontane basins in the area: the Chersky and Moma ranges and the Moma basin. The Chersky Range, which has the highest topographic elevations in Northeast Russia (3947 m), has a complex history of Mesozoic and Cenozoic deformation (Parfenov and Gaiduk, 2001). The highest peaks are underlain by late Jurassic granite batholiths. Late Oligocene-Miocene deposits along the middle Indigirk

Imaev, V. S.; Imaeva, L. P.; Kozmin, B. M.; Fujita, K. T.; Mackey, K. G.

2009-04-01

98

Crustal motion along the Eurasia-Nubia plate boundary in the Calabrian Arc and Sicily and active extension in the Messina Straits from GPS measurements  

Microsoft Academic Search

We investigate crustal deformation along the Eurasia-Nubia plate boundary in Calabria and Sicily revealed by the GPS velocity field obtained by the combination of continuous site velocities with previous results from episodic campaigns. We recognize two distinct crustal domains characterized by different motions and styles of deformation. Convergence in Sicily is taken up by crustal shortening along the former Tyrrhenian

Nicola D’Agostino; Giulio Selvaggi

2004-01-01

99

Tectonics and plate boundary processes along the Southeast Indian Ridge and the East Pacific Rise  

Microsoft Academic Search

Classical plate tectonics describes crustal deformation in a simple kinematic way, with deformation occurring only at narrow boundaries of plates with rigid interiors. Many dynamic processes at these boundaries are not well understood. There are also apparent deviations from classical plate tectonics where significant intraplate deformation occurs. In this thesis, we analyze and model geophysical data from the Southeast Indian

James Andrew Conder

2001-01-01

100

Viscoelastic Postseismic Rebound to Strike-Slip Earthquakes in Regions of Oblique Plate Convergence  

NASA Technical Reports Server (NTRS)

According to the slip partitioning concept, the trench parallel component of relative plate motion in regions of oblique convergence is accommodated by strike-slip faulting in the overriding continental lithosphere. The pattern of postseismic surface deformation due to viscoelastic flow in the lower crust and asthenosphere following a major earthquake on such a fault is modified from that predicted from the conventual elastic layer over viscoelastic halfspace model by the presence of the subducting slab. The predicted effects, such as a partial suppression of the postseismic velocities by 1 cm/yr or more immediately following a moderate to great earthquake, are potentially detectable using contemporary geodetic techniques.

Cohen, Steven C.

1999-01-01

101

Mechanical Models of Coontinental Plate BoundariesL Fault Slip Rates and Interseismic Stress Rotation Rates.  

E-print Network

??We first describe the methodology for a two-dimensional, elastic deformable microplate modeling approach for continental plate boundaries. Deformable microplate models combine discrete slip on microplate… (more)

Langstaff, Meredith Avery

2014-01-01

102

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to: Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks Integration strategies for multiservice transport platforms Access methods that bridge traditional and emerging services Network signaling and control methodologies All-optical packet routing and switching techniques To submit to this special issue, follow the normal procedure for submission to JON, indicating "Convergence feature" in the "Comments" field of the online submission form. For all other questions relating to this feature issue, please send an e-mail to jon@osa.org, subject line &q

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2005-09-01

103

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to: Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks Integration strategies for multiservice transport platforms Access methods that bridge traditional and emerging services Network signaling and control methodologies All-optical packet routing and switching techniques

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2005-04-01

104

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to: Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks Integration strategies for multiservice transport platforms Access methods that bridge traditional and emerging services Network signaling and control methodologies All-optical packet routing and switching techniques

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2005-06-01

105

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence

Guest Editors: Thomas E. Darcie, University of Victoria Robert Doverspike, AT&T Martin Zirngibl, Lucent Technologies

Coordinating Associate Editor: Steven K. Korotky, Lucent Technologies

The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to:
  • Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks
  • Integration strategies for multiservice transport platforms

    Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

    2005-01-01

106

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to: Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks Integration strategies for multiservice transport platforms Access methods that bridge traditional and emerging services Network signaling and control methodologies All-optical packet routing and switching techniques

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2005-05-01

107

Convergence  

NASA Astrophysics Data System (ADS)

Call for Papers: Convergence The Journal of Optical Networking (JON) invites submissions to a special issue on Convergence. Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to: Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks Integration strategies for multiservice transport platforms Access methods that bridge traditional and emerging services Network signaling and control methodologies All-optical packet routing and switching techniques

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2005-08-01

108

Convergence  

NASA Astrophysics Data System (ADS)

Convergence has become a popular theme in telecommunications, one that has broad implications across all segments of the industry. Continual evolution of technology and applications continues to erase lines between traditionally separate lines of business, with dramatic consequences for vendors, service providers, and consumers. Spectacular advances in all layers of optical networking-leading to abundant, dynamic, cost-effective, and reliable wide-area and local-area connections-have been essential drivers of this evolution. As services and networks continue to evolve towards some notion of convergence, the continued role of optical networks must be explored. One vision of convergence renders all information in a common packet (especially IP) format. This vision is driven by the proliferation of data services. For example, time-division multiplexed (TDM) voice becomes VoIP. Analog cable-television signals become MPEG bits streamed to digital set-top boxes. T1 or OC-N private lines migrate to Ethernet virtual private networks (VPNs). All these packets coexist peacefully within a single packet-routing methodology built on an optical transport layer that combines the flexibility and cost of data networks with telecom-grade reliability. While this vision is appealing in its simplicity and shared widely, specifics of implementation raise many challenges and differences of opinion. For example, many seek to expand the role of Ethernet in these transport networks, while massive efforts are underway to make traditional TDM networks more data friendly within an evolved but backward-compatible SDH/SONET (synchronous digital hierarchy and synchronous optical network) multiplexing hierarchy. From this common underlying theme follow many specific instantiations. Examples include the convergence at the physical, logical, and operational levels of voice and data, video and data, private-line and virtual private-line, fixed and mobile, and local and long-haul services. These trends have many consequences for consumers, vendors, and carriers. Faced with large volumes of low-margin data traffic mixed with traditional voice services, the need for capital conservation and operational efficiency drives carriers away from today's separate overlay networks for each service and towards "converged" platforms. For example, cable operators require transport of multiple services over both hybrid fiber coax (HFC) and DWDM transport technologies. Local carriers seek an economical architecture to deliver integrated services on optically enabled broadband-access networks. Services over wireless-access networks must coexist with those from wired networks. In each case, convergence of networks and services inspires an important set of questions and challenges, driven by the need for low cost, operational efficiency, service performance requirements, and optical transport technology options. This Feature Issue explores the various interpretations and implications of network convergence pertinent to optical networking. How does convergence affect the evolution of optical transport-layer and control approaches? Are the implied directions consistent with research vision for optical networks? Substantial challenges remain. Papers are solicited across the broad spectrum of interests. These include, but are not limited to:

  • Architecture, design and performance of optical wide-area-network (WAN), metro, and access networks
  • Integration strategies for multiservice transport platforms
  • Access methods that bridge traditional and emerging services
  • Network signaling and control methodologies
  • All-optical packet routing and switching techniques

Manuscript Submission

To submit to this special issue, follow the normal procedure for submission to JON, indicating "Convergence feature" in the "Comments" field of the online submission form. For all other questions relat

Darcie, Thomas E.; Doverspike, Robert; Zirngibl, Martin; Korotky, Steven K.

2004-12-01

109

Lost in Iceland? Fracture Zone Complications Along the Mid-Atlantic Plate Boundary  

Microsoft Academic Search

The mid-Atlantic plate boundary breaks up into a series of segments across Iceland. Two transform zones, the South Iceland Seismic Zone (SISZ) and the Tjörnes Fracture Zone (TFZ) separate the on land rift zones from the Reykjanes Ridge (RR), and the Kolbeinsey Ridge (KR), offshore N-Iceland. Both are markedly different from fracture zones elsewhere along the plate boundary. The 80

B. Brandsdóttir; P. Einarsson; R. S. Detrick; L. Mayer; B. Calder; N. Driscoll; B. Richter

2003-01-01

110

Free Vibration Analysis of Kirchoff Plates with Damaged Boundaries by the Chebyshev Collocation Method  

E-print Network

Free Vibration Analysis of Kirchoff Plates with Damaged Boundaries by the Chebyshev Collocation for the free vibration analysis of slender Kirchoff plates with both mixed and damaged boundaries an important role in applications of mechanical, aerospace and civil engineering. Studying the free vibration

Butcher, Eric A.

111

Discovering Plate Boundaries Update: Builds Content Knowledge and Models Inquiry-based Learning  

Microsoft Academic Search

Discovering Plate Boundaries (DPB) is a jigsaw-structured classroom exercise in which students explore the fundamental datasets from which plate boundary processes were discovered. The exercise has been widely used in the past ten years as a classroom activity for students in fifth grade through high school, and for Earth Science major and general education courses in college. Perhaps more importantly,

D. S. Sawyer; M. S. Pringle; A. T. Henning

2009-01-01

112

INTRODUCTION The northern Australia plate boundary (Figure 1) is a com-  

E-print Network

history. Plate motion models indicate that Australia has moved rapidly north since the Eocene reconstructions (de Jonge et al. 1994; Bunge & Grand 2000; Hafkenscheid et al. 2001). Conversely, plate-tectonicINTRODUCTION The northern Australia plate boundary (Figure 1) is a com- plex and actively deforming

Royal Holloway, University of London

113

The role of positive boundary data in generalized clamped plate equations  

E-print Network

subtle. It depends on the domain and on the particular form of the operator whether there are com dimensions (1) is the clamped plate equation. Here is the shape of the plate, f is the perpendicular load, the boundary data and describe the "clamping" and u is the deflection of the plate. Most authors concentrated

Grunau, Hans-Christoph

114

Subcrustal earthquakes in the plate boundary zone of New Zealand's South Island  

NASA Astrophysics Data System (ADS)

Sporadic, intermediate-depth earthquakes have been observed for ~40 years in the vicinity of the Alpine Fault, a 460 km-long transpressive fault forming the western boundary of the Southern Alps. The Alpine Fault represents the plate boundary between the Australian and Pacific Plates in New Zealand and links two subduction zones of opposite polarity in the North and South. Several earthquakes at depths of 59-85 km have been recorded by the Southern Alps Microearthquake Borehole Array (SAMBA) since its deployment in November 2008. Due to large numbers of impulsive phase arrivals, focal mechanisms were obtained for these events during routine processing. In 2009 and early 2010, several additional temporary seismometer networks were operating in the central Southern Alps (Alpine Fault Array ALFA, Deep Fault Drilling Project 2010 DFDP10) and the offshore region west of the South Island (Marine Observations of Anisotropy Near Aotearoa MOANA). To gain more insight about the cause and mechanism of these deep events, a comprehensive analysis has been performed incorporating data from all available instruments. Accurate hypocentres of 22 earthquakes (ML<4) and focal mechanisms of at least 14 events have been obtained. The focal mechanisms reveal that reverse faulting predominates at depth in the continental collision zone between the Pacific and Australian Plates. The intermediate-depth events occur below the Moho discontinuity, which has been mapped in detail using wide-angle reflection/refraction data obtained during the South Island Geophysical Transect (SIGHT) project in 1995/96. Although the cause for these subcrustal earthquakes is not yet clear, they have previously been interpreted to result from intra-continental subduction (Reyners 1987), high shear-strain gradients due to depressed geotherms and viscous deformation of mantle lithosphere (Kohler and Eberhart-Phillips 2003). On the basis of the locations and mechanisms obtained using SAMBA, we have argued that these events are caused due to high strain rates resulting from plate bending, but this is the subject of further investigations. Reyners, M., Subcrustal earthquakes in the central South Island, New Zealand, and the root of the Southern Alps, Geology, 15, 1168-1171, 1987. Kohler, M., and D. Eberhart-Phillips, Intermediate-depth earthquakes in a region of continental convergence: South Island, New Zealand, Bulletin of the Seismological Society of America, 93 , 85, 2003.

Boese, C. M.; Stern, T. A.; Townend, J.; Sheehan, A. F.; Molnar, P. H.; Collins, J. A.; Karalliyadda, S.; Bourguignon, S.; Bannister, S. C.

2012-12-01

115

A visual study of vortex-induced subcritical instability on a flat plate laminar boundary layer  

Microsoft Academic Search

This paper reports results of our experimental investigation on flow instability on a flat plate laminar boundary layer caused by a “captive” vortex migrating far outside the boundary layer. Results show that the sign of the circulation associated with the vortex is the main determinant for the severity of the boundary layer instability. A captive vortex with an opposite sign

T. T. Lim; T. K. Sengupta; M. Chattopadhyay

2004-01-01

116

The Earthscope Plate Boundary Observatory Akutan Alaskan Volcano Network Installation  

NASA Astrophysics Data System (ADS)

During June and July of 2005, the Plate Boundary Observatory (PBO) installed eight permanent GPS stations on Akutan Volcano, in the central Aleutian Islands of Alaska. PBO worked closely with the Alaska Volcano Observatory and the Magmatic Systems Site Selection working group to install stations with a spatial distribution to monitor and detect both short and long term volcanic deformation in response to magmatic intrusions at depth and magma migration through the volcano's conduit system. All eight of the GPS stations were installed by PBO field crews with helicopter support provided by Evergreen Helicopters and logistical support from the Trident Seafood Corporation, the City of Akutan, and the Akutan Corporation. Lack of roads and drivable trails on the remote volcanic island required that all equipment be transported to each site from the village of Akutan by slinging gear beneath the helicopter and internal loads. Each station installed on the volcano consists of a standard short braced GPS monument, two solar panels mounted to an inclined structure, and a six foot high Plaschem enclosure with two solar panels mounted to one of the inclined sides. Each Plaschem houses 24 6 volt batteries that power a Trimble NetRS GPS receiver and one or two Intuicom radios. Data from each GPS receiver is telemetered directly or through a repeater radio to a base station located in the village of Akutan that transmits the data over the internet to the UNAVCO data archive at ftp://data-out.unavco.or/pub/PBO_rinex where it is made freely available to the public.

Pauk, B.; Jackson, M.; Mencin, D.; Power, J.; Gallaher, W.; Basset, A.; Kore, K.; Hargraves, Z.; Peterson, T.

2005-12-01

117

Interaction between the Dauki and the Indo-Burman convergence boundaries from teleseismic and locally recorded earthquake data  

NASA Astrophysics Data System (ADS)

The Himalayan and the Burma Arcs converge onto the Indian plate from opposite sides near their syntaxial juncture and have reduced it to a sliver. Both geology and seismicity point to recent internal deformation and high seismogenic potential within this sliver. Large historical earthquakes, including the Great Indian earthquake of 1897 (Mw ~8.1), along with the recent seismicity, suggest that the cratonic blocks in the region are bounded by active faults. The most prominent is the E-W trending Dauki Fault, a deeply-rooted, north-dipping thrust fault, situated between the Shillong massif to the north and the Sylhet Basin to the south. Along the Burma Arc, the subducted seismogenic slab of the Indian plate is continuous north to the syntaxis. Yet the Naga and Tripura segments of the accretionary fold belt, respectively north and south of the easterly extrapolation of the Dauki fault, are distinct. Accretion has advanced far westward into the foredeep of the Dauki structure along the front of the Tripura segment, while it has remained stunted facing the uplifted Shillong massif along the Naga segment. Moreover, the Dauki topographic front can be traced eastwards across the Burma Arc separating the two segments. Recent earthquakes support the hypothesis that the Dauki convergence structure continues below the Burma accretionary belt. Using teleseismic and regional data from the deployment of a local network, we explore the interaction of the Dauki thrust fault with the Burma Arc subduction zone. Preliminary observations include: While seismicity is concentrated in the slab at the eastward extrapolation of the Dauki fault, shallow seismicity is diffuse and does not illuminate the Dauki fault itself. P-axes in moment-tensor solutions of earthquakes within the Indian plate tend to be directed N-S and are locally parallel to the India-Burma boundary, particularly in the slab. T-axes tend to be oriented E-W with a strong tendency to follow the slab down dip. This pattern is remarkably consistent, despite the scattered seismicity, and suggests that the stress in the Indian plate, including the subducted oceanic portion of the plate, is still primarily controlled by the Himalayan collision to the north and down-dip pull by the Burma slab. Moment tensor solutions for some of the shallow earthquakes along the fold belt are consistent with geodetic results, showing partitioning of the oblique India-Burma convergence between belt-parallel dextral faults and belt-normal shortening by thrust faults. Relocations of the events using the double-difference algorithm may provide additional constraints on the geometry of the slab. In addition to the analysis of teleseismic data, a network of six seismic stations was also installed in Bangladesh in the region surrounding Sylhet, south of the Shillong Plateau during 2007-2008. Over 200 regional and local events are detected and located by the Sylhet array. About a dozen events are large enough allowing us to determine focal depths and mechanisms that will augment the catalog of the teleseismic events, providing additional insights into the tectonics in the region.

Howe, M.; Moulik, P.; Seeber, L.; Kim, W.; Steckler, M. S.

2012-12-01

118

A plate tectonic model for the Paleozoic and Mesozoic constrained by dynamic plate boundaries and restored synthetic oceanic isochrons  

NASA Astrophysics Data System (ADS)

We developed a plate tectonic model for the Paleozoic and Mesozoic (Ordovician to Cretaceous) integrating dynamic plate boundaries, plate buoyancy, ocean spreading rates and major tectonic and magmatic events. Plates were constructed through time by adding/removing oceanic material, symbolized by synthetic isochrons, to major continents and terranes. Driving forces like slab pull and slab buoyancy were used to constrain the evolution of paleo-oceanic domains. This approach offers good control of sea-floor spreading and plate kinematics. This new method represents a distinct departure from classical continental drift reconstructions, which are not constrained, due to the lack of plate boundaries. This model allows a more comprehensive analysis of the development of the Tethyan realm in space and time. In particular, the relationship between the Variscan and the Cimmerian cycles in the Mediterranean-Alpine realm is clearly illustrated by numerous maps. For the Alpine cycle, the relationship between the Alpides senso stricto and the Tethysides is also explicable in terms of plate tectonic development of the Alpine Tethys-Atlantic domain versus the NeoTethys domain.

Stampfli, G. M.; Borel, G. D.

2002-02-01

119

Inter- and intra-plate deformation at North American plate boundaries  

NASA Technical Reports Server (NTRS)

Alaska tectonics and earthquake hazard studies; Southern California tectonics (block rotation); spreading near the Salton Trough; California plate motion (fault zone kinematics); and Caribbean plate motion investigations are examined.

Beavan, John

1986-01-01

120

Recovering physical property information from subduction plate boundaries using 3D full-waveform seismic inversion  

NASA Astrophysics Data System (ADS)

Our understanding of subduction margin seismogenesis has been revolutionised in the last couple of decades with the discovery that the size of the seismogenic zone may not be controlled simply by temperature and a broad spectrum of seismic behaviour exists from stick-slip to stable sliding. Laboratory and numerical experiments suggest that physical properties, particularly fluid pressure may play an important role in controlling the seismic behaviour of subduction margins. Although drilling can provide information on physical properties along subduction thrust faults at point locations at relatively shallow depths, correlations between physical properties and seismic velocity using rock physics relationships are required to resolve physical properties along the margin and down-dip. Therefore, high resolution seismic velocity models are key to recovering physical property information at subduction plate boundaries away from drill sites. 3D Full waveform inversion (FWI) is a technique pioneered by the oil industry to obtain high-resolution high-fidelity models of physical properties in the sub-surface. 3D FWI involves the inversion of low-frequency (>2 to <7 Hz), early arriving (principally transmitted) seismic data, to recover the macro (intermediate to long-wavelength) velocity structure. Although 2D FWI has been used to improve velocity models of subduction plate boundaries before, 3D FWI has not yet been attempted. 3D inversions have superior convergence and accuracy, as they sample the subsurface with multi-azimuth multiply-crossing wavefields. In this contribution we perform a suite of synthetic tests to investigate if 3D FWI could be used to better resolve physical property information along subduction margin plate boundaries using conventionally collected 3D seismic data. We base our analysis on the Muroto Basin area of the Nankai margin and investigate if the acquisition parameters and geometry of the subduction margin render 3D seismic data collected across this basin in 1999 suitable for future 3D FWI. We build a 3D model of the sub-surface based on an existing velocity model that was used to migrate these data (Tsuji et al. 2000, JGR). We then add a low P-wave velocity layer along the décollement, which is supported by ODP core data but does not feature in the current seismic velocity model, to test if it could be recovered using 3D FWI. We use the same acquisition parameters as in the 1999 seismic survey (including a 6 km long streamer) to generate a fully-elastic synthetic seismic dataset, added noise and inverted the windowed transmitted arrivals only. We also ran a suite of resolution tests across the model. The results show that 3D FWI of conventionally collected 3D seismic data across the Muroto Basin would be capable of resolving variations in P-wave velocity along the décollement of the order of half the seismic wavelength at the plate boundary. This is a significant improvement on conventional travel-time tomography which resolves to the Fresnel width. In this presentation we will also postulate on the optimal 3D FWI experiment design for the next generation of 3D seismic surveys across subduction margins as a guide for those embarking on new data collection.

Bell, R. E.; Morgan, J. V.; Warner, M.

2013-12-01

121

Extension along the Australian-Pacific transpressional transform plate boundary near Macquarie Island  

Microsoft Academic Search

The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex (MRC), south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present-day curvature of the transform is inherited from a preexisting divergent plate boundary and that the

Nathan R. Daczko; Karah L. Wertz; Sharon Mosher; Millard F. Coffin; Tip A. Meckel

2003-01-01

122

Extension Along the Australian-Pacific Transpressional Transform Plate Boundary Near Macquarie Island  

Microsoft Academic Search

The Australian-Pacific transform plate boundary fault zone along the Macquarie and McDougall segments of the Macquarie Ridge Complex, south of New Zealand, is characterized by dominantly normal faults and pull-apart basins, in apparent conflict with the regional transpressional tectonic setting. We propose that present day curvature of the transform is inherited from a preexisting divergent plate boundary and that the

N. R. Daczko; K. L. Wertz; S. Mosher; M. F. Coffin

2002-01-01

123

Understanding Plate Motions  

NSDL National Science Digital Library

This interactive site uses illustrations and photographs along with text to explain the movement of tectonic plates and the result of this movement on the surface of the Earth. There is a detailed discussion of the movement at each of the four types of plate boundaries: divergent, convergent, transform, and plate boundary zones. Both lateral and vertical movements are depicted by maps and diagrams and resulting Earth structures are shown in photographs.

124

Radiocarbon evidence for extensive plate-boundary rupture about 300 years ago at the Cascadia subduction zone  

USGS Publications Warehouse

THE Cascadia subduction zone, a region of converging tectonic plates along the Pacific coast of North America, has a geological history of very large plate-boundary earthquakes1,2, but no such earthquakes have struck this region since Euro-American settlement about 150 years ago. Geophysical estimates of the moment magnitudes (Mw) of the largest such earthquakes range from 8 (ref. 3).to 91/2 (ref. 4). Radiocarbon dating of earthquake-killed vegetation can set upper bounds on earthquake size by constraining the length of plate boundary that ruptured in individual earthquakes. Such dating has shown that the most recent rupture, or series of ruptures, extended at least 55 km along the Washington coast within a period of a few decades about 300 years ago5. Here we report 85 new 14C ages, which suggest that this most recent rupture (or series) extended at least 900 km between southern British Columbia and northern California. By comparing the 14C ages with written records of the past 150 years, we conclude that a single magnitude 9 earthquake, or a series of lesser earthquakes, ruptured most of the length of the Cascadia subduction zone between the late 1600s and early 1800s, and probably in the early 1700s.

Nelson, A. R.; Atwater, B. F.; Bobrowsky, P. T.; Bradley, L. -A.; Clague, J. J.; Carver, G. A.; Darienzo, M. E.; Grant, W. C.; Krueger, H. W.; Sparks, R.; Stafford, Jr. , T. W.; Stuiver, M.

1995-01-01

125

Evolving deformation along a transform plate boundary: Example from the Dead Sea Fault in northern Israel  

NASA Astrophysics Data System (ADS)

We analyzed geologic structures adjacent to the Dead Sea Fault (DSF) along the margins of the Sinai and Arabian plates in northern Israel in order to investigate the style and sequence of deformation associated with a transform plate boundary. The field area, located between the Hula basin in northern Israel and the Lebanese restraining bend in southern Lebanon, is divided into distinct structural blocks by a series of distributed faults that comprise this approximately N-S trending section of the DSF. Cretaceous and Tertiary rocks within and adjacent to the structural blocks are folded into broad anticlines and synclines, with more intense localized shortening manifested by tight folds and thrust duplexes. Kinematic analyses of folds, faults, and veins provide evidence for two directions of regional shortening: (1) NW-SE shortening responsible for the formation of NE-SW trending fold axes and left-lateral strike-slip motion along N-S trending faults and (2) E-W shortening as indicated by N-S trending fold axes, N-S striking thrust faults, and extensional calcite-filled veins that strike E-W. Crosscutting relations and U-Th ages of the vein material suggest that the E-W phase of transform-normal shortening represents the most recent and presently active phase of deformation. The structural analysis provides evidence for the transition from an early (Miocene-lower Pliocene) phase of pure strike-slip motion to a late (Pleistocene to Recent) phase of convergent strike slip. The latter phase is characterized by strain partitioning, which is manifested by discrete left-lateral strike-slip motion across weak N-S faults and the development of a fold-thrust belt in response to transform-normal shortening. Analogous to the strain partitioning observed in southern California, we suggest that blind thrust faults adjacent to the DSF in the study area may pose a seismic risk to populations in northern Israel and southern Lebanon.

Weinberger, Ram; Gross, Michael R.; Sneh, Amihai

2009-10-01

126

Gas-phase boundary layer ignition on a catalytic flat plate with heat loss  

Microsoft Academic Search

The gas-phase ignition of a premixed boundary layer flow by a nonisothermal plate with very large catalytic efficiency is studied. The catalytic upper side of the plate is in contact with the premixed gas while the lower side is held at constant temperature. The catalytic reaction is assumed to be ignited and diffusion controlled. The temperature on this side changes

C. Trevino; N. Peters

1985-01-01

127

Design of Steel Plate Shear Walls Considering Boundary Frame Moment Resisting Action  

E-print Network

Design of Steel Plate Shear Walls Considering Boundary Frame Moment Resisting Action Bing Qu, M.ASCE1 ; and Michel Bruneau, M.ASCE2 Abstract: Conventional design of steel plate shear walls SPSWs using validated models are presented to compare the seismic performances of SPSWs designed using

Bruneau, Michel

128

DESIGN OF STEEL PLATE SHEAR WALLS CONSIDERING BOUNDARY FRAME MOMENT RESISTING ACTION  

E-print Network

DESIGN OF STEEL PLATE SHEAR WALLS CONSIDERING BOUNDARY FRAME MOMENT RESISTING ACTION B. Qu1 and M.Bruneau2 ABSTRACT Conventional design of steel plate shear walls (SPSWs) assumes that 100% of the story are presented to compare the seismic performances of SPSWs designed using different design assumptions

Bruneau, Michel

129

Pore fluid pressures, porosity, and permeability of the Cascadia subduction zone plate boundary  

Microsoft Academic Search

The strength and seismogenic behavior of subduction zone plate boundaries depend critically on pore fluid pressure. Integrated over time, large amounts of H2O are released from subducting plates by tectonic compaction at shallow depths and by metamorphic dehydration reactions at deeper depths. In the Cascadia subduction zone, beneath southern Vancouver Island, converted teleseismic waves reveal anomalously high Poisson's ratios (average

S. M. Peacock; N. I. Christensen; M. G. Bostock; P. Audet

2009-01-01

130

The role of positive boundary data in the clamped plate equation, perturbation results and other generalizations  

E-print Network

; # ## #19; u|## = #, (1) yield positive solutions u # 0. Here# # R n is the ``shape of the plate, # and # are the boundary data and u is the deflection of the ``plate''. Most authors concentrated on the Green function G 2#erential operator and in [GS2] with respect to the domain and the highest order terms of the di#erential operator

Sweers, Guido

131

The role of positive boundary data in generalized clamped plate equations  

E-print Network

form of the operator whether there are com- parison principles or not. Until now most papers dimensions (1) is the clamped plate equation. Here is the shape of the plate, f is the perpendicular load, * *the boundary data ' and _ describe the "clamping" and u is the deflection of the pl* *ate. Most

Grunau, Hans-Christoph

132

The role of positive boundary data in the clamped plate equation, perturbation results and other generalizations  

E-print Network

is the "shape of the plate" (physic* *ally relevant for n = 2), is the exterior unit normal at @ , f is the (perpendicular) load,* * ' and _ are the boundary data and u is the deflection of the "plate". Most authors* * respect to lower order terms of the differential operator and in [GS2 ] with respect to th* *e domain

Sweers, Guido

133

Inter- and intra-plate deformation at North American plate boundaries  

NASA Technical Reports Server (NTRS)

A geodetic network which spans the region between San Francisco and Lake Tahoe has been measured 5 times completely with triangulation in 1880, 1922, 1929, 1943, 1963. A resurvey with the Global Positioning System (GPS) in 1991 allows the formation of 1 coseismic and 4 interseismic epochs. The data from this network provide a unique opportunity to examine the temporal and spatial evolution of the strain field associated with the 1906 San Francisco earthquake in particular and with the Pacific-North American plate boundary in general. Calculations of strain rate from the network data lead to the following conclusions. (1) There is no resolvable (greater than 0.05 microradians/yr) strain in between Sutter Buttes and the Sierra Nevada. (2) Throughout the time since the 1906 earthquake, a region extending at least as far east as the westernmost Great Valley has been undergoing deformation related to Pac:Nam interaction and the associated earthquake cycle. (3) In the time and space of overlap, our results agree with those from the United States Geological Survey (USGS) trilateration data. Both data sets indicate that strain must be accumulating to the east of Vaca. (4) The San Andreas discrepancy cannot be accommodated in the Great Valley at the 1 sigma level of our results. It is possible to absorb it in that region at the 2 sigma level. (5) Strain rate is elevated in the years following the earthquake and decays slowly with time. It is possible that the rate in the Coast Ranges increases until around 1950 and then decays. With the exception of one epoch, strain rate in the Coast Ranges is consistently fault parallel, shows no sign changes, and is consistent with monotonic strain accumulation.

Beavan, John; Gilbert, Lewis E.; Scholz, Chris

1992-01-01

134

Rapidly converging iterative schemes for volterra integral equations an application to problem in boundary-layer theory  

SciTech Connect

Iterative schemes converging monotonically and uniformly to the unique solution of nonlinear Volterra integral equation are developed, under various monotonicity and convexity (concavity) conditions on the kernel. The rate of convergence of the schemes is quadratic or higher, and hence rapid. An application to problem arising in connection with the boundary-layer flow past a half plane is given, and examples illustrating the results are presented.

Pandit, S.G. [Winston-Salem State Univ., NC (United States)

1994-12-31

135

Flat-Plate Boundary Layer Receptivity to a Steady Free-Stream Vortex Disturbance  

Microsoft Academic Search

A single trailing vortex developed behind a micro-wing immersed in a free stream was used to study the vortex receptivity of the boundary layer on a flat plate. As a result of the interaction, in the boundary layer there develop longitudinal-velocity disturbances which grow almost linearly in the longitudinal coordinate. The parameters of the excited steady disturbances agree with the

A. V. Boiko

2001-01-01

136

Scattered waves from low-frequency earthquakes and plate boundary structure in northern Cascadia  

E-print Network

boundary structure of the Cascadia subduction zone and previ- ous work on the detection and location the subduction zone structure and constrain the location of LFEs relative to the plate boundary. 2. Cascadia Low. To account for crustal velocity heterogeneity, a smoothed 3-D model of subduction zone structure is assembled

Nowack, Robert L.

137

Receptivity of the Flat-Plate Boundary Layer to Free-Stream Turbulence  

Microsoft Academic Search

The linear problem of generation of perturbations of a flat-plate boundary layer by external turbulence is solved. The turbulence is represented in the form of a set of space- and time-periodic vortex modes. It is shown that the boundary layer is most receptive to low-frequency longitudinal vorticity modes. The mean-square velocity fluctuations in the boundary layer and their spectrum are

M. V. Ustinov

2003-01-01

138

The International Plate Boundary Observatory Chile (IPOC) in the northern Chile seismic gap  

NASA Astrophysics Data System (ADS)

Fast convergence between the oceanic Nazca and the continental South American plate is accommodated by recurrent rupture of large segments of the two plates' interface. The resulting earthquakes are among the largest and, for their sizes, most frequent on Earth. Along the Chilean and southern Peruvian margin, all segments have ruptured at least once in the past 150 years for which there exist historic and/or instrumental records. The one segment that is most mature for re-rupture stretches for more than 500 km along the northernmost Chilean coast between roughly -23° and -18° latitude. It last broke in 1877 in a magnitude ~8.8 earthquake, triggering a major Tsunami. From the historical record, it has been known to have a recurrence cycle of approximately 110 years. The adjoining segments to the north and south broke rather recently in 1995 and 2001 in M>8 earthquakes and an M 7.7 earthquake encroached the southern part of the gap in 2007. The IPOC project intends to investigate this segment of the Nazca-South American plate boundary, on which a strong to devastating earthquake is expected to occur within the next years, by monitoring at a variety of time-scales deformation, seismicity, and magnetotelluric fields in the subduction zone at the closing stages of the interseismic cycle before and possibly during occurrence of a big earthquake. For that purpose, installation of long-term observatories in Northern Chile started in 2006 in a close cooperation of the Universidad de Chile (Santiago, Chile), the Universidad Catolica del Norte (Antofagasta, Chile), the Institut de Physique du Globe de Paris (Paris, France), and the German Research Centre for Geosciences (GFZ, Potsdam, Germany). Currently we are operating 14 modern seismological stations equipped with STS-2 broadband seismometers and accelerometers (EPI sensor). At least two more stations will be installed in the near future. To cope with the high resolution and dynamic of the sensors and data acquisition, site installation was accomplished with special care. At each station a cavern was blasted into the bedrock up to 5 meters deep to ensure stable conditions for measurements. Currently five stations are additionally recording continuously GPS signals, another five are also recording meteorological data, and another seven are equipped with Magneto-Telluric (MT) probes (fluxgate magnetometers and electrode lines). It is planned to extend the multi-parameter observation to as many stations as possible. So far ten of the stations are sending continuous data via satellite links (VSAT) to the GEOFON data host at the GFZ. We will be reporting first results on seismicity, transient deformation and MT from the first two years of recording.

Schurr, B.; Asch, A.; Sodoudi, F.; Manzanares, A.; Ritter, O.; Klotz, J.; Chong-Diaz, G.; Barrientos, S.; Villotte, J.-P.; Oncken, O.

2009-04-01

139

Microplate kinematics, strain accumulation and geodetic fault slip rates along the Sicily-Calabria segment (southern Italy) of the Nubia-Eurasia plate boundary from the analysis and modeling of dense GPS networks  

Microsoft Academic Search

The Sicily and Calabria regions (Southern Italy) are among the most seismically active areas of the Mediterranean basin. The highest seismic moment rates align along the Calabro-Peloritani arc, a tectonically complex segment of the central Mediterranean plate boundary zone, whose Neogene to Quaternary evolution is generally interpreted in terms of slow relative Africa-Eurasia plate convergence and fast subduction and roll-back

B. Mastrolembo Ventura; E. Serpelloni; R. Burgmann; P. Baldi

2010-01-01

140

On Boundary Control Problems in Slow Processes for Piezothermoelastic Plates  

E-print Network

We consider a piezothermoelastic panel occupied by a material of hexagonal crystal class. We study the response when the boundary conditions vary very slowly with time and one of the bounding faces is subject to thermal exposure. We show that in some cases the temperature on the other bounding face can be controlled by the difference of electric potential between the faces.

Adriano Montanaro

2008-08-07

141

Velocity Distribution in the Boundary Layer of a Submerged Plate  

NASA Technical Reports Server (NTRS)

This report deals with the measurement of the velocity distribution of the air in the velocity of a plate placed parallel to the air flow. The measurements took place in a small wind tunnel where the diameter of the entrance cone is 30 cm and the length of the free jet between the entrance and exit cones is about 2.5 m. The measurements were made in the free jet where the static pressure was constant, which was essential for the method of measurement used.

Hansen, M

1930-01-01

142

Kinematics to dynamics in the New Zealand plate-boundary zone  

NASA Astrophysics Data System (ADS)

New Zealand straddles the boundary between the Australian and Pacific plate, with a transition from subduction of Pacific plate oceanic lithosphere in the North, beneath North Island to oblique continental collision in South Island. Cenozoic relative plate motion has resulted in a complex pattern of faulting and block rotation in a zone up to 250 km wide, with displacements on individual faults up to 100s of kilometres. Here, I use a compilation of seismic reflection/refraction studies and high quality receiver function analyses, together with simple Airy isostasy, to determine the regional crustal and mantle structure. The buoyancy stress in the deforming layer is calculated by integrating the vertical normal stress with depth. This, in combination with plate-boundary stresses, must drive deformation. Horizontal gradients of buoyancy stress can be compared with horizontal gradients of strain rate, using the method of England & Molnar (1997), in the context of a simple thin sheet model of lithospheric deformation. I derive a velocity field for the New Zealand plate-boundary zone, using the method of Lamb (2000). This is representative of deformation over tens of thousands of years, based on fault slip, strain rate azimuth and paleomagnetic data, in the context of the short term relative plate motions. Comparison of appropriate combinations of horizontal gradients of vorticity and dilatation with horizontal gradients of buoyancy stress shows that deformation has some of the features of a Newtonian fluid. In detail, the minima in buoyancy stress, calculated from the vertical density structure, are offset horizontally from that calculated from gradients of strain rate, suggesting strong lateral contrasts in viscosity if deformation is strongly coupled at all levels in the lithosphere, with viscosities in the range 1 - 10 x 10**21 Pa s. However, subduction of Pacific plate lithosphere along the Hikurangi margin, and evidence for underthrusting beneath the Southern Alps, implies decoupling of deformation at depths > 50 km in these regions. In this case, best-fit viscosities for the top 50 km are in the range 1 - 5 x 10**21 Pa s. Given the characteristic strain rates in the plate-boundary zone, all these viscosities imply plate-boundary deviatoric stresses generally < 20 MPa, and are consistent with previous low estimates of shear stresses on the subduction plate interface based on a simple force balance (Lamb 2006). Fluid-like behaviour of the New Zealand plate-boundary zone is consistent with both geodetic data and the observed pattern of shear wave splitting. References: England, P.C., and P. Molnar, Science, 278, 647-649, 1997. Lamb, S., JGR, 105, 25,627-25,653, 2000. Lamb, S., JGR, 111, B07401, doi:10.1029/2005JB003916, 2006.

Lamb, Simon

2014-05-01

143

Effects of boundary slippage on thin-film lubrication between two nonparallel plane plates  

NASA Astrophysics Data System (ADS)

Hydrodynamic lubrications between two plane plates with an intersection angle ? have been investigated using the boundary slippage theory, and relations are obtained between dimensionless pressures and coordinate x, between bearing capacity, friction force, friction coefficient and dimensionless slipping size factor. The results show that bearing capacity of two plane plates without boundary slippage significantly increases with increasing intersection angle ? when 0 < ? < 1°, whereas decreases with increasing intersection angle ? when ? > 1°. The results also show that negative pressure occurs in fluid entrance region and bearing capacity decreases, and friction force and friction coefficient increase with the increase of dimensionless slipping size factor.

Ban, Shu-Hao; Li, Xiao-Yan

2012-06-01

144

Boundary-layer transition on a plate subjected to simultaneous spanwise and chordwise pressure gradients  

NASA Technical Reports Server (NTRS)

The boundary-layer transition on a short plate was studied by means of the china-clay visual technique. The plate model was mounted in a wind tunnel so that it was subjected to small simultaneous spanwise and chordwise pressure gradients. Results of the experimental study, which was performed at three subsonic velocities, indicated that the transition pattern was appreciably curved in the spanwise direction but quite smooth and well behaved. Reasonable comparisons between predictions of transition and experiment were obtained from two finite-difference two-dimensional boundary-layer calculation methods which incorporated transition models based on the concept of a transition intermittency factor.

Boldman, D. R.; Brinich, P. F.

1974-01-01

145

Continent-continent collision at the Pacific/Australian plate boundary: Lithospheric deformation, mountain building, and subsequent scientific endeavors  

NASA Astrophysics Data System (ADS)

Continental collision occurs at strike-slip plate boundaries where transform motion and oblique convergence create processes of surficial mountain building and deformation within the deeper crust and lithospheric mantle. The Pacific/Australian transform plate boundary in South Island, New Zealand, is characterized by active oblique continent-continent collision with an associated Southern Alps orogen that exhibits both high exhumation rates and rapid strike-slip movement. Beginning in the 1990s, this system was the focus of a decade-long collaborative USA-New Zealand multi-disciplinary study to understand lithospheric structure and processes involved in this transpression. Funded primarily by the NSF Continental Dynamics program and the New Zealand Science Foundation, this project known as SIGHT (South Island Geophysical Transect) with its companion SAPSE (Southern Alps Passive Seismic Experiment) included the following disciplines that involved substantial field observation experiments: seismic reflection, explosion refraction, onshore-offshore wide-angle reflection/refraction, regional and teleseismic passive seismology, magnetotellurics, laboratory petrophysics, gravity, regional geological investigations, and rheological analyses. More than fifty scientists and students from both nations participated in the combined set of studies that have led to over forty-five journal publications, an AGU Monograph, and a dozen graduate theses. Primary results of the project indicate the Pacific-Australian strike-slip plate boundary (Alpine fault) is not vertical but is eastward dipping and rheologically weak based on diverse geophysical data. Most deformation is within the Pacific plate that hosts the Southern Alps orogen. High mantle seismic velocities vertically disposed beneath the orogen suggest Pacific and perhaps Australian mantle lithosphere contribute to a zone of plate-boundary-parallel distributed mantle shortening. The crustal root of the overlying Southern Alps is larger than needed to support surface topography, and is offset from its topographic high, consistent with dynamic thickening of the Pacific crust by the mantle thickening. Teleseismic shear wave splitting is evidence of a wide zone of distributed strain for the mantle portion of the plate boundary. The collective set of results from the South Island projects have led to a number of subsequent studies by various teams, based on follow-up questions, expanded observational expertise, and international collaborative alliances with in particular the New Zealand science community. These studies include a search for the full width of Pacific/Australian distributed mantle strain using marine OBS studies, the transition from strike-slip to plate boundary subduction to the north, the search and discovery of seismic tremor on the Alpine fault, and high resolution geophysical characterization of Alpine fault seismogenesis. The success of geophysically imaging a narrow island using both marine sides led different SIGHT scientists to carry out expanded efforts to study North Island subduction and separately Taiwan mountain building. These efforts benefited and were largely motivated from multi-disciplinary, multi-national collaborations as typically supported by the NSF Continental Dynamics program.

Okaya, D. A.; Stern, T. A.; Davey, F. J.

2012-12-01

146

A model of convergent plate margins based on the recent tectonics of Shikoku, Japan  

NASA Technical Reports Server (NTRS)

A viscoelastic finite element plate tectonic model is applied to displacement data for the island of Shikoku, Japan. The flow properties and geometry of the upper portions of the earth are assumed known from geophysical evidence, and the loading characteristics are determined from the model. The nature of the forces acting on the Philippine Sea plate, particularly in the vicinity of the Nankai trough, is determined. Seismic displacement data related to the 1946 Nankaido earthquake are modeled in terms of a thick elastic plate overlying a fluidlike substratum. The sequence of preseismic and seismic displacements can be explained in terms of two independent processes operating on elastic lithospheric plates: a strain accumulation process caused by vertical downward forces acting on or within the lithosphere in the vicinity of the trench, and a strain release process caused by plate failure along a preexisting zone on weakness. This is a restatement of Reid's elastic rebound theory in terms of elastic lithospheric plates.

Bischke, R. E.

1974-01-01

147

Convergent boundaries and related igneous and metamorphic complexes in caledonides of Central Asia  

NASA Astrophysics Data System (ADS)

Fragments of the crystalline complexes where Vendian metamorphism of moderate and elevated pressure predated Early Paleozoic metamorphism have been established in the accretionary-collisional domain of the eastern segment of the Central Asian Foldbelt (Early Caledonian superterrane of Central Asia). The geodynamic setting of the Vendian (˜560-570 Ma) South Hangay metamorphic belt located in the junction zone of the Baydrag Block and the Late Riphean (˜665 Ma) ophiolite complex of the Bayanhongor Zone is considered. The origination of this belt was related to the formation of the convergent boundary in the framework of the Zabhan microcontinent about 570 Ma ago. At the same time, an island-arc complex was formed in the paleo-oceanic domain. Metamorphism of elevated pressure indicates that Vendian structures with sufficiently thick continental crust were formed in the framework of the continental blocks. Vendian metamorphism is also established in the Tuva-Mongolia Massif and the Kan Block of the Eastern Sayan. These data show that the Late Baikalian stage predated the evolution of the Early Caledonian superterrane of Central Asia. The development of its accretionary-collisional structure was accompanied by Late Cambrian-Early Ordovician low-pressure regional metamorphism. Granulite-facies conditions were reached only at the deep levels of the accretionary-collisional edifice. The outcrops of crystalline complexes in the southern framework of the Caledonian paleocontinent are regarded as fragments of the Early Paleozoic Central Mongolian metamorphic belt.

Kozakov, I. K.; Sal'Nikova, E. B.; Yarmolyuk, V. V.; Kozlovsky, A. M.; Kovach, V. P.; Azimov, P. Ya.; Anisimova, I. V.; Lebedev, V. I.; Enjin, G.; Erdenejargal, Ch.; Plotkina, Yu. V.; Fedoseenko, A. M.; Yakovleva, S. Z.

2012-01-01

148

Experimental study of boundary layer transition on a heated flat plate  

Microsoft Academic Search

A detailed investigation to the document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were done in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft\\/s

K. H. Sohn; E. Reshotko; K. B. M. Q. Zaman

1991-01-01

149

Experimental study of boundary layer transition with elevated freestream turbulence on a heated flat plate  

Microsoft Academic Search

A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft\\/s and

Ki-Hyeon Sohn; Eli Reshotko

1991-01-01

150

A study in transitional flat plate boundary layers: measurement and visualization  

Microsoft Academic Search

This study is concerned with transition in flat plate boundary layer flow. Sets of results are obtained as follows: (1) Very\\u000a clear pictures of the formation and the development of the butterfly-like structures rather than ?-structures in the K-regime of boundary layer transition are obtained. (2) A chain of ring like vortices, which generate the high-frequency spikes\\u000a on the time

C. B. Lee; Z. X. Hong; Y. S. Kachanov; V. I. Borodulin; V. V. Gaponenko

2000-01-01

151

Tectonics and plate boundary processes along the Southeast Indian Ridge and the East Pacific Rise  

NASA Astrophysics Data System (ADS)

Classical plate tectonics describes crustal deformation in a simple kinematic way, with deformation occurring only at narrow boundaries of plates with rigid interiors. Many dynamic processes at these boundaries are not well understood. There are also apparent deviations from classical plate tectonics where significant intraplate deformation occurs. In this thesis, we analyze and model geophysical data from the Southeast Indian Ridge (SEIR) and the East Pacific Rise (EPR) to address some of these issues. Hotspots often affect the dynamics of nearby spreading centers. As shown by bathymetry, side-scan sonar, and magnetic anomaly data, the Amsterdam-St. Paul (ASP) hotspot has altered the spreading history and geometry of nearby SEIR spreading axes. The hotspot thickened the oceanic crust near the spreading center and reorganized the plate boundary through rift propagation and ridge jumps, creating the youngest known transform fault in the process. The region near the ASP plateau has been suggested as where a wide, diffuse, NW-SE trending oceanic plate boundary meets the SEIR. Using data from the SEIR, we perform a statistical analysis and examine predictions of the model to test its validity. The boundary is not confirmed on statistical grounds, but evidence suggests that it does exist. However, it does not extend south of the St. Paul Fracture Zone, narrowing the previously proposed boundary by 800 km where it meets the SEIR. We also test the hypothesis that deformation near the eastern end of the SEIR, including a large intraplate earthquake can be explained by an additional plate boundary. If the earthquake lies on a plate boundary, its sense of slip should be right-lateral rather than the observed left-lateral motion, ruling out the hypothesis. Asymmetric geophysical properties of the EPR near 17°S suggest more melt beneath the Pacific side than the Nazca side. Numerical modeling results indicate that the asymmetry may be produced by pressure-driven across-axis mantle flow from the Pacific superswell. Across-axis flow extends upwelling and melting to the west of the axis, but limits upwelling to the east, shutting off melting and accounting for the observed asymmetry.

Conder, James Andrew

152

Upper boundary of the Pacific plate subducting beneath Hokkaido, Japan, estimated from ScSp phase  

NASA Astrophysics Data System (ADS)

Three-dimensional geometry of the upper boundary of the Pacific plate subducting beneath Hokkaido, Japan, was obtained using the ScSp phase: the phase converted from ScS (S wave reflected at the core-mantle boundary) to P wave at the plate boundary. Taking the advantage of a dense seismic network, "Hi-net", recently deployed across the Japanese islands, we applied several seismic array analyses to the recorded waveform data for a large nearby deep earthquake, in order to enhance very weak ScSp signals in the original records. At first, we set up five blocks for the region in plate dip directions. After aligning the travel times of ScS and stacking seismograms among stations in a given sub-block perpendicular to each dip direction, we searched for the optimal plate model (i.e., two-dimensional geometry of the upper boundary) for each block. The model was parameterized by seven depth grids, and seismograms were stacked based on the travel time of ScSp as a time lag of each sub-block, so that the optimal model would yield the maximum spectral energy of ScSp after stacking. This model parameter search was conducted, using ray tracings of ScSp with a reference velocity model and a non-linear inversion scheme (Neighbourhood Algorithm). The optimal model of each block was combined each other by cubic spline interpolation, in order to construct an overall three-dimensional geometry of the upper boundary of the plate. Next, we performed the frequency-wavenumber ( f- k) spectral analysis to refine the above result. Assuming each station as a reference point, we made beam output from records of its adjacent stations as a function of wavenumber vector ( kx, ky) and frequency. The peak of its power spectrum was considered to represent the wavenumber vector of ScSp, that is, azimuth of arrival and slowness, so that we can estimate the position and depth of the corresponding ScS- ScSp conversion. In the frequency range from 0.5 to 1.5 Hz, we could estimate the conversion points for 21 stations or hypothetical arrays, and revised the geometry of the upper boundary obtained by the non-linear stacking approach in the previous step. The final plate model was compared with the distribution of intraplate earthquakes in the Pacific plate. This comparison clearly reveals that the upper seismic zone merges with the lower from 150 to 200 km in depth, deviating systematically away from the upper boundary where the boundary is slightly bumped in a convex manner.

Osada, Kinue; Yoshizawa, Kazunori; Yomogida, Kiyoshi; Suetsugu, Daisuke; Bina, Craig; Inoue, Toru; Wiens, Douglas; Jellinek, Mark

2010-11-01

153

Simulating the San Andreas Plate Boundary System: Progress and Prospects  

NASA Astrophysics Data System (ADS)

Computing the hazard posed by the next large earthquake on the San Andreas fault is best carried out with a simulation-based approach. Here we discuss a numerical simulation, Virtual California, that includes many of the physical processes known to be important in earthquake dynamics. These include elastic interactions among the faults in the model, driving at the correct plate tectonic rates, and frictional physics on the faults using the physics obtained from laboratory models with parameters consistent with the occurrence of historic earthquakes. We report progress on a variety of problems relating to the construction and use of increasingly realistic models for earthquakes on the San Andreas fault system, which will be required as the Working Group on California Earthquake Probabilities moves into its next phase of hazard and risk analysis. One of the important issues is to construct a fault system model based upon current WGCEP data. Here we use Deformation Model 2.2 ( http://www.relm.org/models/WGCEP/ ) to produce the most realistic model to date. We also have more fine-scale versions of previous models, including one model having 3 x 2**12 fault elements. While previous versions of Virtual California used only vertical strike slip faults, we are now incorporating dipping rectangular faults having arbitrary rake anble into the model as well. Versions of the basic code are available in Fortran, C, and object-oriented C++. One of the issues that we have encountered is the existence of a dynamical instability that arises as a direct result of the basic interactions between the fault elements, combined with the requirement that the long term slip rate on all fault elements match the observed field-derived average. Using these new models and simulations, we are engaged in novel types of data assimilation, using a method of "scoring" the simulation in comparison to observed paleoseismic data. In this paper, we summarize these results and discuss the implications for numerical forecasting methods

Rundle, P. B.; Rundle, J. B.; Yakovlev, G.; Fernandez, J.; Shcherbakov, R.; Turcotte, D. L.; Donnellan, A.; Field, N.; Grant, L.; Tiampo, K. F.; van Aalsburg, J.; Kellogg, L. H.

2006-12-01

154

India and Sunda plates motion and deformation along their boundary in Myanmar determined by GPS  

E-print Network

India and Sunda plates motion and deformation along their boundary in Myanmar determined by GPS with respect to mainland India. Including these points, using a longer time span than previous studies-day Indian motion. Our results confirm that the current motion of India is slower than predicted by the NUVEL

Socquet, Anne

155

Completion of the 16 station Plate Boundary Observatory (PBO) network on Mt. St. Helens, WA  

Microsoft Academic Search

The Plate Boundary Observatory (PBO), part of the larger NSF-funded EarthScope project, is completing year 3 of the installation phase of 852 continuously operating GPS stations in the Western United States. Some of these GPS stations are focused specifically on centers of volcanic activity. Mt. St. Helens is one of these volcanic areas of interest in the Pacific Northwest (PNW)

K. Austin; K. Hafner; K. Fengler; S. Doelger

2006-01-01

156

Upper mantle structure beneath the Caribbean-South American plate boundary from surface wave tomography  

E-print Network

by analysis of fundamental mode Rayleigh waves in the 20- to 100-s period band recorded at the BOLIVARUpper mantle structure beneath the Caribbean-South American plate boundary from surface wave 23 June 2008; accepted 9 October 2008; published 24 January 2009. [1] We have measured shear wave

Niu, Fenglin

157

Transition of compressible high enthalpy boundary layer flow over a flat plate  

Microsoft Academic Search

This paper presents the results of an experimental investigation of boundary layer transition to turbulence in hypervelocity flows. A preliminary series of experiments was conducted using a flat plate model equipped with static pressure and thin film heat transfer transducers in a free piston shock tunnel. In the laminar regions of the flow, the heat transfer was found to agree

Y. He; R. G. Morgan

1989-01-01

158

Experimental studies on the flat plate boundary layer transition using hydrogen bubble method  

Microsoft Academic Search

The transition from laminar flow to turbulent flow in the flat plate boundary layer was studied. The flow pattern was visualized using the hydrogen bubble method and the velocity variable waveforms were measured using a heated wire flowmeter. Using the test results of the visualized flow pattern and velocity variable waveforms, the following three phenomena were analyzed: (1) the Tollmien-Schlichting

Tatsuya Matsui; Muneshige Okude; Noriyasu Ishida

1990-01-01

159

Experimental investigation of boundary layer transition on a flat plate with C4 leading edge  

Microsoft Academic Search

This paper considers the effects of freestream turbulence intensity on the boundary layer transition over a range of Reynolds numbers. Bypass mode of transition has been considered using a flat plate with a C4 leading edge, designed to avoid laminar separation. This configuration provides the opportunity to study the effect of a realistic turbomachinery leading edge shape on transition. Hot

A. I. Kalfas; R. L. Elder

1993-01-01

160

Scaling Analysis of the Thermal Boundary Layer Adjacent to an Abruptly Heated Inclined Flat Plate  

Microsoft Academic Search

The natural convection thermal boundary layer adjacent to an abruptly heated inclined flat plate is investigated through a scaling analysis and verified by numerical simulations. In general, the development of the thermal flow can be characterized by three distinct stages, i.e. a start-up stage, a transitional stage and a steady state stage. Major scales including the flow velocity, flow development

S. C. Saha; C. Lei; J. C. Patterson

161

Hypocenter distribution of plate boundary zone off Fukushima Japan derived from ocean bottom seismometer data  

Microsoft Academic Search

Microearthquake observation using Ocean Bottom Seismometers (OBSs) was carried out to obtain a detailed distribution of microearthquakes beneath the area off Fukushima, in the middle section of the Japan Trench in the summer of 1997. The observation period spanned approximately one month. Almost all of the well-determined hypocenters occurred in the vicinity of the plate boundary in this region (approximately

Masanao Shinohara; Ryota Hino; Takashi Yoshizawa; Minoru Nishino; Kiyoshi Suyehiro

2005-01-01

162

The Azores-Gibraltar plate boundary: Focal mechanisms, depths of earthquakes, and their tectonic implications  

Microsoft Academic Search

We have analyzed the focal mechanisms and depths of 10 moderately sized earthquakes along the Azores-Gibraltar plate boundary by a variety of methods including formal inversion of the waveform and amplitude of teleseismic P and SH waves, first motion readings, and the identification of depth phases. Our data, together with a compilation of results reported for very large events from

Nina L. Grimison; Wang-Ping Chen

1986-01-01

163

Abrupt thermal transition reveals hydrothermal boundary and role of seamounts within the Cocos Plate  

E-print Network

associated with differences in the distribution of basement outcrops than with tectonic boundaries and the magnitude of earthquakes, the extent of diagenesis during subduction, and the structure and hydrogeology seaward of the Middle America Trench (MAT; Figure 1). The Cocos Plate has a complex tectonic history

Fisher, Andrew

164

Seismotectonics of plate boundaries. Final report, 1 November 1973-30 June 1981  

SciTech Connect

Research on the seismotectonics of plate boundaries is summarized. Instrumental development and an observational program designed to study various aspects of the seismotectonics of southern California and the northern Gulf of California are described. A unique superconducting gravimeter was further developed and supported under this program for deployment and operation at several sites. Work on Earth tides is also discussed.

Berger, J.; Brune, J.N.; Goodkind, J.; Wyatt, F.; Agnew, D.C.; Beaumont, C.

1981-06-01

165

The EarthScope Plate Boundary Observatory Response to the 2006 Augustine Alaskan Volcanic Eruption  

Microsoft Academic Search

During September of 2006, UNAVCO installed five permanent Plate Boundary Observatory (PBO) GPS stations on Augustine Volcano, in the lower Cook Inlet of Alaska. The installations were done at the request of the PBO Magmatic Systems committee in response to the January 11, 2006 eruption of Augustine Volcano. Prior to the eruption, PBO installed five permanent GPS stations on Augustine

B. Pauk; K. Feaux; M. Jackson; B. Friesen; M. Enders; A. Baldwin; K. Fournier; A. Marzulla

2006-01-01

166

Low heat flow inferred from .4 Gyr zircons suggests Hadean plate boundary interactions  

E-print Network

LETTERS Low heat flow inferred from .4 Gyr zircons suggests Hadean plate boundary interactions (the `Hadean' eon) remain poorly understood, largely because there is no rock record dating from that era. Detrital Hadean igneous zircons from the Jack Hills1 , Western Australia, however, can

Manning, Craig

167

The role of positive boundary data in the clamped plate equation, perturbation results and other generalizations  

E-print Network

solutions u 0. Here Rn is the "shape of the plate" (physically relevant for n = 2), is the exterior unit normal at , f is the (perpendicular) load, and are the boundary data and u is the deflection to lower order terms of the differential operator and in [GS2] with respect to the domain and the highest

Sweers, Guido

168

Discovering plate boundaries: Laboratory and classroom exercises using geodetic data to develop students' understanding of plate motion  

NASA Astrophysics Data System (ADS)

To introduce the concept of plate boundaries, typical introductory geology exercises include students observing and plotting the location of earthquakes and volcanoes on a map to visually demarcate plate boundaries. Accompanying these exercises, students are often exposed to animations depicting the movement of Earth’s tectonic plates over time. Both of these teaching techniques are very useful for describing where the tectonics plates have been in the past, their shapes, and where the plates are now. With the integration of data from current geodetic techniques such as GPS, InSAR, LiDAR, students can learn that not only have the tectonic plates moved in the past, but they are moving, deforming, and changing shape right now. Additionally, GPS data can be visualized using time scales of days to weeks and on the scale of millimeters to centimeters per year. The familiar temporal and spatial scales of GPS data also help students understand that plate tectonics is a process that is happening in the present and can ease the transition to thinking about processes that are typically described using deep time, a very difficult concept for students to grasp. To provide a more robust learning environment, UNAVCO has been incorporating high-precision GPS data into free, place-based, data-rich learning modules for educators and students in introductory Earth science courses at secondary and undergraduate levels. These modules integrate new scientific discoveries related to crustal deformation and explore applications of GPS, LiDAR, and InSAR techniques to research. They also provide students with case studies highlighting the process of scientific discovery, providing context and meaning. Concurrent to these efforts, tools to visualize the inter-relationships of geophysical and geologic processes, structures, and measurements including high-precision GPS velocity data are an essential part of the learning materials. Among the suite of visualization tools that UNAVCO has made available, the Jules Verne Voyager (JVV) interactive map tools are available online and are very well received by educators in introductory Earth science courses. In response to requests for easily accessible and usable data, UNAVCO built the Data for Educators webpage, incorporating an embedded Google Map with GPS locations and providing current GPS time series plots and downloadable data from the Plate Boundary Observatory. To extend and update the datasets available to our community, UNAVCO has developed a GPS velocity viewer using Google Maps technology and provides a learning- focused KMZ combining geophysical data sets for Google-Earth. By combining near real-time geodetic data with modern visualization tools into inquiry-based learning resources, students are deepening their understanding about the active nature of plate margins and gain a solid foundation for learning future concepts. UNAVCO is a non-profit, membership-governed consortium funded by the National Science Foundation and NASA.

Olds, S. E.

2010-12-01

169

Accretionary margin of north-western Hispaniola: morphology, structure and development of part of the northern Caribbean plate boundary  

USGS Publications Warehouse

Broad-range side-scan sonar (GLORIA) images and single- and multi-channel seismic reflection profiles demonstrate that the margin of north-western Hispaniola has experienced compression as a consequence of oblique North American-Caribbean plate convergence. Two principal morphological or structural types of accretionary wedges are observed along this margin. The first type is characterized by a gently sloping (???4??) sea floor and generally margin-parallel linear sets of sea-floor ridges that gradually deepen towards the flat Hispaniola Basin floor to the north. The ridges are caused by an internal structure consisting of broad anticlines bounded by thrust faults that dip southwards beneath Hispaniola. Anticlines form at the base of the slope and are eventually sheared and underthrust beneath the slope. In contrast, the second type of accretionary wedge exhibits a steeper (???6-16??) sea-floor slope characterized by local slumping and a more abrupt morphological transition to the adjacent basin. The internal structure appears chaotic on seismic reflection profiles and probably consists of tight folds and closely spaced faults. We suggest that changes in sea-floor declivity and internal structure may result from variations in the dip or frictional resistance of the de??collement, or possibly from changes in the cohesive strength of the wedge sediments. The observed pattern of thickening of Hispaniola Basin turbidites towards the insular margin suggests differential southwards tilting of the Hispaniola Basin strata, probably in response to North America-Caribbean plate interactions since the Early Tertiary. Based upon indirect age control from adjacent parts of the northern caribbean plate boundary, we infer a Late Eocene to Early Miocene episode of transcurrent motion (i.e. little or no tilting), an Early Miocene to Late Pliocene period of oblique convergence (i.e. increased tilt) during which the accretionary wedge began to be constructed, and a Late Pliocene to Recent episode of increased convergence (i.e. twice the Miocene to Pliocene tilt), which has led to rapid uplift and erosion of sediment sources on the margin and on Hispaniola, generating a submarine fan at the base of the insular slope. ?? 1992.

Dillon, W.P.; Austin, J.A., Jr.; Scanlon, K.M.; Terence, Edgar N.; Parson, L.M.

1992-01-01

170

Boundary layer flow and heat transfer past a moving plate with suction and injection  

NASA Astrophysics Data System (ADS)

The behavior of an incompressible steady boundary layer flow past a permeable semi-infinite flat plate moving in a free stream is discussed in this paper. In addition to the mass transfer from the plate (suction or injection), the viscous dissipation term is also included into the energy equation. The solutions of the transformed ordinary differential equations are obtained numerically using an implicit finite-difference method. The numerical results are given for the velocity and temperature profiles as well as for the skin friction coefficient and the local Nusselt number for various values of the suction/injection parameter ?, ratio of the wall velocity to the free stream velocity parameter ?, Prandtl number Pr and Eckert number Ec. It is found that suction increases the heat transfer by decreasing the thermal boundary layer thickness and the reverse happens for injection. Furthermore, it is also found that the boundary layer equations have non-unique (dual) solutions in some cases.

Ishak, Anuar; Nazar, Roslinda; Pop, Ioan

2014-06-01

171

Measurements of strain at plate boundaries using space based geodetic techniques  

NASA Technical Reports Server (NTRS)

We have used the space based geodetic techniques of Satellite Laser Ranging (SLR) and VLBI to study strain along subduction and transform plate boundaries and have interpreted the results using a simple elastic dislocation model. Six stations located behind island arcs were analyzed as representative of subduction zones while 13 sites located on either side of the San Andreas fault were used for the transcurrent zones. The length deformation scale was then calculated for both tectonic margins by fitting the relative strain to an exponentially decreasing function of distance from the plate boundary. Results show that space-based data for the transcurrent boundary along the San Andreas fault help to define better the deformation length scale in the area while fitting nicely the elastic half-space earth model. For subduction type bonndaries the analysis indicates that there is no single scale length which uniquely describes the deformation. This is mainly due to the difference in subduction characteristics for the different areas.

Robaudo, Stefano; Harrison, Christopher G. A.

1993-01-01

172

Late Cenozoic partitioning of oblique plate convergence in the Zagros fold-and-thrust belt (Iran)  

Microsoft Academic Search

The NW trending Zagros fold-and-thrust belt is affected by two major dextral faults: (1) the NW trending Main Recent Fault that accommodates partitioning of oblique convergence at the rear of the western Zagros and (2) the north trending Kazerun Fault located in the central Zagros. Combined structural and fault kinematics studies and SPOT images analysis have shown a Pliocene kinematic

Christine Authemayou; Dominique Chardon; Olivier Bellier; Zaman Malekzadeh; Esmaeil Shabanian; Mohammad Reza Abbassi

2006-01-01

173

New Constraints On The Caribbean-South America Plate Boundary From S Wave Receiver Functions  

NASA Astrophysics Data System (ADS)

BOLIVAR (Broadband Ocean-Land Investigation of Venezuela and the Antilles arc Region) was aimed at investigating the interplay between the lithospheric and asthenospheric mantle of the Caribbean and South America plates. We estimate lithospheric thickness from application of the S wave receiver function technique. This reveals lithospheric thinning from 95-105 km depth underneath the Guyana Shield in southern Venezuela to 60-75 km underneath the Caribbean Sea. We observe a comparable thinning on the passive margin transition in eastern Venezuela. Towards the west, the lithosphere-asthenosphere boundary (LAB) shallows to 80 km depth along a NE-SW trending structure bordering the Venezuelan Andes. In addition, the base of the lithosphere beneath the Maracaibo block in NW Venezuela is seen gently dipping towards the southwest. The observed lithospheric structure is consistent with established strike-slip tectonics along the northern boundary of South America. However, we find no evidence for southward subduction of the Caribbean plate as previously suggested. Instead, the boundary is better viewed as the combined motion of three lithospheric blocks: (1) the Caribbean and associated subduction in the Antilles, (2) South America, and (3) the Maracaibo block. The relatively sharp discontinuity in LAB beneath northern Venezuela leads to the conclusion that the Caribbean-South America plate boundary is (1) a structure of lithospheric scale, and (2) a continuous strike-slip plate boundary extending from NE Colombia to Trinidad in NE Venezuela along the Oca-San Sebastian-El Pilar fault zone. This boundary is overprinted in the west by northward translation of the Maracaibo block over the Caribbean.

Landes, M.; Pavlis, G. L.

2008-12-01

174

Seismic evidence for sharp lithosphere-asthenosphere boundaries of oceanic plates.  

PubMed

The mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics, and thus the understanding of the processes at the lithosphere-asthenosphere boundary (LAB) is fundamental to understand how our planet works. It is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the LAB. Data from borehole broadband ocean bottom seismometers show that the LAB beneath the Pacific and Philippine Sea plates is sharp and age-dependent. The observed large shear wave velocity reduction at the LAB requires a partially molten asthenosphere consisting of horizontal melt-rich layers embedded in meltless mantle, which accounts for the large viscosity contrast at the LAB that facilitates horizontal plate motions. PMID:19390042

Kawakatsu, Hitoshi; Kumar, Prakash; Takei, Yasuko; Shinohara, Masanao; Kanazawa, Toshihiko; Araki, Eiichiro; Suyehiro, Kiyoshi

2009-04-24

175

Discovering Plate Boundaries Update: Builds Content Knowledge and Models Inquiry-based Learning  

NASA Astrophysics Data System (ADS)

Discovering Plate Boundaries (DPB) is a jigsaw-structured classroom exercise in which students explore the fundamental datasets from which plate boundary processes were discovered. The exercise has been widely used in the past ten years as a classroom activity for students in fifth grade through high school, and for Earth Science major and general education courses in college. Perhaps more importantly, the exercise has been used extensively for professional development of in-service and pre-service K-12 science teachers, where it simultaneously builds content knowledge in plate boundary processes (including natural hazards), models an effective data-rich, inquiry-based pedagogy, and provides a set of lesson plans and materials which teachers can port directly into their own classroom (see Pringle, et al, this session for a specific example). DPB is based on 4 “specialty” data maps, 1) earthquake locations, 2) modern volcanic activity, 3) seafloor age, and 4) topography and bathymetry, plus a fifth map of (undifferentiated) plate boundary locations. The jigsaw is structured so that students are first split into one of the four “specialties,” then re-arranged into groups with each of the four specialties to describe the boundaries of a particular plate. We have taken the original DPB materials, used the latest digital data sets to update all the basic maps, and expanded the opportunities for further student and teacher learning. The earthquake maps now cover the recent period including the deadly Banda Aceh event. The topography/bathymetry map now has global coverage and uses ice-free elevations, which can, for example, extend to further inquiry about mantle viscosity and loading processes (why are significant portions of the bedrock surface of Greenland and Antarctica below sea level?). The volcanic activity map now differentiates volcano type and primary volcanic lithology, allowing a more elaborate understanding of volcanism at different plate boundaries. The volcanic activity map also now includes seafloor hydrothermal vents to extend the volcanic data set into the oceans. The new maps also more completely represent the polar regions, improving, for example, the students understanding of the ridge system running across the Arctic Sea. We have expanded the teacher’s guide to assist both novice and experienced teachers “see what an Earth Scientist sees” in the data. We have found repeatedly that the real strengths of the DPB activity are that (1) the course materials readily adapt to as well as appropriately challenge all levels of student abilities, leading to very natural differentiated levels of instruction, and (2) students of all levels develop a real ownership in their “plate tectonic” expertise.

Sawyer, D. S.; Pringle, M. S.; Henning, A. T.

2009-12-01

176

Inception of the eastern California shear zone and evolution of the PacificNorth American plate boundary: From kinematics  

E-print Network

] The San Andreas Fault (SAF) is the transform boundary between the Pacific and the North American plates American plates (Figure 1), the San Andreas Fault (SAF) proper accommodates 20%­75% of the relative plate proper, collectively referred to as the San Andreas Fault system [Wallace, 1990]. Furthermore, up to 25

Liu, Mian

177

Plate-Tectonic Analysis of Shallow Seismicity: Apparent Boundary Width, beta-Value, Corner Magnitude, Coupled Lithosphere Thickness, and Coupling in 7 Tectonic Settings  

NASA Astrophysics Data System (ADS)

A new plate model [Bird, 2003, G3, 10.1029/2001GC000252] is used to analyze the mean seismicities of 7 types of plate boundary (CRB continental rift boundary, CTF continental transform fault, CCB continental convergent boundary, OSR oceanic spreading ridge, OTF oceanic transform fault, OCB oceanic convergent boundary, SUB subduction zone). We compare the plate-like (non-orogen) regions of model PB2002 with the CMT catalog to select apparent boundary half-widths, and then assign 95% of shallow earthquakes to one of these settings. A tapered Gutenberg-Richter model of the frequency/moment relation is fit to the subcatalog for each setting by maximum-likelihood. Best-fitting ? values range from 0.53 to 0.92, but all 95%-confidence ranges are consistent with a common value of 0.61-0.66. To better determine some corner magnitudes we expand the subcatalogs by: (1) inclusion of orogens; and (2) inclusion of years 1900-1975 from the catalog of Pacheco and Sykes [1992]. Combining both earthquake statistics and the plate-tectonic constraint on moment rate, corner magnitudes include: CRB 7.64-.26+.76, CTF 8.01-.21+.45, CCB 8.46-.39+.21, OCB 8.04-.22+.52, and SUB 9.58-.46+.48. Coupled lithosphere thicknesses are found to be: CRB 3.0-1.4+7.0 km; CTF 8.6-4.1+11 km; CCB 18-11+? km; OSR 0.13-0.09+.13 km for normal-faulting and 0.40-.21+? km for strike-slip; OTF 12-7.1+?, 1.6-0.5+1.4, and 1.5-0.6+1.2 km at low, medium, and high velocities; OCB 3.8-2.3+13.7 km, and SUB 18.0-10.8+? km. Generally high coupling of subduction and continental plate boundaries suggests that here all seismic gaps are dangerous unless proven to be creeping. Generally low coupling within oceanic lithosphere suggests a different model of isolated seismic asperities surrounded by large seismic gaps which may be permanent.

Bird, P.; Kagan, Y. Y.

2003-12-01

178

Flow around a rotating circular cylinder with an end plate near a plane wall boundary  

NASA Astrophysics Data System (ADS)

The objective of the present study is to investigate the characteristics of a flow around a rotating circular cylinder with and without an end plate near a wall boundary. The different cases which are taken into consideration in the current investigations were with gap ratios of 0.1d, 0.5d, 1.0d, 1.5d and 2.0d. A symmetric end plate is attached behind the rotating circular cylinder at a distance of 0.1d from the cylinder and a gap ratio of 1.5d. We performed Computational Fluid Dynamics (CFD) simulation of the flow around a rotating circular cylinder near a plane wall boundary using a CFD solver, STAR-CCM+. Free-stream velocity is kept constant at 5 m/s and the Reynolds number calculated is 3.24X104. We then studied the flow characteristics such as lift and drag generated on the circular cylinder with and without an end plate and the wake structure. We observed that the vortex suppression is increased when the gap ratio is reduced, i.e., when the circular cylinder is nearer to the plane wall boundary. As the gap ratio increases the drag force generated decreases and the lift force increases considerably. In the case of rotating circular cylinder with an end plate, the wake area has moved upwards and the lift generated has increased manifold.

Panchal, Jay K.

179

Subcontinental-scale crustal velocity changes along the Pacific-North America plate boundary.  

PubMed

Transient tectonic deformation has long been noted within approximately 100 km of plate boundary fault zones and within active volcanic regions, but it is unknown whether transient motions also occur at larger scales within plates. Relatively localized transients are known to occur as both seismic and episodic aseismic events, and are generally ascribed to motions of magma bodies, aseismic creep on faults, or elastic or viscoelastic effects associated with earthquakes. However, triggering phenomena and systematic patterns of seismic strain release at subcontinental (approximately 1,000 km) scale along diffuse plate boundaries have long suggested that energy transfer occurs at larger scale. Such transfer appears to occur by the interaction of stresses induced by surface wave propagation and magma or groundwater in the crust, or from large-scale stress diffusion within the oceanic mantle in the decades following clusters of great earthquakes. Here we report geodetic evidence for a coherent, subcontinental-scale change in tectonic velocity along a diffuse approximately 1,000-km-wide deformation zone. Our observations are derived from continuous GPS (Global Positioning System) data collected over the past decade across the Basin and Range province, which absorbs approximately 25 per cent of Pacific-North America relative plate motion. The observed changes in site velocity define a sharp boundary near the centre of the province oriented roughly parallel to the north-northwest relative plate motion vector. We show that sites to the west of this boundary slowed relative to sites east of it by approximately 1 mm yr(-1) starting in late 1999. PMID:16810252

Davis, J L; Wernicke, B P; Bisnath, S; Niemi, N A; Elósegui, P

2006-06-29

180

Plate boundary forces in the vicinity of Trinidad-the-transition from transpression to transtension in the Southern Caribbean plate boundary zones  

SciTech Connect

Deformation in the southern Caribbean plate boundary zones as recorded in the Northern Range of Trinidad initiated in the Oligocene with northward vergent gravity sliding of Northern Range sediments due to uplift and oversteepening of the previously passive margin by the eastward migration of the Caribbean flexural forebulge. Progressive east-southeast transvergence of the Caribbean Plate with respect to South America overthrust incorporated the Northern Range sediments into the Caribbean accretionary prism, thrusting them south-southeast to produce a Middle Miocene transpressive foreland fold and thrust belt in southern Trinidad. Late Miocene deformation within Trinidad was increasingly dominated by right-lateral strike-slop (RLSS) faulting, at the expense of transpressive compressional features. Right-stepping of RLSS motion initiated the Gulf of Paria and Caroni pull-apart basins, Since Early Pliocene these basins and other areas to the north of Trinidad have undergone north-south extension in addition to east-west trending RLSS. Such extension caused the northward withdrawal of Caribbean terranes from atop of the Northern Range, Resulting in rapid isostatically induced uplift (approximately 0.5 mmyr[sup -1]). This change in deformation style may relate to a hitherto unrecognized shift in the relative motion of the eastern Caribbean Plate with respect to South America: from east-southeast-directed transpression to east-northeast-directed transtension.

Algar, S.T.; Pindell, J.L. (Dartmouth College, Hanover, NH (United States))

1993-02-01

181

A preliminary investigation of boundary-layer transition along a flat plate with adverse pressure gradient  

NASA Technical Reports Server (NTRS)

Boundary-layer surveys were made throughout the transition region along a smooth flat plate placed in an airstream of practically zero turbulence and with an adverse pressure gradient. The boundary-layer Reynolds number at the laminar separation point was varied from 1,800 to 2,600. The test data, when considered in the light of certain theoretical deductions, indicated that transition probably began with separation of the laminar boundary layer. The extent of the transition region, defined as the distance from a calculated laminar separation point to the position of the first fully developed turbulent boundary-layer profile, could be expressed as a constant Reynolds number run of approximately 70,000. Some speculations are presented concerning the application of the foregoing concepts, after certain assumptions have been made, to the problem of the connection between transition on the upper surface of an airfoil at high angles of attack and the maximum lift.

Von Doenhoff, Albert E

1938-01-01

182

MHD free convective boundary layer flow of a nanofluid past a flat vertical plate with Newtonian heating boundary condition.  

PubMed

Steady two dimensional MHD laminar free convective boundary layer flows of an electrically conducting Newtonian nanofluid over a solid stationary vertical plate in a quiescent fluid taking into account the Newtonian heating boundary condition is investigated numerically. A magnetic field can be used to control the motion of an electrically conducting fluid in micro/nano scale systems used for transportation of fluid. The transport equations along with the boundary conditions are first converted into dimensionless form and then using linear group of transformations, the similarity governing equations are developed. The transformed equations are solved numerically using the Runge-Kutta-Fehlberg fourth-fifth order method with shooting technique. The effects of different controlling parameters, namely, Lewis number, Prandtl number, buoyancy ratio, thermophoresis, Brownian motion, magnetic field and Newtonian heating on the flow and heat transfer are investigated. The numerical results for the dimensionless axial velocity, temperature and nanoparticle volume fraction as well as the reduced Nusselt and Sherwood number have been presented graphically and discussed. It is found that the rate of heat and mass transfer increase as Newtonian heating parameter increases. The dimensionless velocity and temperature distributions increase with the increase of Newtonian heating parameter. The results of the reduced heat transfer rate is compared for convective heating boundary condition and found an excellent agreement. PMID:23166688

Uddin, Mohammed J; Khan, Waqar A; Ismail, Ahmed I

2012-01-01

183

Convergence results for pseudospectral approximations of hyperbolic systems by a penalty type boundary treatment  

NASA Technical Reports Server (NTRS)

A new method of imposing boundary conditions in the pseudospectral approximation of hyperbolic systems of equations is proposed. It is suggested to collocate the equations, not only at the inner grid points, but also at the boundary points and use the boundary conditions as penalty terms. In the pseudo-spectral Legrendre method with the new boundary treatment, a stability analysis for the case of a constant coefficient hyperbolic system is presented and error estimates are derived.

Funaro, Daniele; Gottlieb, David

1989-01-01

184

The Theory of Plate Tectonics  

NSDL National Science Digital Library

This is a brief overview of the Theory of Plate Tectonics. According to the theory, the Earth's surface layer, or lithosphere, consists of seven large and 18 smaller plates that move and interact in various ways. Along their boundaries, they converge, diverge, and slip past one another, creating the Earth's seismic and volcanic activities. These plates lie atop a layer of partly molten rock called the asthenosphere. The plates can carry both continents and oceans, or exclusively one or the other. The site also explains interaction at the plate boundaries, which causes earthquakes, volcanoes and other forms of mountain building.

185

Tectonic plate under a localized boundary stress: fitting of a zero-range solvable model  

E-print Network

We suggest a method of fitting of a zero-range model of a tectonic plate under a boundary stress on the basis of comparison of the theoretical formulae for the corresponding eigenfunctions/eigenvalues with the results extraction under monitoring, in the remote zone, of non-random (regular) oscillations of the Earth with periods 0.2-6 hours, on the background seismic process, in case of low seismic activity. Observations of changes of the characteristics of the oscillations (frequency, amplitude and polarization) in course of time, together with the theoretical analysis of the fitted model, would enable us to localize the stressed zone on the boundary of the plate and estimate the risk of a powerful earthquake at the zone.

Petrova, L

2008-01-01

186

Tectonic plate under a localized boundary stress: fitting of a zero-range solvable model  

E-print Network

We suggest a method of fitting of a zero-range model of a tectonic plate under a boundary stress on the basis of comparison of the theoretical formulae for the corresponding eigenfunctions/eigenvalues with the results extraction under monitoring, in the remote zone, of non-random (regular) oscillations of the Earth with periods 0.2-6 hours, on the background seismic process, in case of low seismic activity. Observations of changes of the characteristics of the oscillations (frequency, amplitude and polarization) in course of time, together with the theoretical analysis of the fitted model, would enable us to localize the stressed zone on the boundary of the plate and estimate the risk of a powerful earthquake at the zone.

L. Petrova; B. Pavlov

2008-01-18

187

Tectonics of the Easter plate  

NASA Technical Reports Server (NTRS)

A new model for the Easter plate is presented in which rift propagation has resulted in the formation of a rigid plate between the propagating and dying ridges. The distribution of earthquakes, eleven new focal mechanisms, and existing bathymetric and magnetic data are used to describe the tectonics of this area. Both the Easter-Nazca and Easter-Pacific Euler poles are sufficiently close to the Easter plate to cause rapid changes in rates and directions of motion along the boundaries. The east and west boundaries are propagating and dying ridges; the southwest boundary is a slow-spreading ridge and the northern boundary is a complex zone of convergent and transform motion. The Easter plate may reflect the tectonics of rift propagation on a large scale, where rigid plate tectonics requires boundary reorientation. Simple schematic models to illustrate the general features and processes which occur at plates resulting from large-scale rift propagation are used.

Engeln, J. F.; Stein, S.

1984-01-01

188

Plate Borders and Mountain Building  

NSDL National Science Digital Library

This page features animations of four different types of plate boundaries, including one animation of the collision of two pieces of continental crust, forming steep mountain ranges. The animations are all presented in flash, and the plate convergence offers a useful, generic view of orogeny.

Schlumberger Excellence In Educational Development, Inc.

189

Gradual unlocking of plate boundary controlled initiation of the 2014 Iquique earthquake.  

PubMed

On 1 April 2014, Northern Chile was struck by a magnitude 8.1 earthquake following a protracted series of foreshocks. The Integrated Plate Boundary Observatory Chile monitored the entire sequence of events, providing unprecedented resolution of the build-up to the main event and its rupture evolution. Here we show that the Iquique earthquake broke a central fraction of the so-called northern Chile seismic gap, the last major segment of the South American plate boundary that had not ruptured in the past century. Since July 2013 three seismic clusters, each lasting a few weeks, hit this part of the plate boundary with earthquakes of increasing peak magnitudes. Starting with the second cluster, geodetic observations show surface displacements that can be associated with slip on the plate interface. These seismic clusters and their slip transients occupied a part of the plate interface that was transitional between a fully locked and a creeping portion. Leading up to this earthquake, the b value of the foreshocks gradually decreased during the years before the earthquake, reversing its trend a few days before the Iquique earthquake. The mainshock finally nucleated at the northern end of the foreshock area, which skirted a locked patch, and ruptured mainly downdip towards higher locking. Peak slip was attained immediately downdip of the foreshock region and at the margin of the locked patch. We conclude that gradual weakening of the central part of the seismic gap accentuated by the foreshock activity in a zone of intermediate seismic coupling was instrumental in causing final failure, distinguishing the Iquique earthquake from most great earthquakes. Finally, only one-third of the gap was broken and the remaining locked segments now pose a significant, increased seismic hazard with the potential to host an earthquake with a magnitude of >8.5. PMID:25119049

Schurr, Bernd; Asch, Günter; Hainzl, Sebastian; Bedford, Jonathan; Hoechner, Andreas; Palo, Mauro; Wang, Rongjiang; Moreno, Marcos; Bartsch, Mitja; Zhang, Yong; Oncken, Onno; Tilmann, Frederik; Dahm, Torsten; Victor, Pia; Barrientos, Sergio; Vilotte, Jean-Pierre

2014-08-21

190

Leading-edge receptivity of a hypersonic boundary layer on a flat plate  

Microsoft Academic Search

Experimental investigations of the boundary layer receptivity, on the sharp leading edge of a at plate, to acoustic waves induced by two-dimensional and three- dimensional perturbers, have been performed for a free-stream Mach number M[infty infinity] = 5.92. The fields of controlled free-stream disturbances were studied. It was shown that two-dimensional and three-dimensional perturbers radiate acoustic waves and that these

A. A. Maslov; A. N. Shiplyuk; A. A. Sidorenko; D. Arnal

2001-01-01

191

Coseismic slip resolution along a plate boundary megathrust: The Nankai Trough, southwest Japan  

Microsoft Academic Search

Geodetic survey measurements are used to estimate the coseismic slip distribution in the 1944 Tonankai (Mw=8.1) and 1946 Nankaido (Mw=8.3) earthquakes and to assess quantitatively the degree to which this slip is resolved on the plate boundary megathrust. Data used include 798 angle changes from triangulation surveys, 328 leveling section differences, and 5 coseismic tidal gage offsets. Many of the

Takeshi Sagiya; Wayne Thatcher

1999-01-01

192

Navier-Stokes simulations of the effects of suction holes on a flat plate boundary layer  

Microsoft Academic Search

Direct numerical simulations (DNS) of the Navier-Stokes equations are employed to explore the effects of suction holes on transition in a laminar flat plate boundary layer. The Navier-Stokes equations are cast in vorticity-velocity form. Periodicity is imposed in spanwise direction; all other spatial derivatives are discretized with fourth order compact differences. An explicit fourth order Runge-Kutta scheme is employed for

Hubert L. Meitz; Hermann F. Fasel

1994-01-01

193

Modeling of optimal perturbations in flat plate boundary layer using global modes: benefits and limits  

Microsoft Academic Search

The ability of capturing the noise amplifier dynamics of a boundary layer on a flat plate subjected to an adverse pressure\\u000a gradient by means of a global modes strategy is numerically investigated. After a brief description of the mechanism regarding\\u000a the exact optimal perturbation fields, the system is rewritten into an input–output framework. In order to achieve this, the\\u000a input

Frédéric Alizard; Jean-Christophe Robinet

2011-01-01

194

Transition of the boundary layer on a flat plate at supersonic and hypersonic velocities  

Microsoft Academic Search

The transition of the boundary layer from the laminar to the turbulent state on a smooth flat plate at a zero angle of attack\\u000a is studied in the range of Mach numbers M? = 2–6. It is demonstrated that the results measured at the end of the transition region can be approximated by a simple dependence\\u000a suitable for applications, which

V. I. Kornilov; SB RAS

2009-01-01

195

Polymer drag reduction with surface roughness in flat-plate turbulent boundary layer flow  

Microsoft Academic Search

Experimental results from a study of surface roughness effects on polymer drag reduction in a zero-pressure gradient flat-plate turbulent boundary layer are presented. Both slot-injected polymer and homogeneous polymer ocean cases were considered over a range of flow conditions and surface roughness. Balance measurements of skin friction drag reduction are presented. Drag reductions over 60% were measured for both the

H. L. Petrie; S. Deutsch; T. A. Brungart; A. A. Fontaine

2003-01-01

196

Plane wave diffraction by a finite plate with impedance boundary conditions.  

PubMed

In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in. PMID:24755624

Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

2014-01-01

197

Unsteady Boundary-Layer Flow over Jerked Plate Moving in a Free Stream of Viscoelastic Fluid  

PubMed Central

This study aims to investigate the unsteady boundary-layer flow of a viscoelastic non-Newtonian fluid over a flat surface. The plate is suddenly jerked to move with uniform velocity in a uniform stream of non-Newtonian fluid. Purely analytic solution to governing nonlinear equation is obtained. The solution is highly accurate and valid for all values of the dimensionless time 0 ? ? < ?. Flow properties of the viscoelastic fluid are discussed through graphs. PMID:24892060

Mehmood, Ahmer; Ali, Asif; Saleem, Najma

2014-01-01

198

Plane Wave Diffraction by a Finite Plate with Impedance Boundary Conditions  

PubMed Central

In this study we have examined a plane wave diffraction problem by a finite plate having different impedance boundaries. The Fourier transforms were used to reduce the governing problem into simultaneous Wiener-Hopf equations which are then solved using the standard Wiener-Hopf procedure. Afterwards the separated and interacted fields were developed asymptotically by using inverse Fourier transform and the modified stationary phase method. Detailed graphical analysis was also made for various physical parameters we were interested in. PMID:24755624

Nawaz, Rab; Ayub, Muhammad; Javaid, Akmal

2014-01-01

199

Lithospheric evolution of the Pacific–North American Plate Boundary considered in three dimensions  

Microsoft Academic Search

Tomographic images developed using the combined seismic networks of California and Nevada provide a three-dimensional view into Neogene Pacific–North American plate boundary evolution. Images reveal structures similar in size and spatial distribution to the large-scale structures observed at the surface. A prominent linear anomaly in the mantle is imaged beneath the western foothills to a depth of 70–90 km. Called the

Glenn P. Biasi

2009-01-01

200

Unsteady boundary-layer flow over jerked plate moving in a free stream of viscoelastic fluid.  

PubMed

This study aims to investigate the unsteady boundary-layer flow of a viscoelastic non-Newtonian fluid over a flat surface. The plate is suddenly jerked to move with uniform velocity in a uniform stream of non-Newtonian fluid. Purely analytic solution to governing nonlinear equation is obtained. The solution is highly accurate and valid for all values of the dimensionless time 0 ? ? < ?. Flow properties of the viscoelastic fluid are discussed through graphs. PMID:24892060

Munawar, Sufian; Mehmood, Ahmer; Ali, Asif; Saleem, Najma

2014-01-01

201

Preservation of contrasting geothermal gradients across the Caribbean-North America plate boundary (Motagua Fault, Guatemala)  

NASA Astrophysics Data System (ADS)

Strike-slip plate boundaries juxtapose crustal blocks that may have different geodynamic origins and therefore different thermal structures. Thermo-kinematic modeling of this type of strike-slip plate boundary predicts an asymmetric signature in the low-temperature thermochronologic record across the fault. Age-elevation profiles of zircon (U-Th)/He ages across the Motagua Fault, a 500 km long segment of the transform boundary between the North American and Caribbean plates, document a sharp cooling age discontinuity across the fault. This discontinuity could be interpreted as a difference in denudation history on each side of the fault. However, a low-relief Miocene erosional surface extends across the fault; this surface has been uplifted and incised and provides a geomorphic argument against differential denudation across the fault. By integrating magmatic, volcanic, and heat flow data, age-elevation profiles, and thermo-kinematic modeling, we propose that large horizontal displacement along the Motagua Fault has offset a persistent geothermal asymmetry across the fault and explains both the age discontinuities and the age-elevation patterns. This study illustrates how thermochronology can be used to detect large strike-slip displacements and more generally opens new perspectives in understanding the impact of nonuniform thermal structures on thermochronologic results.

Simon-Labric, Thibaud; Brocard, Gilles Y.; Teyssier, Christian; Beek, Peter A.; Fellin, Maria Giuditta; Reiners, Peter W.; Authemayou, Christine

2013-07-01

202

Plate boundary reorganization in the active Banda Arc-continent collision: Insights from new GPS measurements  

NASA Astrophysics Data System (ADS)

New GPS measurements reveal that large sections of the SE Asian Plate are progressively accreting to the edge of the Australian continent by distribution of strain away from the deformation front to forearc and backarc plate boundary segments. The study was designed to investigate relative motions across suspected plate boundary segments in the transition from subduction to collision. The oblique nature of the collision provides a way to quantify the spatial and temporal distribution of strain from the deformation front to the back arc. The 12 sites we measured from Bali to Timor included some from an earlier study and 7 additional stations, which extended the epoch of observation to ten years at many sites. The resulting GPS velocity field delineates at least three Sunda Arc-forearc regions around 500 km in strike-length that shows different amounts of coupling to the Australian Plate. Movement of these regions relative to SE Asia increases from 21% to 41% to 63% eastward toward the most advanced stages of collision. The regions are bounded by the deformation front to the south, the Flores-Wetar backarc thrust system to the north, and poorly defined structures on the sides. The suture zone between the NW Australian continental margin and the Sunda-Banda Arcs is still evolving with more than 20 mm/yr of movement measured across the Timor Trough deformation front between Timor and Australia.

Nugroho, Hendro; Harris, Ron; Lestariya, Amin W.; Maruf, Bilal

2009-12-01

203

In-Flight Boundary-Layer Transition on a Large Flat Plate at Supersonic Speeds  

NASA Technical Reports Server (NTRS)

A flight experiment was conducted to investigate the pressure distribution, local flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.0. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. The tests used a F-15B testbed aircraft with a bottom centerline mounted test fixture. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating for future laminar flow flight tests employing infrared thermography. Boundary-layer transition was captured using an onboard infrared imaging system. The infrared imagery was captured in both analog and digital formats. Surface pressures were measured with electronically scanned pressure modules connected to 60 surface-mounted pressure orifices. The local flow field was measured with five 5-hole conical probes mounted near the leading edge of the test fixture. Flow field measurements revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration. The infrared imaging system was able to capture shock wave impingement on the surface of the flat plate in addition to indicating laminar-to-turbulent boundary-layer transition.

Banks, Daniel W.; Fredericks, Michael Alan; Tracy, Richard R.; Matisheck, Jason R.; Vanecek, Neal D.

2012-01-01

204

Were the Great April 2012 Indian Ocean Earthquakes Triggered by the 2004 Plate Boundary Event?  

NASA Astrophysics Data System (ADS)

The Andaman-Sumatra subduction zone is the only plate boundary known to have generated two great strike-slip earthquakes following a great plate boundary earthquake. Thus, the 2004, Mw 9.2 thrust event and the Mw 8.6 and Mw 8.2 pair of earthquakes on 11 April, 2012 on the subducting oceanic plate form an intriguing sequence. The April events throw up some interesting questions. Could the twin earthquakes ~430 km from the Aceh coast of Northern Sumatra (~100 km away from the plate boundary) and at a depth of ~45 km be a consequence of the post-2004 visco-easltic processes and consequent changes in static stress? In a stress regime altered by a great plate boundary earthquake, can the pre-existing fractures be activated to generate great earthquakes? Based on our observations of the pre and post 2004 seismicity, we divide the subduction zone in to two segments- the northern Andaman segment (10-15 N) and the southern Nicobar segment (0-10 N). We focus more on the southern segment which features one of the most active oceanic plates in the world, being part of the diffused Indo-Australian plate boundary. The northern portion of this diffused plate boundary consists of the north-east or NNE trending linear feature known as the Ninety-east ridge. The 2012 sequence of great earthquakes occurred to the east of this ridge. The faulting mechanisms of these earthquakes remain debated. The Ninety-east ridge and paleo-transform faults that run parallel to the ridge justify the near N-S fault plane. Rupture models based on back projection of seismic data however suggests predominance of E-W faults, although they are not geomorphologically well expressed. The next important question is how these events are linked to the 2004 earthquake and how they are related to each other. We use the static stress change due to the 2004 event and alternate fault geometries to compute the static stress changes based on Coulomb's criterion, caused by the 2004 earthquake. Stress changes are computed for both the fault planes and at different depths (10km, 45km). Our studies suggest that the Mw 8.6 event occurred in a region of higher stress and one could argue that it was triggered by the stress changes that followed the 2004 earthquake. The subducting oceanic plate west of the Nicobar segment had actually been experiencing an increase in moment release after the 2004 earthquake. What triggered the Mw 8.2 soon after is another interesting question. Could it be similar to its predecessor, in response to the static stress changes caused by the 2004 event, but on a different fault? Or was it a static or dynamic response to the first earthquake?

M P, R.; Rajendran, K.

2013-12-01

205

Field fluctuations near a conducting plate and Casimir-Polder forces in the presence of boundary conditions  

E-print Network

We consider vacuum fluctuations of the quantum electromagnetic field in the presence of an infinite and perfectly conducting plate. We evaluate how the change of vacuum fluctuations due to the plate modifies the Casimir-Polder potential between two atoms placed near the plate. We use two different methods to evaluate the Casimir-Polder potential in the presence of the plate. They also give new insights on the role of boundary conditions in the Casimir-Polder interatomic potential, as well as indications for possible generalizations to more complicated boundary conditions.

S. Spagnolo; R. Passante; L. Rizzuto

2006-05-02

206

A fluvial record of plate-boundary deformation in the Olympics Mountains Trip Overview  

E-print Network

We have constructed a 2-day field trip designed to exhibit the geology, geomorphology, and active tectonics of the Pacific coast of the Olympic Peninsula. The trip is organized around the following three major topics that should generate lively discourse on how to use and interpret basic field relationships in tectonic geomorphology research: (1) What is a river terrace, how is it made, and what do river terraces tell us about active tectonics? (2) What is driving orogenesis for the Olympic Mountain segment of the Cascadia Subduction Zone? Is it shortening parallel to the direction of plate convergence, shortening normal to the direction of plate convergence, or some combination of both? Are there any geomorphic or stratigraphic field relationships that can actually be used to track the horizontal movement of rocks and thus interpret the shortening history over geologic time scales? (3) We know that uplift along Cascadia includes the effects of cyclic earthquake-related deformation, and long-term steady deformation. How do these different types of uplift influence incision and aggradation in the rivers of the Olympic Mountains?

Frank J. Pazzaglia; Mark T. Brandon; Karl W. Wegmann

207

Thrust -wrench interference tectonics in the Gulf of Cadiz (Africa -Iberia plate boundary in the North-East Atlantic): insights from  

E-print Network

Thrust - wrench interference tectonics in the Gulf of Cadiz (Africa - Iberia plate boundary to a segment of the Africa- Eurasia plate boundary previously described as tectonically diffuse (e.g. Sartori key segment of the Africa-Iberia plate boundary (North- East Atlantic ocean), three main different

Paris-Sud XI, Université de

208

Boundary layer flow of air over water on a flat plate  

NASA Technical Reports Server (NTRS)

A non-similar boundary layer theory for air blowing over a water layer on a flat plate is formulated and studied as a two-fluid problem in which the position of the interface is unknown. The problem is considered at large Reynolds number (based on x), away from the leading edge. A simple non-similar analytic solution of the problem is derived for which the interface height is proportional to x(sub 1/4) and the water and air flow satisfy the Blasius boundary layer equations, with a linear profile in the water and a Blasius profile in the air. Numerical studies of the initial value problem suggests that this asymptotic, non-similar air-water boundary layer solution is a global attractor for all initial conditions.

Nelson, John; Alving, Amy E.; Joseph, Daniel D.

1993-01-01

209

Boundary layer flow of air over water on a flat plate  

NASA Astrophysics Data System (ADS)

A non-similar boundary layer theory for air blowing over a water layer on a flat plate is formulated and studied as a two-fluid problem in which the position of the interface is unknown. The problem is considered at large Reynolds number (based on x), away from the leading edge. A simple non-similar analytic solution of the problem is derived for which the interface height is proportional to x(sub 1/4) and the water and air flow satisfy the Blasius boundary layer equations, with a linear profile in the water and a Blasius profile in the air. Numerical studies of the initial value problem suggests that this asymptotic, non-similar air-water boundary layer solution is a global attractor for all initial conditions.

Nelson, John; Alving, Amy E.; Joseph, Daniel D.

1993-08-01

210

A boundary element formulation for analysis of elastoplastic plates with geometrical nonlinearity  

NASA Astrophysics Data System (ADS)

In this paper a new boundary element method formulation for elastoplastic analysis of plates with geometrical nonlinearities is presented. The von Mises criterion with linear isotropic hardening is considered to evaluate the plastic zone. Large deflections are assumed but within the context of small strain. To derive the boundary integral equations the von Kármán’s hypothesis is taken into account. An initial stress field is applied to correct the true stresses according to the adopted criterion. Isoparametric linear elements are used to approximate the boundary unknown values while triangular internal cells with linear shape function are adopted to evaluate the domain value influences. The nonlinear system of equations is solved by using an implicit scheme together with the consistent tangent operator derived along the paper. Numerical examples are presented to demonstrate the accuracy and the validity of the proposed formulation.

Waidemam, Leandro; Venturini, Wilson Sergio

2010-03-01

211

Plate boundary deformation at the latitude of the Salton Trough - northern Gulf of California (Invited)  

NASA Astrophysics Data System (ADS)

Along the Pacific-North America plate boundary zone, the segment including the southern San Andreas fault to Salton Trough and northern Gulf of California basins has been transtensional throughout its evolution, based on Pacific-North America displacement vectors calculated from the global plate circuit (900 × 20 km at N54°W since 20 Ma; 460 × 20 km at N48°W since 11 Ma). Nevertheless, active seismicity and focal mechanisms show a broad zone of plate boundary deformation within which the inferred stress regime varies locally (Yang & Hauksson 2013 GJI), and fault patterns in some regions suggest ongoing tectonic rotation. Similar behavior is inferred to have occurred in this zone over most of its history. Crustal structure in this region is constrained by surface geology, geophysical experiments (e.g., the 2011 Salton Seismic Imaging Project (SSIP), USGS Imperial Valley 1979, PACE), and interdisciplinary marine and onland studies in Mexico (e.g., NARS-Baja, Cortes, and surveys by PEMEX). Magnetic data (e.g., EMAG-2) aids in the recognition of large-scale crustal provinces and fault boundaries in regions lacking detailed geophysical surveys. Consideration of existing constraints on crustal thickness and architecture, and fault and basin evolution suggests that to reconcile geological deformation with plate motion history, the following additional factors need to be taken into account. 1) Plate boundary displacement via interacting systems of rotating blocks, coeval with slip on steep strike slip faults, and possibly related to slip on low angle extensional faults (e.g, Axen & Fletcher 1998 IGR) may be typical prior to the onset of seafloor spreading. This fault style may have accommodated up to 150 km of plate motion in the Mexican Continental Borderland and north of the Vizcaino Peninsula, likely between 12 and 15 Ma, as well as explaining younger rotations adjacent to the Gulf of California and current deformation southwest of the Salton Sea. 2) Geophysical characteristics suggest that the zone of strike-slip faults related to past plate boundary deformation extends eastward into SW Arizona and beneath the Sonoran coastal plain. 3) 'New' crust and mantle lithosphere at the plate boundary, in the Salton Trough and the non-oceanic part of the northern Gulf of California, varies in seismic velocity structure and dimensions, both within and across extensional segments. Details of within-segment variations imaged by SSIP (e.g., Ma et al., and Han et al., this meeting) are attributed to active fault patterns and small scale variations in hydrothermal activity and magmatism superposed on a more uniform sedimentation. Differences between the Imperial Valley rift segment and the north Gulf of California segments may be due to more involvement of low angle normal faults in the marine basins in the south (Martin et al., 2013, Tectonics), as well as differences in lower crustal or mantle lithospheric flow from the adjacent continental regions.

Stock, J. M.

2013-12-01

212

High-order Galerkin convergence and boundary characteristics of the 3-D Navier-Stokes equations on intervals of regularity  

NASA Astrophysics Data System (ADS)

We consider the 3-D Navier-Stokes equations (NSE) on a bounded domain ??R with zero boundary data. Let P denote the Leray projection and let A=-P? denote the Stokes operator. For a natural number ??2 assume that the forcing data satisfies f?C([0,T],D(A)), and let [0,T] be an interval over which the H1-norms of Galerkin solutions um are uniformly bounded. Then on any subinterval [?,T] we show that supt?[?,T] ?A(um(t)-u(t))?2?0 as m?? where u is the unique regular strong solution of the NSE on [0,T]. From this convergence result we show that if f?C([0,T];D(A)) then Au(t)=0 on the boundary ? of ? for any t>0. When ?=2 applications of this boundary result include boundary data specification for the NSE pressure within the framework developed in [19,20], and corroboration for the choice of boundary values in [22] for the NS-? equation.

Avrin, Joel

2014-10-01

213

Seismotectonics of the Lwandle-Nubia plate boundary between South Africa and the Southwest Indian Ridge  

NASA Astrophysics Data System (ADS)

The Lwandle (LW) plate shares a boundary with the Nubia (NU) plate, extending from a diffuse triple junction with the Rovuma plate in Southern Mozambique to a triple junction with the Antarctic plate along a segment of the Southwest Indian Ridge (SWIR). The LW-NU boundary terminates in the ~750 km-long, complex transform of the Andrew Bain Fracture Zone (ABFZ), but its exact locus is still unclear. Recent works locate it along the eastern boundary of the submarine Mozambique Ridge, parallel to the pre-existing, oceanic transform-fault fabric. However, an early concept of the LW block ('ambiguous region' of Hartnady, 1990, Fig. 2) indicates a more westerly trajectory in the north that includes parts of South Africa, with a southerly extension across old oceanic crust of the submarine Natal Valley and Transkei Basin. This proposed boundary is marked by several, aligned epicentres of moderate to strong earthquakes (1941, 1942, 1956, 1969, 1972, 1975, 1981 and 1989). Our re-examination of seismographic records from the 1975 'intraplate' earthquake (-37.62°N, 30.98°E, mb5.0), in the oceanic crust of the distal Transkei Basin, shows a thrust-faulting focal mechanism along a nodal plane striking N272°E. The largest (ML4.2) of a series of three small earthquakes in the Natal Valley in 2009, close to a zone of recent seafloor deformation mapped in 1992, has similar first-motion patterns at Southern African seismograph stations. When the 1975 slip-vector result (N173°E) is combined with a normal-faulting slip vector (N078°E) from a 1986 onland earthquake (-30.53°N, 28.84°E, mb5.0) near the Lesotho-KZN border, and both are incorporated into the wider data-set previously used to solve for East African Rift kinematics, they produce a LW-NU rotation pole that is located south of Africa, near the Agulhas Plateau, and approximately 950 km from the Natal Valley deformation zone. The modeled low rate of right-lateral, LW-NU slip (~0.50-0.75 mm/yr) across this LW-NU boundary segment suggests that the 1972, 1981 and nearby 2009 earthquakes are instances of a 'long aftershock sequence' in the source zone of the 1850 'i-Nyikima' event, which was felt over a very wide region of the Eastern Cape Colony, and the adjacent territories of British Kaffraria and Pondoland. This remarkable historic shaking appears to have been caused by a great (Mw8.0+), oceanic event along a segment of the LW-NU boundary, resembling the 1942 SWIR event along the ABFZ and the recent (2012 March 11) North Indian Ocean events along the incipient boundary between the Indian and Australian plates. This new interpretation has implications for the re-assessment of seismic and submarine-landslide (tsunami) hazard along the SE continental margin of South Africa. Reference Hartnady CJH (1990). Seismicity and plate boundary evolution in southeastern Africa. S. Afr. J. Geol. 93, 473 484.

Hartnady, Chris; Okal, Emile; Calais, Eric; Stamps, Sarah; Saria, Elifuraha

2013-04-01

214

GPS and tectonic evidence for a diffuse plate boundary at the Azores Triple Junction  

NASA Astrophysics Data System (ADS)

We use GPS, bathymetric/structural, and seismic data to define the pattern of present deformation along the northern half of the Azores plateau, where the Nubia-Eurasia plate boundary terminates at the axis of the Mid-Atlantic Ridge (MAR). New and existing campaign GPS velocities from the Azores islands reveal extension oblique to a series of en échelon volcanic ridges occupied by Terceira, S. Jorge, Pico, and Faial islands. In a frame of reference defined by 69 continuous GPS stations on the Eurasia plate, Terceira Island moves 2±1 mm/yr away from Eurasia, consistent with the island's location within the Terceira Rift and plate boundary structure. The volcanic ridges south of the Terceira Rift move toward WSW at progressively faster rates, reaching a maximum of 3.5±0.5 mm/yr (2-?) for the Pico/Faial volcanic ridge. The hypothesis that the Terceira Rift accommodates all Nubia-Eurasia plate motion is rejected at high confidence level based on the motions of sites on S. Jorge Island just west of Terceira Rift. All of the islands move relative to the Nubia plate, with Pico Island exhibiting the slowest motion, only 1±0.5 mm/yr (2-?). Detailed bathymetry from the interior of the hypothesized Azores microplate reveals faults that crosscut young MAR seafloor fabric. These observations and the GPS evidence for distributed deformation described above argue against the existence of a rigid or semi-rigid Azores microplate, and instead suggest that Nubia-Eurasia plate motion is accommodated by extension across a ˜140-km-wide zone east of the MAR axis, most likely bounded to the north by the northern shoulder of the Terceira Rift. The MAR spreading rate along the western end of the Azores deformation zone (˜38.5°N-39.5°N) is intermediate between the Eurasia-North America rate measured at 39.5°N and the Nubia-North America rate measured at 38.5°N, consistent with the joint conclusions that the Nubia-Eurasia boundary is broad where it intersects the MAR, and the Azores Triple Junction is diffuse rather than discrete.

Marques, F. O.; Catalão, J. C.; DeMets, C.; Costa, A. C. G.; Hildenbrand, A.

2013-11-01

215

The 2000 Mw 6.8 Uglegorsk earthquake and regional plate boundary deformation of Sakhalin from geodetic data  

Microsoft Academic Search

Interseismic GPS velocities in Sakhalin indicate that the island moves to the west at 3–4 mm\\/yr with respect to the Eurasian plate, which is about half of the relative Eurasia - North America plate convergence rate. GPS measurements across the central Sakhalin fault system provide evidence of compressive and strike-slip strain accumulation at a rate ?3 mm\\/yr. Coseismic vertical displacements

M. G. Kogan; R. Bürgmann; N. F. Vasilenko; C. H. Scholz; R. W. King; A. I. Ivashchenko; D. I. Frolov; G. M. Steblov; Ch. U. Kim; S. G. Egorov

2003-01-01

216

First epoch geodetic measurements with the Global Positioning System across the northern Caribbean plate boundary zone  

NASA Technical Reports Server (NTRS)

The first geodetic survey across the northern Caribbean plate boundary zone with GPS was conducted in June 1986. Baseline vectors defined by the six-station regional GPS network ranged from 170 to 1260 km in length. Repeatability of independent daily baseline estimates was better than 8 mm plus 1.3 parts in 10 to the 8th of baseline length for horizontal components. The wet tropospheric path delay during the experiment was both high, sometimes exceeding 30 cm at zenith, and variable, sometimes exceeding 5 cm variation over several hours. Successful carrier phase cycle ambiguity resolution (bias fixing) could not be achieved prior to construction of a regional troposphere model. With optimum troposphere treatment and single-day orbital arcs, most biases on baselines were resolved up to about 550 km in length. With multiday orbital arcs most biases in the network were resolved regardless of baseline length. The results suggest that constraints on plate-boundary zone deformation in the Greater Antilles, and on the North America-Caribbean relative plate motion vector, can be obtained with a series of GPS experiments spanning less than 10 and 15 years, respectively.

Dixon, T. H.; Gonzalez, G.; Lichten, S. M.; Katsigris, E.

1991-01-01

217

Implication of the Central Gulf of California (MX) Earthquake cycle in understanding continental plate boundary rheology  

NASA Astrophysics Data System (ADS)

The Gulf of California is characterized by the development of a highly oblique plate boundary that rifted the Baja California Peninsula from mainland North America through a series of long transform faults and deep basins. Within the central part of Gulf of California 90 % of the relative motion between North America and Pacific plate is localized in a very narrow region between the Baja California peninsula and a chain of islands (in particular Angel de la Guarda and San Lorenzo). In August 2009 and April 2012, two earthquakes (Mw~7) struck the region. The collection of campaign GPS data since 2004 and after the two seismic events, allows an evaluation of the surface deformation during the full earthquake cycle. Here we focus on the surface deformation relative to a rigid Baja California motion (defined by GPS observations along the Peninsula) during the interseismic period before the two seismic events, and the co- and post-seismic period of each earthquake. In particular, we explore the implications of the post-seismic surface deformation in understanding the rheological and mechanical properties underneath the seismogenic layer in a region characterized by a developing plate boundary. a) Interseismic velocity field in a Baja fixed reference frame. b-c) cosesimic displacement fro the 2009 and 2012 seismic events (focal mechanisms from Global CMT web page) Relative position with respect to the first observation of the two stations closest to the coast up to July 1st 2012.

Malservisi, R.; Plattner, C.; Hackl, M.; Suarez Vidal, F.

2012-12-01

218

Quasi-Love Surface Wave Observations on USArray: Evidence for Upper Mantle Anisotropy Along the North American Plate Boundary  

Microsoft Academic Search

Strong evidence for mantle anisotropy exists along the North American and Pacific plate boundary, likely a result of deformation of upper-mantle rocks from the applied stress of tectonic motion. We have observed anisotropy-sensitive Love-to-Rayleigh scattered waves, also known as Quasi-Love waves, on the USArray component of EarthScope, on propagation paths that cross the North American plate boundary. These observed Quasi-Love

D. M. Rieger

2008-01-01

219

Separation in the mixed convection boundary-layer radial flow over a constant temperature horizontal plate  

NASA Astrophysics Data System (ADS)

The boundary-layer flow of a horizontal current emerging radially from a cylindrical vertical surface of radius r0 with a constant velocity over a heated horizontal wall at constant temperature is analyzed. The boundary-layer equations are made dimensionless with a radial characteristic length in which natural and forced convection become of the same order of magnitude, so that the Prandtl (Pr) number and Gr2/Re5 are the only nondimensional parameters governing the problem, where Gr and Re are the Grashof and Reynolds numbers based on r0, respectively. A similarity solution valid at the leading edge of the boundary-layer flow is obtained. It contains, as the first order correction to Blasius' thermal boundary layer solution, the effect of buoyancy, and as the second order correction the effect of the radial divergence of the flow. This solution is used to start the numerical integration of the equations to provide a criterion for when separation occurs. It is found that separation, based on the boundary layer model, occurs for Gr < B(Pr)Re5/2, where the Prandtl's number function B is characterized numerically and found to be almost constant. This separation location law is compared with experimental results for air flowing over a heated horizontal plate at constant temperature, finding a qualitative good agreement.

Fernandez-Feria, R.; del Pino, C.; Fernández-Gutiérrez, A.

2014-10-01

220

Relaxation of an unsteady turbulent boundary layer on a flat plate in an expansion tube  

NASA Technical Reports Server (NTRS)

An analysis is presented for the relaxation of a turbulent boundary layer on a semi-infinite flat plate after passage of a shock wave and a trailing driver gas-driven gas interface. The problem has special application to expansion-tube flows. The flow-governing equations have been transformed into the Crocco variables, and a time-similar solution is presented in terms of the dimensionless distance-time variable alpha and the dimensionless velocity variable beta. An eddy-viscosity model, similar to that of time-steady boundary layers, is applied to the inner and outer regions of the boundary layer. A turbulent Prandtl number equal to the molecular Prandtl number is used to relate the turbulent heat flux to the eddy viscosity. The numerical results, obtained by using the Gauss-Seidel line-relaxation method, indicate that a fully turbulent boundary layer relaxes faster to the final steady-state values of heat transfer and skin friction than a laminar boundary layer. The results also give a fairly good estimate of the local skin friction and heat transfer for near steady-flow conditions.

Gurta, R. N.; Trimpi, R. L.

1974-01-01

221

Contraction along a previously extended plate boundary; analogue modelling of the Iberian - Eurasian suture zone  

NASA Astrophysics Data System (ADS)

The Iberian - Eurasian plate boundary can be roughly subdivided into a continent-continent and a continent-ocean collision zone in the east and west, respectively. This is due to the extensional phase that predates the contraction that formed the present day mountains in the area. A narrow ocean seaway separated the Iberian and Eurasian plates, whereas a wider ocean opened up towards west, where the present day Bay of Biscay lies. The deep seismic structures under the eastern segment show a subduction of the Iberian plate under the Eurasian plate, whereas the western segment is less well constrained and leave room for discussion regarding deep geometries and the nature of the collision zone. An analogue experiment was designed to represent the tectonic setting at the boundary at the culmination of the extensional phase in the early Cretaceous and then contracted to explore how surface topography and deep structures are affected by changes in upper mantle strength and contraction rate. The model is composed of layers of silicone putty and sand, tailored to simulate the assumed lithospheric geometries and strength-viscosity profiles along the plate boundary zone, and comprises two 'continental' plates separated by a thinner 'oceanic' plate that represents the narrow seaway that separated the eastern areas, and opens up to a 30° angle in the west, representing the Bay of Biscay. The experiment floats on a substrate of sodium polytungstate, representing mantle. The experiment was run 24 times, varying the thickness (and thus strength) of the upper mantle lithosphere, and the contraction rate. Keeping all other parameters identical for each experiment, the models were shortened by a computer-controlled jackscrew while time-lapse images were recorded. After completion, the models were saturated with water and frozen, allowing for sectioning and profile inspection. Of the 19 successful iterations of the experiment, three shortening rates were tested, each value representing an order of magnitude higher than the previous, and three thickness values (and thus strength) were applied to the sand layer representing upper mantle lithosphere. The results show how upper mantle strength appears to be the most important factor in determining whether an inversion of subduction direction occurs. A weak upper mantle layer (weaker than the oceanic crust) leads to obduction of the oceanic crust in the western segment of the model, forcing a significantly different scenario compared to observations in NW Spain today. In model iterations where the upper mantle is stronger than the oceanic crust, most model outcomes show a reversal in subduction polarity from northerly in the east, to southerly in the west. The transition zone is located where the narrow, parallel 'seaway' opens up towards west, near the centre of the model. Surface inspection of the models also show consistent patterns of faults breaking the surface, and are comparable to the present day major fault patterns mapped along the Pyrenean and Cantabrian mountains. It is concluded that both deep and surface structures are at least in part a result of the inherent zone of weakness that developed along the Iberian - Eurasian plate boundary.

Midtkandal, I.; Gabrielsen, R. H.; Brun, J.; Huismans, R. S.

2011-12-01

222

Paleoseismicity of the North American-Caribbean plate boundary (Septentrional fault), Dominican Republic  

USGS Publications Warehouse

The Septentrional fault zone, the major North American-Caribbean plate-boundary fault in Hispaniola, is a likely source of large earthquakes in the Dominican Republic. An excavation into a Holocene alluvial fan deposited across the fault in the central Cibao Valley, Dominican Republic, provides evidence that it has been at least 430 yr and probably more than 740 yr since the last ground-rupturing earthquake along this segment of the fault. On the basis of these data and published estimates of the plate-tectonic slip rate, it is proposed that the Septentrional fault is a source of high seismic potential in the densely populated and rapidly developing Cibao Valley in the northern Dominican Republic. -Authors

Prentice, C. S.; Mann, P.; Taylor, F. W.; Burr, G.; Valastro, S.

1993-01-01

223

Prehistoric earthquakes on the Caribbean-South American plate boundary, central range fault, Trinidad  

USGS Publications Warehouse

Recent geodetic studies suggest that the Central Range fault is the principal plate-boundary structure accommodating strike-slip motion between the Caribbean and South American plates. Our study shows that the fault forms a topographically prominent lineament in central Trinidad. Results from a paleoseismic investigation at a site where Holocene sediments have been deposited across the Central Range fault indicate that it ruptured the ground surface most recently between 2710 and 550 yr B.P. If the geodetic slip rate of 9-15 mm/yr is representative of Holocene slip rates, our paleoseismic data suggest that at least 4.9 m of potential slip may have accumulated on the fault and could be released during a future large earthquake (M > 7). ?? 2010 Geological Society of America.

Prentice, C. S.; Weber, J. C.; Crosby, C. J.; Ragona, D.

2010-01-01

224

Prehistoric earthquakes on the Caribbean-South American plate boundary, central Range Fault, Trinidad  

USGS Publications Warehouse

Recent geodetic studies suggest that the Central Range fault is the principal plate-boundary structure accommodating strike-slip motion between the Caribbean and South American plates. Our study shows that the fault forms a topographically prominent lineament in central Trinidad. Results from a paleoseismic investigation at a site where Holocene sediments have been deposited across the Central Range fault indicate that it ruptured the ground surface most recently between 2710 and 550 yr B.P. If the geodetic slip rate of 9–15 mm/yr is representative of Holocene slip rates, our paleoseismic data suggest that at least 4.9 m of potential slip may have accumulated on the fault and could be released during a future large earthquake (M > 7).

Carol S Prentice; Christopher J Crosby; Weber, John C.; Ragona, Daniel

2010-01-01

225

Linear stability analysis in compressible, flat-plate boundary-layers  

Microsoft Academic Search

The stability problem of two-dimensional compressible flat-plate boundary layers is handled using the linear stability theory.\\u000a The stability equations obtained from three-dimensional compressible Navier–Stokes equations are solved simultaneously with\\u000a two-dimensional mean flow equations, using an efficient shoot-search technique for adiabatic wall condition. In the analysis,\\u000a a wide range of Mach numbers extending well into the hypersonic range are considered for

Serkan Özgen; Senem Atalayer K?rcal?

2008-01-01

226

Group method analysis of unsteady free-convective laminar boundary-layer flow on a nonisothermal vertical flat plate  

Microsoft Academic Search

The transformation group theoretic approach is applied to present an analysis of the problem of unsteady laminar free convection from a nonisothermal vertical flat plate. The application of two-parameter groups reduces the number of independent variables by two, and consequently the system of governing PDEs with boundary conditions reduces to a system of ODEs with appropriate boundary conditions. The possible

M. B. Abd-El-Malek; Y. Z. Boutros; N. A. Badran

1990-01-01

227

Group theoretic approach for solving time-independent free-convective boundary layer flow on a nonisothermal vertical flat plate  

Microsoft Academic Search

A general procedure is presented for applying one-parametric group transformation to the set of governing partial differential equations and the boundary conditions in the problem of steady laminar free convection from a nonisothermal vertical flat plate. The transformation is used to reduce the partial differential equations to simultaneous ordinary differential equations with appropriate boundary conditions. The equations are then solved

Y. Z. Boutros; M. B. Abd-El-Malek; N. A. Badran

1990-01-01

228

A moving-wall boundary layer flow of a slightly rarefied gas free stream over a moving flat plate  

Microsoft Academic Search

In the current work, the boundary layer flow of a slightly rarefied gas free stream over a moving flat plate is presented and solved numerically. The first-order slip boundary condition is adopted in the derivation. The dimensionless velocity and shear stress profiles are plotted and discussed. A theoretical derivation of the estimated solution domain is developed, which will give a

Tiegang Fang; Chia-fon F. Lee

2005-01-01

229

Transition to turbulence in the boundary layer over a smooth and rough swept plate exposed to free-stream turbulence  

Microsoft Academic Search

Receptivity, disturbance growth and transition to turbulence of the three-dimensional boundary layer developing on a swept flat plate are studied by means of numerical sim- ulations. The flow is subject to a favorable pressure gradient and represents a model for swept-wing flow downstream of the leading edge and upstream of the pressure minimum of the wing. The boundary layer is

Lars-Uve Schrader; Subir Amin; Luca Brandt

2010-01-01

230

Natural convection boundary-layer adjacent to an inclined flat plate subject to sudden and ramp heating  

Microsoft Academic Search

The natural convection thermal boundary-layer adjacent to an inclined flat plate subject to sudden heating and a temperature boundary condition which follows a ramp function up until a specified time and then remains constant is investigated. The development of the flow from start-up to a steady state has been described based on scaling analyses and verified by numerical simulations. Different

Suvash C. Saha; John C. Patterson; Chengwang Lei

2010-01-01

231

Flow of a non-Newtonian fluids on a flat plate: I. boundary layer  

E-print Network

A modified power-law viscosity for non-Newtonian fluids based on actual measurements is proposed. This realistic model allows removal of the singularities at the leading edge of a flat-plate boundary-layer for either shear-thinning or shear-thickening fluids. Under this condition, the boundary-layer equations can be solved numerically by simple finite-difference methods that march downstream from the leading edge, as is usually done for Newtonian fluids. Nu-merical results are presented for the case of a shear-thinning fluid; applying the model to a shear-thickening fluid is straightforward. The effects of this new variable viscosity are explic-itly demonstrated by comparing plots of iso-lines of viscosity and shear-rate, the velocity dis-tribution, and the wall shear stress for non-Newtonian and Newtonian fluids.

Yao, Lun-Shin

2007-01-01

232

Singularities of the boundary layer equations and the structure of the flow in the vicinity of the convergence plane on conical bodies  

Microsoft Academic Search

The singularities of the boundary layer equations and the laminar viscous gas flow structure in the vicinity of the convergence\\u000a plane on sharp conical bodies at incidence are analyzed. In the outer part of the boundary layer the singularities are obtained\\u000a in explicit form. It is shown that in the vicinity of a singularity a boundary domain, in which the

V. I. Shalaev

2007-01-01

233

Using GPS, tide gauge and altimetry data to constrain subduction parameters at the Vanuatu plate boundary.  

NASA Astrophysics Data System (ADS)

The Vanuatu subduction zone, Southwest Pacific, combines several features that makes it a particularly useful place to study seismic cycles. The convergence rate is high - approximately 12 cm/yr - and the seismic cycle relatively short. Measurements of interseismic motions are helped by relatively high vertical rates, the close proximity of some islands to the plate interface and the existence of very shallow seamounts on either side of the plate interface. The Vanuatu archipelago is part of the Pacific Ring of Fire: the Australian plate subducts eastward beneath the North Fiji basin, on the western border of the Pacific Plate. High topographic features on the diving plate may contribute to locking of the plates, which can play a major role in the genesis of destructive earthquakes. GPS network points were installed in the early 1990s and the geodesy network has been densified through the years, enabling us to map interseismic horizontal and vertical deformation rates throughout the archipelago. More recently, 8 continuous GPS stations were installed, along with 3 continuous seafloor pressure gauges very near to the plate interface. We show results from GPS data collected from 1996 to 2011, that we re-processed and combined into the ITRF2008 reference frame, and altimetry and seafloor pressure data from 1999 to 2010. The GPS results show that vertical deformation rates vary both across and along the archipelago. We believe that these variations result from variable distance to the plate limit and variable locking parameters. In some areas, subsidence rates are close to one centimeter per year. In the Torres islands (at the northern end of the archipelago) where villagers face recurrent coastal flooding, we showed that this flooding is due more to ground motion than to rise in the absolute sea level, even though the sea-level rise rates are locally high and the islands uplift over the long term. In the Central area of Vanuatu, we augmented the on-land network with two offshore sites using absolute pressure gauges. The sites - Wusi and Sabine Banks - are installed beneath altimetry satellite tracks, Wusi Bank on the over-riding plate and Sabine Bank on the subducting plate. The difference in the pressure records between the sites shows that Wusi Bank subsides by 11 +/- 3 mm/yr with respect to Sabine Bank. We combined the water depths derived from the pressure measurements with altimetry-derived sea-surface heights to tie these heights to a global reference frame: Wusi Bank subsides and Sabine Bank's vertical motion is near zero. Using a 2D elastic model and a finite-element code, we used the gradient of vertical deformation between the coast and the Wusi Bank site to discriminate between possible locked zone geometries. The best simple approximation is a 25° dipping, 30 km long fully locked zone, indicating that stress is currently accumulating west of Santo, Central Vanuatu. The movement of Wusi Bank is a key factor in constraining the dip and length of the locked zone, demonstrating the importance of offshore geodesy measurements.

Ballu, V.; Bouin, M.; Baillard, C.; Calmant, S.; Pelletier, B.; Crawford, W. C.; Kanas, T.; Garaebiti, E.

2012-12-01

234

The response of a flat plate boundary layer to an orthogonally arranged dielectric barrier discharge actuator  

NASA Astrophysics Data System (ADS)

The jetting characteristics of dielectric barrier discharge (DBD) actuators make these devices suitable for augmenting boundary layer flows. The associated change to the hydrodynamic stability of the fluid arising from the actuator provides a mechanism through which a DBD-based laminar flow control (LFC) system can be developed. Historically, DBD actuators with electrodes arranged parallel to each other have been used for LFC with mixed results. An alternative is to use an actuator with electrodes placed orthogonally to each other. Orthogonally arranged actuators exhibit different jetting characteristics to conventional ones, and as such understanding the effect that these actuators have on the mean velocity profile within a flat plate boundary layer is of significant interest to the development of DBD-based LFC technology. In this investigation, the velocity distribution within a flat plate boundary layer in a zero pressure gradient is measured in response to the operation of an orthogonally arranged actuator. The results suggest that significant thinning of the boundary layer can be realized with an orthogonally arranged actuator, over a short distance downstream of the device, and used in conjunction with a subtle suction effect, this thinning can be exacerbated. However, further downstream, rapid thickening of the layer, supported by a decrease in the shape factor of the flow suggests that the layer becomes unstable, in an accelerated fashion, to the presence of the actuator. Hence the stability of the layer is found to be significantly altered by the presence of the orthogonally arranged actuator, a requisite for a LFC system. However, since the actuator produces a destabilizing effect, the development of a successful LFC system based on orthogonal actuators will require further work.

Gibson, B. A.; Arjomandi, M.; Kelso, R. M.

2012-01-01

235

The memory of the accreting plate boundary and the continuity of fracture zones  

USGS Publications Warehouse

A detailed aeromagnetic anomaly map of the Mesozoic seafloor-spreading lineations southwest of Bermuda reveals the dominant magnetic grain of the oceanic crust and the character of the accreting boundary at the time of crustal formation. The magnetic anomaly pattern is that of a series of elongate lobes perpendicular to the fracture zone (flowline) trends. The linear sets of magnetic anomaly peaks and troughs have narrow regions of reduced amplitude anomalies associated with the fracture zones. During the period of Mesozoic geomagnetic polarity reversals (when 1200 km of central North Atlantic seafloor formed), the Atlantic accreting boundary consisted of stationary, elongate, spreading center cells that maintained their independence even though sometimes only minor spatial offsets existed between cells. Normal oceanic crustal structure was formed in the spreading center cells, but structural anomalies and discontinuities characteristic of fracture zones were formed at their boundaries, which parallel flowlines of Mesozoic relative plate motion in the central North Atlantic. We suggest that the memory for a stationary pattern of independent spreading center cells resides in the young brittle lithosphere at the accreting boundary where the lithosphere is weakest; here, each spreading center cell independently goes through its cylce of stress buildup, stress release, and crustal accretion, after which its memory is refreshed. The temporal offset between the peaks of the accretionary activity that takes place within each cell may provide the mechanism for maintaining the independence of adjacent spreading center cells through times when no spatial offset between the cells exists. ?? 1982.

Schouten, H.; Klitgord, K.D.

1982-01-01

236

Flowfield measurements in a separated and reattached flat plate turbulent boundary layer  

NASA Technical Reports Server (NTRS)

The separation and reattachment of a large-scale, two-dimensional turbulent boundary layer at low subsonic speed on a flat plate has been studied experimentally. The separation bubble was 55 cm long and had a maximum bubble thickness, measured to the height of the mean dividing streamline, of 17 cm, which was twice the thickness of the inlet boundary layer. A combination of laser velocimetry, hot-wire anemometry, pneumatic probing techniques, and flow visualization were used as diagnostics. Principal findings were that an outer inviscid rotational flow was defined which essentially convected over the blockage associated with the inner, viscously dominated bubble recirculation region. A strong backflow region in which the flow moved upstream 100 percent of the time was measured near the test surface over the central 35 percent of the bubble. A laminar backflow boundary layer having pseudo-turbulent characteristics including a log-linear velocity profile was generated under the highly turbulent backflow. Velocity profile shapes in the reversed flow region matched a previously developed universal backflow profile at the upstream edge of the separation region but not in the steady backflow region downstream. A smoke flow visualization movie and hot-film measurements revealed low frequency nonperiodic flapping at reattachment. However, forward flow fraction data at reattachment and mean velocity profiles in the redeveloping boundary layer downstream of reattachment correlated with backward-facing step data when the axial dimension was scaled by the distance from the maximum bubble thickness to reattachment.

Patrick, William P.

1987-01-01

237

Plate boundary forces at subduction zones and trench-arc compression  

NASA Astrophysics Data System (ADS)

Viscoelastic finite element modelling has been used to study the state of stress in the overriding and subducting plates meeting at a subduction zone. The subduction fault is included using the dual node technique. It is demonstrated that substantial horizontal deviatoric compressive stress occurs in the trench-arc region as a result of the downpull of the dense slab and the associated surface depression including the trench and other downflexing of the plates. This may be masked at the trench by bending stress. It is the lack of significant shearing stress along an unlocked subduction fault in the presence of this compressive stress that gives rise to the slab pull and trench suction plate boundary forces. Slab pull and trench suction were found to be of comparable magnitude within the range 1.0 to 4.0 × 10 12 N/m in models studied with vertical subduction, and there are indications that this may also apply when the slab dips at 45° as a result of viscous flow induced by rollback. When the slab dips beneath the arc-backarc region, it is shown that horizontal deviatoric compression can occur in this region contemporaneous with plate interior tension produced by trench suction. This suggests that backarc tension associated with Marianas type trench-arch systems may be related to the nearly vertical slab whereas backarc compression in the Chilean type may result from the low dip and small downpull of the slab. It is also shown that successive locking and unlocking of the subduction fault may give rise to large variations of stress in plate interiors.

Bott, M. H. P.; Waghorn, G. D.; Whittaker, A.

1989-12-01

238

Chemical and isotopic evidence of gas-influenced flow at a transform plate boundary: Monterey Bay, California  

USGS Publications Warehouse

Chemical and isotopic compositions of pore fluids document upward flow through communities of vesicomyid clams in Monterey Bay, California. Within the clam communities, the sulfate reduction zone is only 10 cm thick, and Ca and Mg concentrations decrease to values as low as 2.2 mM and 34.5 mM, respectively, at depths less than 30 cm below the sediment-water interface. Less than 5 m outside the communities, the base of the sulfate reduction zone is deeper than the greatest penetration of the cores (-30 cm), and Ca and Mg exhibit only minor changes from seawater values. The sediment exhibits no significant variation in grain size, mineralogy, organic carbon, nitrogen, or carbonate content throughout the region. The composition of pore fluid within clam communities results from upward flow of altered fluid rather than different diagenetic reactions within and outside the communities. Isotopically light dissolved inorganic carbon (DIC), with ??13C values ranging from -3.2 to -54.1???, could reflect carbon sources from either oxidized thermogenic methane and/or a mixture of oxidized microbial methane and solid organic carbon. The C1/(C2+C3) ratios (ranging from 34 to 1142) and the hydrogen and carbon isotopic compositions of methane (??D values of -109 to -156???; ??13C values of -30.6 to -86.6???) suggest that methane is primarily microbial but that a minor component could be thermally generated. Any thermogenic methane would have migrated from great depths, possibly >2 km. The presence of methane is likely to contribute to fluid flow by reducing the density of the fluids. Past fluid migration and venting are reflected by widespread carbonate mineralization at the sediment-water interface. This mineralization and the geographic distribution and proportions of microbial and thermogenic methane suggest that vent sites migrate when permeability is reduced during carbonate cementation. These results demonstrate that along with convergent and divergent plate boundaries, transform plate boundaries are characterized by fluid flow and that the flow may be widespread, occurring at sites away from fault zones.

Martin, J. B.; Orange, D. L.; Lorenson, T. D.; Kvenvolden, K. A.

1997-01-01

239

Seismicity and seismotectonics of the diffusive Iberian/African plate boundary: Horseshoe Abyssal Plain and Gorringe Bank  

NASA Astrophysics Data System (ADS)

In the area to the west of the Gibraltar Arc the plate boundary between Africa and Iberia is poorly defined. The deformation in the area is forced by the slow NW-SE convergence of 4 mm/yr between the oceanic domains of Iberia/Eurasia and Africa and is accommodated over a 200 km broad tectonically-active deformation zone. The region, however, is also characterized by large earthquakes and tsunamis, such as the 1969 Mw=7.9 Horseshoe Abyssal Plain earthquake and the November 1, 1755 Great Lisbon earthquake with an estimated magnitude of Mw~8.5. The exact location of the source of the 1755 Lisbon earthquake is still unknown. Recent work may suggest that the event occurred in the vicinity of the Horseshoe fault, an oblique thrust fault. However, estimates of tsunami arrival times suggested a source near the Gorringe Bank, a ~180 km-long and ~70 km-wide ridge that has a relieve of ~5000 m. Deep Sea Drilling (DSDP) and rock samples indicated that the bank is mainly composed of serpentinized peridotites with gabbroic intrusions, perhaps being created by overthrusting of the Horseshoe Abyssal Plain onto the Tagus Abyssal Plain in NW direction. Further, the Horseshoe Abyssal Plain is marked by the presence of compressive structures with a roughly NE-SW orientation and E-W trending, segmented, crustal-scale, strike slip faults that extend from the Gorringe Bank to the Gibraltar Arc in the eastern Gulf of Cadiz, which were called "South West Iberian Margin" or SWIM faults. The fault system may mark a developing Eurasia-Africa plate boundary. Two local seismic networks were operated in the area. First, a network of 14 ocean-bottom seismometers (OBS) was operated between April and October 2012 in the vicinity of the Horseshoe fault between 10°W to 11°W, and 35°50'N to 36°10'N. From October 2013 to March 2014 a second network of 15 OBS monitored seismicity at the Gorringe Bank. Both networks benefitted from seismic stations operated in Portugal. The first network provided in the order of 100 locale earthquakes occurring with the network. Most earthquakes in the Horseshoe occurred at a depth of 40-60 km, either in oceanic or unroofed continental mantle. The large source depth of events observed in the Horseshoe Abyssal Plain supports the idea that large catastrophic earthquakes, like the Great Lisbon earthquake of 1755, may indeed occur in the area.

Grevemeyer, Ingo; Lange, Dietrich; Matias, Luis

2014-05-01

240

Reconstruction convergence and speed enhancement in electrical impedance tomography for domains with known internal boundaries.  

PubMed

An improved approach for electrical impedance tomography (EIT) image reconstruction, based on modifying the forward and inverse solutions, is proposed. In this approach, the EIT forward problem is solved via the finite element method (FEM) using two types of elements. The inverse problem is solved by the modified Newton-Raphson method, whereas the condition number of the Hessian matrix is being monitored. At the early stage of the reconstruction, first-order elements are used, and if the condition number exceeds the allowable limit, the algorithm restarts. Otherwise, if the reconstruction error becomes lower than a predefined threshold, second-order elements are employed in the forward solution in order to preserve the precision of the final results. The latter stage converges in very few iterations. Since the solution speed with the first-order FEM is considerably higher than the second-order FEM, the reconstruction speed improves considerably by this approach, whereas the accuracy of the results is guaranteed by the well-conditioned Hessian matrix. Numerical simulations and experiments are followed by comparisons with other reconstruction methods which demonstrate the reliability and high solution speed of this approach. According to the results, the convergence of the proposed method is significantly improved, and its speed is 2-200 times higher than the previously developed methods with the same level of precision. PMID:20938064

Rezajoo, Saeed; Hossein-Zadeh, Gholam-Ali

2010-11-01

241

What on Earth is Plate Tectonics?  

NSDL National Science Digital Library

This web site was put together by the U.S.G.S. (United States Geological Survey) and the N.P.S. (National Park Service) and provides an overview of plate tectonics. It begins by explaining about the Earth's core, mantle, and crust. It then discusses the crustal plates and the types of plate boundaries (convergent, divergent and transform). The lesson ends with paleogeographic reconstructions of plate distributions from the past 650 million years.

242

Divergent plate boundaries and crustal spreading on Venus: Evidence from Aphrodite Terra  

NASA Technical Reports Server (NTRS)

The modes of lithospheric heat transfer and the tectonic styles may differ between Earth and Venus, depending on how the high surface temperature (700 K = 430 C), dense and opaque atmosphere (approx. 10 MPa = 100 bars), lack of water oceans, and the other known ways in which Venus differs from Earth, influence basic lithospheric processes, thermal gradient, upper mantle temperature, thermal and chemical evolution, and convection. A fundamental question is whether the lithosphere of Venus is horizontally stable, like the other terrestrial planets, or is mobile like that on Earth. The variety of characteristics, their integrated relationships, and their predictable behavior throughout Western Aphrodite Terra are similar to those features known to occur in association with the terrestrial seafloor at spreading centers and divergent plate boundaries. It is concluded that Western Aphrodite Terra represents the site of crustal spreading centers and divergent plate boundaries. The extent of similar characteristics and processes elsewhere on Venus outside of the 13,000 km long Western and Eastern Aphrodite Terra rise is unknown at the present, but their presence in other areas of the equatorial highlands, suggested from recent analysis, may be tested with forthcoming Magellan data.

Crumpler, L. S.; Head, James W.

1989-01-01

243

Tectonic evolution of the Pacific margin of Antarctica 2. Structure of Late Cretaceous-early Tertiary plate boundaries in the Bellingshausen Sea from seismic reflection and gravity data  

NASA Astrophysics Data System (ADS)

Interpretations of multichannel seismic (MCS) reflection and potential field data suggest that some prominent gravity anomalies in the Bellingshausen Sea are associated with plate boundaries that were active during the Late Cretaceous and early Tertiary. Between 83° and 93°W, a belt of negative anomalies extends along the West Antarctic continental slope, which we term the continental slope gravity anomaly (CSGA). MCS profiles show that the CSGA coincides with an acoustically opaque structural high imaged beneath the lower slope. We interpret this structure as the upper part of an accretionary prism which formed during southward subduction of the Phoenix and Charcot plates, before Chatham Rise separated from West Antarctica. MCS profiles crossing the same margin to the northeast show no evidence of an extensive buried accretionary prism, but instead reveal an abrupt northeastward steepening of the continental slope near 78°W. We attribute this change in tectonic style, at least in part, to subduction erosion resulting from subduction of rough oceanic basement which formed at the Antarctic-Phoenix ridge after an abrupt decrease in spreading rate at chron 23r (52 Ma). Near 95°W, the Bellingshausen gravity anomaly (BGA) consists of a prominent low-high gravity couple which crosses the West Antarctic continental shelf, slope, and rise. The BGA corresponds to a buried asymmetric basement trough, where Cretaceous oceanic basement dips beneath more elevated basement to the east. The trough probably formed after subduction of Charcot plate ocean floor stalled at the nearby Antarctic Peninsula margin, near the end of the Cretaceous Normal Superchron. Ocean floor to the east of the BGA became attached to the Antarctic Peninsula, and the BGA trough subsequently accommodated a small amount of convergent motion between the Antarctic Peninsula and the ocean floor to the west (initially part of the Marie Byrd Land plate and later part of the Bellingshausen plate). Tectonism probably ceased at the BGA at chron 27 (61 Ma), as a result of a general plate reorganization in the South Pacific.

Cunningham, Alex P.; Larter, Robert D.; Barker, Peter F.; Gohl, Karsten; Nitsche, Frank O.

2002-12-01

244

Rayleigh wave tomography of the Pacific-North American plate boundary in Southern California  

NASA Astrophysics Data System (ADS)

Southern California is the location of a unique transform plate boundary on land that divides the North American and the Pacific plate. This tectonic system was formed during the Miocene period with the subduction of the Farallon plate and the East Pacific Rise beneath California roughly 30 Ma years ago. However, the stresses surrounding this tectonic system are only partially understood due to lack of data availability offshore which makes up half of this plate boundary. Here we employ seismic tomography methods using land and offshore data to consider tectonic stresses, mantle flow dynamics, and earthquake hazard analysis in and surrounding southern California. We use Rayleigh waves recorded by an array of 34 ocean bottom seismometers (OBS) deployed as part of the ALBACORE project offshore southern California on 18-32 Ma seafloor. The OBS's recorded for a 12 month duration from August 2010 to 2011 and are combined with 82 land stations which recorded data simultaneously from the southern California Integrated Seismic Network. We analyze ~100 teleseismic events at distances ranging from 30° to 120° with good signal-to-noise ratios for magnitudes of Mw ? 5.9. The events exhibit good azimuthal distribution and enable us to solve simultaneously for Rayleigh wave phase velocities and azimuthal anisotropy. Fewer events occur at NE back-azimuths due to the lack of seismicity in central North America. We consider seismic periods between 16 - 80 seconds. The inversion technique considers non-great circle path propagation by representing the arriving wave field as two interfering plane waves. Preliminary results indicate that phase velocities for periods above 20s are approximately 0.8 % lower than previous studies for the seafloor age bin 20-52 Ma that used oceanic raypaths recorded by land stations. The strength of anisotropy is consistent at 2.5 % for nearly all periods within error. The dominant direction of azimuthal anisotropy is not consistent with Pacific plate motion direction. The fast direction for periods below 33 s displays an E-W azimuth that agrees with shear wave splitting results previously reported from island stations. At longer periods, anisotropy indicates a counter clockwise rotation in fast direction with increasing depth and period. This rotation is consistent with a model where rotation is maximum at the surface where the E-W trending Transverse Ranges show 90° to 110° rotation and is minimum for mantle depths at 100-150 km, suggesting that the mantle is being rotated by drag from the surface.

Rathnayaka, S.; Escobar, L.; Weeraratne, D. S.; Kohler, M. D.

2013-12-01

245

Experimental study of boundary layer transition with elevated freestream turbulence on a heated flat plate  

NASA Technical Reports Server (NTRS)

A detailed investigation to document momentum and thermal development of boundary layers undergoing natural transition on a heated flat plate was performed. Experimental results of both overall and conditionally sampled characteristics of laminar, transitional, and low Reynolds number turbulent boundary layers are presented. Measurements were acquired in a low-speed, closed-loop wind tunnel with a freestream velocity of 100 ft/s and zero pressure gradient over a range of freestream turbulence intensities (TI) from 0.4 to 6 percent. The distributions of skin friction, heat transfer rate and Reynolds shear stress were all consistent with previously published data. Reynolds analogy factors for R(sub theta) is less than 2300 were found to be well predicted by laminar and turbulent correlations which accounted for an unheated starting length. The measured laminar value of Reynolds analogy factor was as much as 53 percent higher than the Pr(sup -2/3). A small dependence of turbulent results on TI was observed. Conditional sampling performed in the transitional boundary layer indicated the existence of a near-wall drop in intermittency, pronounced at certain low intermittencies, which is consistent with the cross-sectional shape of turbulent spots observed by others. Non-turbulent intervals were observed to possess large magnitudes of near-wall unsteadiness and turbulent intervals had peak values as much as 50 percent higher than were measured at fully turbulent stations. Non-turbulent and turbulent profiles in transitional boundary layers cannot be simply treated as Blasius and fully turbulent profiles, respectively. The boundary layer spectra indicate predicted selective amplification of T-S waves for TI is approximately 0.4 percent. However, for TI is approximately 0.8 and 1.1 percent, T-S waves are localized very near the wall and do not play a dominant role in transition process.

Sohn, Ki-Hyeon; Reshotko, Eli

1991-01-01

246

Development of an Auto-Convergent Free-Boundary Axisymmetric Equilibrium Solver  

SciTech Connect

The calculation of the magnetic flux given an assumed value for the current profile in axisymmetric toroidal plasmas is essential in studying the effects of various magnetohydrodynamic (MHD) instabilities upon controlled fusion. To this end, an iterative, modular algorithm coupled with a fast, direct elliptic solver for the Grad-Shafranov equation has been used to reconstruct the desired free-boundary equilibrium solution. This free-boundary Grad-Shafranov (FBGS) equilibrium algorithm is modified with the application of the von Hagenow method for determining the flux on the computational boundary, greatly reducing the time cost from O(N3) to O(N2 ln N) machine operations as compared to current Green’s function methods. The inherent variance in implementing the von Hagenow method gives a mean error bound of 0.1 percent with respect to the normal Green’s method. The improvements will allow the grid resolution to be increased efficiently and automatically to reduce the maximum Grad-Shafranov error to values needed for accurate stability calculations on a more effective time scale.

Huang, J.; Menard, J.

2006-01-01

247

What happens to the Juan de Fuca plate boundary beneath northern Cascadia? Insight into the methamorphism of the oceanic crust  

NASA Astrophysics Data System (ADS)

In subduction zones, the plate boundary is the locus where the largest earthquakes occur worldwide. The exact knowledge of the geometry of the plate boundary and the physical properties of the materials brought together in contact are fundamental to understand the earthquake nucleation process and to better asses the seismic hazard in densely populated areas. Due to the metamorphism of the subducted materials and the release of fluids from the subducted plate (e.g. breakout of the serpentinized oceanic upper mantle), the seismic properties of the materials distributed along the plate boundary change with depth (i.e. at different age of subduction). Thus, the clear recognition of the plate boundary at depth using indirect method (e.g. seismic tomography) might be a very complex task. In Northern Cascadia, the position of the plate boundary between the North America (NAM) plate and the Juan de Fuca (JdF) plate is still debated. While along the coast, plate boundary models almost agree, differences in the estimated depth of such interface arise in-land between different models, exactly where large earthquakes enucleate. In this study, we investigate the seismic properties of the subducted JdF crust as it plunges in the upper mantle beneath Northern Cascadia. Harmonic decomposition of a huge Receiver function data-set is used to image both isotropic and anisotropic structures along a trench-normal profile, to better constrain the metamorphism of the crustal materials during the subduction process. The analysis of the seismic anisotropy of the materials is fundamental to better recognize the different components of the subducted plate, where large changes in the seismic velocity of the materials are expected. Our results confirm the 2-layer structure of the JdF crust: basalts over gabbros, and allow us to depict their metamorphism as they plunge into the upper mantle. In the western part of out profile an East-dipping low S-velocity layer is interpreted as fluid-filled basalts, in a region where the uppermost interface of the JdF is sealed. In such region, the JdF upper mantle is strongly anisotropic and the occurrence of intermediate-depth events suggests its progressive de-serpentinization. Further East, fluids coming from the JdF upper mantle trigger the metamorphism of the JdF crust. In the same region, the sealed boundary is finally cracked and fluids hydrate the lower-crust of the NAM plate. Finally, in the eastern portion of our profile, our results clearly depict the final eclogization of the JdF crust and the fluid migration in the NAM upper mantle.

Piana Agostinetti, N.; Miller, M. S.

2012-12-01

248

Optimizing the electrode size of circular bimorph plates with different boundary conditions for maximum deflection of piezoelectric micromachined ultrasonic transducers.  

PubMed

The effect of plate electrode area on the deflection of a symmetric circular bimorph piezoelectric micromachined ultrasonic transducer (pMUT) with clamped and simply supported boundary conditions was studied for the first time. Distinct plate displacement shape functions were defined for the regions underneath and outside the active electrodes. The plate shape functions were solved analytically using classic plate theory in conjunction with the external boundary conditions and the internal ones between the two regions in order to calculate the exact plate displacement under both external voltage stimulus and acoustic pressure. The model was used to study the effect of the electrode area on the overall plate deflection per unit input voltage such that the electromechanical coupling is optimized. While the center plate deflection increased monotonically with the electrode area for a simply supported plate, it followed a parabolic shape for a clamped one with a maximum deflection when the electrode radius covered 60% of the total plate radius. The simply supported plate exhibited four times the plate deflection capability of its clamped counterpart, when both are operating at their optimal electrode size. Both an experimental clamped bimorph aluminum nitride (AlN) pMUT, recently reported in the literature, and Finite Element Modeling (FEM) were used to verify the developed model. The theoretical model predicted a static displacement per unit voltage of 10.9nm/V and a resonant frequency of 196.5kHz, which were in excellent agreement with the FEM results of 10.32nm/V and 198.5kHz, respectively. The modeling data matched well with the experimental measurements and the error ranged from 2.7-22% due to process variations across the wafer. As such, the developed model can be used to design more sensitive pMUTs or extract the flexural piezoelectric coefficient using piezoelectrically actuated circular plates. PMID:22959848

Sammoura, Firas; Smyth, Katherine; Kim, Sang-Gook

2013-02-01

249

Tour of Park Geology: Plate Tectonics  

NSDL National Science Digital Library

This National Park Service (NPS) site provides links to geology field notes providing information about National Parks, National Monuments, and National Recreation Areas that have to do with plate tectonics. The site also has illustrations and descriptions of different plate boundaries. The parks are divided into categories depending on which type of plate boundary they are located on. This includes divergent boundaries(active and ancient), convergent boundaries (ocean-ocean, continent-continent, continent-ocean), transform faults, hot spots, and accreted terrains. Parks referenced include Virgin Islands National Park, Florissant Fossil Beds National Monument, Hawaii Volcanoes National Park, and many more.

250

Summary of the stratigraphy and structural elements related to plate convergence of the Quetta-Muslim Bagh-Sibi region, Balochistan, west-central Pakistan  

USGS Publications Warehouse

The four major faults that bound the structural terrane are the Frontal (F), Ghazaband-Zhob (GZ), Gwal-Bagh (GB), and Chaman (C) faults. Four major periods of deformation are recognized: (1) emplacement of ophiolitic rocks onto the continental margin of the India plate; (2) convergence of the India-Eurasia plates; (3) deposition of Tertiary-Quaternary molasse units followed by major folding and thrusting, and formation of strike-slip faults; and (4) deposition of Pleistocene molasse units with subsequent folding, thrusting, and strike-slip motion that continues to the present.

Maldonado, Florian; Mengal, Jan M.; Khan, Shahid H.; Warwick, Peter D.

2011-01-01

251

Thermal State of the Seismogenic Plate Boundary in Southern Chile, 36 -- 46 °S  

NASA Astrophysics Data System (ADS)

According to current models of great subduction earthquakes, the area of the ruptured zone, and therefore the magnitude of the event, is controlled by the thermal structure of the plate boundary; updip and downdip limits of the seismogenic zone coincide with temperatures of 100 - 150 °C and 350 - 450°C, respectively. From this point of view, the 1960 Chile earthquake (M_W=9.5), which is the largest earthquake ever been recorded, was not only an outstanding event in respect to its magnitude. Also, the thermal structure of the young oceanic crust subducted along the ~1000 km long rupture area north of the Chile Triple Junction is remarkable, since considerable variability is caused by ocean floor ages ranging from ~0 - 30 Ma. Being part of the multi-disciplinary and multi-institutional project TIPTEQ (from The Incoming Plate to mega- Thrust EarthQuake processes), we present the correlation of lateral variations in the thermal structure of the 1960 Chile earthquake rupture area with seismic activity. Finite element method (FEM) models based on the Comsol Multiphysics code are used to estimate the thermal state of the plate boundary. To constrain the FEM models, scarce existing heat flux data were supplemented by 63 successful deployments of violin bow type heat flux probes during RV Sonne cruise 181-1b from December 2004 through January 2005. On the continental slope, additional constrains on the heat flux were derived from abundant bottom simulating reflectors (BSRs) found in seismic reflection data. Geometry information and seismic activity were obtained from TIPTEQ and Subduction Processes Off-shore Chile (SPOC) local seismological networks along the rupture area. From heat flux measurements on the incoming plate, which are generally lower than expected from conductive cooling models, we inferred advective cooling by circulating fluids in the upper oceanic crust and effects of rapid sedimentation close to the trench. These processes had to be taken into account by the numerical models to estimate the updip limit of the seismogenic zone.

Heesemann, M.; Grevemeyer, I.; Villinger, H. W.; Contreras-Reyes, E.; Scherwath, M.; Völker, D.

2006-12-01

252

The giant coastal landslides of Northern Chile: Tectonic and climate interactions on a classic convergent plate margin  

NASA Astrophysics Data System (ADS)

Documented for the first time are an extensive suite of late Neogene giant terrestrial coastal landslides along the classic convergent margin of western South America (18° to 24° south). These are remarkable in terms of their unusual abundance and atypical setting, such failures previously being linked with oceanic volcanic edifices or over-steepened glaciated coastlines. Located within the hyper-arid Coastal Cordillera of the Atacama Desert of Northern Chile we report the presence of more than 60 individual large-scale landslides with individual volumes up to 9 km3 developed over a horizontal coastline distance of some 650 km. These landslides were emplaced as a combination of rock avalanches and multiple rotational failures. The majority terminated directly into the Pacific - likely generating significant tsunami hazard to the Chilean and south Peruvian coastline in a region which is today considered to be part of a notorious seismic gap. The proliferation and scale of these Late Neogene giant landslides in this actively uplifting, hyperarid terrain suggests they are the main geomorphic agent for relief reduction, probably triggered by megathrust earthquakes and potentially providing a unique palaeoseismic archive. The temporal and spatial distribution of these giant landslides corresponds with a period of surface steepening of the forearc wedge in the Central Andes and south to north differential uplift associated with factors such as aseismic ridge subduction. The resulting surface gradient increases, combined with the persistent climatic aridity of the region, have served to limit effective relief-reducing geomorphic processes in this oversteepened terrain to large-scale landsliding. The phenomena documented here geospatially link previously recognised large-scale slope failures from the off-shore environment and higher altitude areas of the Andean forearc, suggesting that large-scale landsliding is capable of transferring sediment on a regional scale to the off-shore Peru-Chile trench. This has implications for the friction of the subducting Nazca plate and associated seismicity and uplift.

Mather, Anne E.; Hartley, Adrian J.; Griffiths, James S.

2014-02-01

253

Kinematics of the northern Walker Lane: An incipient transform fault along the Pacific–North American plate boundary  

Microsoft Academic Search

In the western Great Basin of North America, a system of dextral faults accommodates 15%-25% of the Pacific-North American plate motion. The northern Walker Lane in northwest Nevada and northeast California occupies the northern terminus of this system. This young evolving part of the plate boundary offers insight into how strike-slip fault systems develop and may reflect the birth of

James E. Faulds; Christopher D. Henry; Nicholas H. Hinz

2005-01-01

254

Logistical Support for the Installation of the Plate Boundary Observatory GPS and Borehole Strainmeter Networks  

NASA Astrophysics Data System (ADS)

The Plate Boundary Observatory (PBO), part of the NSF-funded EarthScope project, is designed to study the three- dimensional strain field resulting from deformation across the active boundary zone between the Pacific and North American plates in the western United States. To meet these goals, UNAVCO will install 880 continuous GPS stations, 103 borehole strainmeter stations, 28 tiltmeters, and five laser strainmeters by October 2008. Such a broad network presents significant logisitical challenges, including moving supplies, equipment, and personnel around 6 million square kilometers, and this requires accurate tracking and careful planning. The PBO logistics chain includes the PBO headquarters at UNAVCO in Boulder, Colorado and five regional offices in the continental United States and Alaska, served by dozens of suppliers spread across the globe. These offices are responsible for building and maintaining sites in their region. Most equipment and supplies first arrive in Boulder, where they are tagged and entered into a UNAVCO-wide equipment database, assembled and quality checked as necessary, and sent on to the appropriate regional office. Larger items which are costly to store and ship from Boulder, such as batteries or long sections of stainless steel pipe and bar required for monuments, are shipped directly from the supplier to each region as needed. These supplies and equipment are also tracked through the ordering, delivery, installation, and maintenance cycle via Earned Value Management techniques which allow us to meet NSF and other Federal procurement rules. Early prototypes and assembly configurations aid the development of material and supply budgets. A thorough understanding of Federal procurement rules at project start up is critical as the project moves forward.

Kurnik, C.; Austin, K.; Coyle, B.; Dittmann, T.; Feaux, K.; Friesen, B.; Johnson, W.; Mencin, D.; Pauk, B.; Walls, C.

2007-12-01

255

The Formation of the Betic-Alboran System in the Iberia-Africa Plate Boundary: a New Kinematic Evolution Model  

NASA Astrophysics Data System (ADS)

Several geodynamic models have been proposed so far to explain the origin and evolution of the Betic-Rif arcuate orogeny and the inner Alboran back-arc basin. Many of these models propose that the Alboran domain underwent a large westward drifting (> 600 km) driven by a subduction rollback, eventually resulting in a symmetric configuration in both the S-Iberia and N-African margins. Alternative models with a more autochthonous component assume that the Oligocene subduction trench extended continuously along the whole Iberian Mediterranean margin from the present Gibraltar arc to the Alps. Common assumptions to all these models are: i) the initial time is about 35 Ma (Eocene-Oligocene), ii) the plate boundary is continuous and non-segmented, iii) the initial subduction polarity is NW-dipping, and iv) the slab must underwent a twisted roll-back to explain the present position of the HP-LT metamorphic rocks involving slab rupture, detachment and tearing. Recent geophysical models based on seismic data, tomography and potential fields draw an arcuate mantle slab restricted below the Betic-Rif orogen, dipping towards the E below the Gibraltar Strait and turning to the SE and S beneath the Betics. In addition, the crust beneath the northern Moroccan margin shows a smooth thinning toward the Alboran basin whereas the southern Iberian margin presents a much sharper thinning. These findings put severe limitations to some of the proposed models and open room for new kinematic proposals. One of the most recent models is based on the following considerations: i) the reconstruction starts in Late Cretaceous times at the onset of northern Africa convergence, ii) displacements and initial configuration are based on plate reconstructions of the Atlantic-Ligurian-Tethys region, and iii) the model assumes that subduction polarity changes laterally from NW-dipping in the Algerian segment to SE-dipping in the Betic-Rif segment. Apart from its simplicity, this model requires a moderate NW to W drifting of the HP-LT metamorphic complexes formed by limited subduction and exhumation, fulfills the imaged crustal and mantle asymmetries, and is compatible with the main geological structures in the region. Cartoon showing the evolution of the Betic-Alboran-Rif system at 9 Ma.

Fernandez, M.; Verges, J.

2013-12-01

256

An analytical solution for a multilayered magneto-electro-elastic circular plate under simply supported lateral boundary conditions  

NASA Astrophysics Data System (ADS)

We derive, in this paper, the analytical solution for a three-dimensional transversely isotropic axisymmetric multilayered magneto-electro-elastic (MEE) circular plate under simply supported boundary conditions. The state space vector, the finite Hankel transform and propagating matrix methods are utilized together to obtain the full-field solutions for the MEE plate made of piezoelectric (PE) and piezomagnetic (PM) layers. Numerical examples for three-layered and five-layered PE/PM composites with different stacking sequences and under different loading conditions are presented and discussed. These results can serve as benchmark solutions for future numerical analyses of layered MEE plates.

Wang, R.; Han, Q.; Pan, E.

2010-06-01

257

Direct numerical simulation for a time-developing natural-convection boundary layer along a vertical flat plate  

Microsoft Academic Search

Direct numerical simulations were performed for the transitional and turbulent natural-convection boundary layer for air and water along a hot vertical flat plate. The numerical results for water well reproduce the vortex-like structures as observed experimentally in the thermal field for a high Prandtl-number fluid. When the calculated values are evaluated with the integral thickness of the velocity boundary layer

Mohammad Zoynal Abedin; Toshihiro Tsuji; Yasuo Hattori

2009-01-01

258

Experimental Studies on Wake-Induced Bypass Transition of Flat-Plate Boundary Layers under Favorable and Adverse Pressure Gradients  

Microsoft Academic Search

This study investigates wake-induced bypass transition of boundary layers on a flat plate which is subjected to favorable and adverse pressure gradients. Inlet free-stream turbulence level is controlled with a turbulence grid. Detailed boundary layer measurements are executed by use of a single hot-wire probe. The main focus of this paper is on how and to what extent the wake-induced

Eitaro Koyabu; Ken-Ichi Funazaki; Manabu Kimura

2005-01-01

259

Active faulting in northern Chile: ramp stacking and lateral decoupling along a subduction plate boundary?  

NASA Astrophysics Data System (ADS)

Two large features parallel to the coastline of northern Chile have long been suspected to be the sites of young or active deformation: (1) The 700-km long Coastal Scarp, with average height (above sea level) of about 1000 m; (2) The Atacama Fault zone, that stretches linearly for about 1100 km at an average distance of 30-50 km from the coastline. New field observations combined with extensive analysis of aerial photographs demonstrate that both the Coastal Scarp and the Atacama Fault are zones of Quaternary and current fault activity. Little-degraded surface breaks observed in the field indicate that these fault zones have recently generated large earthquakes ( M = 7-8). Normal fault offsets observed in marine terraces in the Coastal Scarp (at Mejillones Peninsula) require tectonic extension roughly orthogonal to the compressional plate boundary. Strike-slip offsets of drainage observed along the Salar del Carmen and Cerro Moreno faults (Atacama Fault system) imply left-lateral displacements nearly parallel to the plate boundary. The left-lateral movement observed along the Atacama Fault zone may be a local consequence of E-W extension along the Coastal Scarp. But if also found everywhere along strike, left-lateral decoupling along the Atacama Fault zone would be in contradiction with the right lateral component of Nazca-South America motion predicted by models of present plate kinematics. Clockwise rotation with left-lateral slicing of the Andean orogen south of the Arica bend is one way to resolve this contradiction. The Coastal Scarp and the Atacama Fault zone are the most prominent features with clear traces of activity within the leading edge of continental South America. The great length and parallelism of these features with the subduction zone suggest that they may interact with the subduction interface at depth. We interpret the Coastal Scarp to be a west-dipping normal fault or flexure and propose that it is located over an east-dipping ramp stack at the subduction interface. The similar flexure at the western edge of the Altiplano may have the same origin. Ramp stacking along the subduction zone, a mechanism disregarded so far, may be an important thickening process in the Andes and perhaps the basic cause of the uplift of the Altiplano.

Armijo, Rolando; Thiele, Ricardo

1990-04-01

260

Natural Convective Boundary Layer Flow Over a Nonisothermal Vertical Plate Embedded in a Porous Medium Saturated With a Nanofluid  

Microsoft Academic Search

Nanofluid refers to a liquid containing a dispersion of submicronic solid particles or nanoparticles. Nanofluids display a thermal conductivity enhancement. This phenomenon suggests the possibility of using nanofluids in electronic cooling and advanced nuclear systems. In this article, a boundary layer analysis is presented for the natural convection past a nonisothermal vertical plate in a porous medium saturated with a

Rama Subba Reddy Gorla; Ali Chamkha

2011-01-01

261

Group method analysis of unsteady free-convective laminar boundary-layer flow on a nonisothermal vertical flat plate  

Microsoft Academic Search

The transformation group theoretic approach is applied to present an analysis of the problem of unsteady laminar free convection from a non-isothermal vertical flat plate. The application of two-parameter groups reduces the number of independent variables by two, and consequently the system of governing partial differential equations with boundary conditions reduces to a system of ordinary differential equations with appropriate

M. B. Abd-El-Malek; Y. Z. Boutros; N. A. Badran

1990-01-01

262

Numerical Simulation of the Control of Wave Packet Disturbances in the Boundary Layer on a Flat Plate  

Microsoft Academic Search

The control of the transition from laminar to turbulent flow in a boundary layer of a flat plate is investigated using numerical simulations. The numerical model is based on the incompressible Navier-Stokes equations, which is coupled with the energy equation through the temperature dependent viscosity. A fully implicit finite difference spectral method was used to solve the governing equations. The

Peter Aloisius Dittrich

1991-01-01

263

Earthquake Locations and Style of Faulting in an Active Arc-Continent Plate Boundary: the Chihshang Fault of Eastern Taiwan  

Microsoft Academic Search

The Chihshang fault with a surface slip velocity of 2.2 centimeters per year is the most active segment of the collision boundary between Eurasia and the Luzon arc of the Philippine Sea plate in eastern Taiwan. Albeit its high slip rate, there has not been any significant earthquake occurred along the Chihshang fault since 1951, and the fault now appears

H. Chen; R. Rau

2002-01-01

264

Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions  

Microsoft Academic Search

We use Global Positioning System (GPS) velocities and stress orientations inferred from seismicity to invert for the distribution of slip on faults in the southern California plate-boundary region. Of particular interest is how long-term slip rates are partitioned between the Indio segment of the San Andreas fault (SAF), the San Jacinto fault (SJF) and the San Bernardino segment of the

Thorsten W. Becker; Jeanne L. Hardebeck; Greg Anderson

2005-01-01

265

Constraints on fault slip rates of the southern California plate boundary from GPS velocity and stress inversions  

Microsoft Academic Search

SUMMARY We use Global Positioning System (GPS) velocities and stress orientations inferred from seis- micity to invert for the distribution of slip on faults in the southern California plate-boundary region. Of particular interest is how long-term slip rates are partitioned between the Indio segment of the San Andreas fault (SAF), the San Jacinto fault (SJF) and the San Bernardino segment

Thorsten W. Becker; Jeanne L. Hardebeck; Greg Anderson

2005-01-01

266

Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacic: computer-based reconstructions, model and animations  

E-print Network

Cenozoic geological and plate tectonic evolution of SE Asia and the SW Paci®c: computer A plate tectonic model for the Cenozoic development of the region of SE Asia and the SW Paci reconstruction. Plate boundaries shifted rapidly in the Cenozoic. During convergence of the major plates

Royal Holloway, University of London

267

The Plate Boundary Observatory Borehole Network: Geologic Resources from Drilling and Logging  

NASA Astrophysics Data System (ADS)

The Plate Boundary Observatory Strainmeter Borehole Network has a total of 79 operational boreholes, with depths drilled from 420 to 800 feet. All drill cuttings, core samples and logs are stored and catalogued. The cuttings for each successful borehole were recently photo documented and will be placed on the UNAVCO website to be readily available to the public, as well as to request samples. The drill cuttings were collected in 10 foot intervals, and in Yellowstone they were collected in five foot intervals. The extent of the borehole network includes sites near the San Jacinto fault, San Andreas Fault, throughout the Cascadia region, Mt St Helens and Yellowstone. These locations provide a wide array of tectonic and volcanic environments. In the case of Yellowstone, the park has not been drilled in for four decades. Due to the circulation of hot fluids, holes are at a shallower depth ( > 420 feet). These cuttings provide a resource of understanding the history and dynamics of fluid interaction in Yellowstone. Along the San Jacinto fault and San Andreas fault, these cuttings can help to build better models of the fault dynamics through evaluating the stratigraphy, fractures, rock strength, structural geology and fluid interaction near and along the fault zones. The stranmeter sites in the Pacific NW were chosen for the subduction zone, and are therefore not near a major plate boundary. They could instead be used to understand local regional fault dynamics, stratigraphy, structural geology and volcanic history of the NW. Presented will be examples of interest from each region, from cuttings, core, logs, to correlated network observations. For example, a site on the San Jacinto fault, near Anza has recorded creep events. This site is the closest to the fault and during drilling fault gouge was observed. While in Parkfield, cuttings and core reveal different fault blocks for sites that are 1000 feet apart in distance. As UNAVCO cannot provide any analysis on these samples, the documentation and variability of these resources will be presented. The availability of these resources and an interest of understanding the hydrology and structural geology could provide new incite for understanding strike slip faulting as well as additional resources for understanding volcanic history.

Johnson, W.; Van Boskirk, E.; Mencin, D.; Gottlieb, M. H.; Pyatt, C.; Hodgkinson, K. M.; Fox, O.; Gallaher, W. W.; Borsa, A. A.

2011-12-01

268

Analysis of and results from the GPS component of the Plate Boundary Observatory  

NASA Astrophysics Data System (ADS)

The first GPS station installed by the Plate Boundary Observatory (PBO) component of the National Science Foundation (NSF) Earthscope program was installed and started operation in January 2004. Since then over 1100 new GPS stations have been installed and combined with over 300 pre-existing GPS stations to form PBO. Analysis of the data from this network is performed daily, with one-day latency, using rapid orbit products from the International GNSS Service (IGS) and weekly, with ~2 week latency, using the final IGS product. A supplemental analysis is also preformed with 12-week latency to add to the final solution data from sites that were not available when the first finals were run. The median weighted root-mean-square (WRMS) scatters of the position results from the combined analyses of these data performed by two different GPS analysis programs, GAMIT at New Mexico Tech and GIPSY at Central Washington University and combined with GLOBK at MIT, are less than 1 mm in North and East (NE) and 3 mm for vertical (U) over monthly durations. The WRMS scatters of the position residuals about linear trends, with offsets for earthquakes and antenna changes removed, from all results processed thus far, ~8 years of data for longest running sites, are ~1.5 mm NE and 4.5 mm U. The top 10% of sites have short period scatters (month duration) of 0.5 mm NE and 1.9 mm U, while the long-term scatters increase to 0.8 mm in NE and 3.3 mm U. The largest RMS sites are generally in volcanic areas and/or affected by snow and ice on the antennas. All of the data from PBO and from an additional 600 GPS sites are being re-processed with data back to 1996 being included in the reprocessing. In this paper, we will present results from this re-processing in terms of secular rates across the Pacific/North America plate boundary and non-secular signals arising from earthquakes (co- and post-seismic deformation) and other natural and human-induced processes.

Herring, T.; King, R. W.; Floyd, M. A.; Murray, M. H.; Melbourne, T. I.; Santillan, V. M.; Mattioli, G. S.; Phillips, D. A.; Puskas, C. M.

2012-12-01

269

Plate tectonics and offshore boundary delimitation: Tunisia-Libya case at the International Court of Justice  

SciTech Connect

Advances in the technology for exploiting resources of the oceans, particularly recovery of hydrocarbons and minerals in deep water, is benefiting a growing number of nations. At the same time, however, economic and political pressures have induced concern and there is now a much increased emphasis on jurisdiction to divide the offshore areas between the 132 coastal nations. Negotiations affect research operations at sea and, in consequence, marine scientists have been made aware of offshore problems as highlighted by the Law of the Sea Treaty (UNCLOS III) and complications arising from the legal versus scientific definitions of continental shelves and margins. The first major offshore boundary case of international scope where plate tectonics has constituted a significant argument is the one recently brought before the International Court of Justice by Libya and Tunisia concerning the delimitation of their continental shelves. Of the two parties, Libya placed the greatest emphasis on this concept as a means to determine natural prolongation of its land territory into and under the sea. Tunisia contested Libya's use of the whole of the African continental landmass as a reference unit; in Tunisia's view, considerations of geography, geomorphology, and bathymetry are at least as relevant as are those of geology. In its landmark judgment (February 1982) - which almost certainly will have far-reaching consequences in future such boundary delimitation cases - the court pronounced that It is the outcome, not the evolution in the long-distant past, which is of importance, and that it is the present-day configuration of the coasts and sea bed which are the main factors to be considered, not geology.

Stanley, D.J.

1983-03-01

270

Plate Tectonics  

NSDL National Science Digital Library

Students will go over the main points of plate tectonics, including the theory of continental drift, different types of plate boundaries, seafloor spreading, and convection currents. We have been spending time learning about plate tectonics. We have discussed the theory of continental drift, we have talked about the different types of plate boundaries, we have also learned about seafloor spreading and convection currents. Plate Boundary Diagram Now is your chance ...

Rohlfing, Mrs.

2011-02-03

271

Numerical-perturbation technique for stability of flat-plate boundary layers with suction  

NASA Technical Reports Server (NTRS)

A numerical-perturbation scheme is proposed for determining the stability of flows over plates with suction through a finite number of porous suction strips. The basic flow is calculated as the sum of the Blasius flow and closed-form linearized triple-deck solutions of the flow due to the strips. A perturbation technique is used to determine the increment a(ij) in the complex wavenumber at a given location x(j) due to the presence of a strip centered at x(i). The end result is a set of influence coefficients that can be used to determine the growth rates and amplification factors for any suction levels without repeating the calculations. The numerical-perturbation results are verified by comparison with interacting boundary layers for the case of six strips and the experimental data of Reynolds and Saric for single- and multiple-strip configurations. The influence coefficient form of the solution suggests a scheme for optimizing the strip configuration. The results show that one should concentrate the suction near branch I of the neutral stability curve, a conclusion verified by the experiments.

Reed, H. L.; Nayfeh, A. H.

1986-01-01

272

PBO H2O: Plate Boundary Observatory Studies of the Water Cycle  

NASA Astrophysics Data System (ADS)

The EarthScope Plate Boundary Observatory was built to measure the deformation of the North American continent. PBO stations can also be used to measure ground displacements at much higher frequencies (5-Hz) for studies of fault slip during large earthquakes and for warnings of volcanic eruptions. There is also a long history of using atmospheric delays on the GPS signals to estimate precipitable water vapor (for weather and climate studies) and total electron content (space weather studies). Recently the PBO H2O research group has demonstrated that GPS signals that reflect from the nearby environment can be used for water cycle research. These GPS reflections measure how much water is in the top layer of the soil, how much snow is on its surface, and water content of nearby vegetation. Observing and monitoring spatial and temporal changes in the water cycle is critical for both understanding and predicting Earth's climate. Since GPS reflections encompass an area of ~1000 m^2, they provide a spatial footprint that complements satellite systems which sense much larger areas and in situ systems that sense regions < 1 m^2. Water cycle products are produced from PBO data each day and updated on the PBO H2O website.

Larson, K. M.; Small, E. E.; Chew, C. C.; Nievinski, F. G.; Pratt, J.; McCreight, J. L.; Braun, J.; Boniface, K.; Evans, S. G.

2013-12-01

273

North American plate dynamics  

NASA Technical Reports Server (NTRS)

Deformation within the North American plate in response to various tectonic processes is modeled using an elastic finite element analysis. The tectonic processes considered in the modeling include ridge forces associated with the normal thermal evolution of oceanic lithosphere, shear and normal stresses transmitted across transforms, normal stresses transmitted across convergent boundaries, stresses due to horizontal density contrasts within the continent, and shear tractions applied along the base of the plate. Model stresses are calculated with respect to a lithostatic reference stress state. Shear stresses transmitted across transform boundaries along the San Andreas and Caribbean are small, of the order of 5-10 MPa. Also, compressive stresses of the order of 5-10 MPa transmitted across the major transforms improve the fit to the data. Compressive stresses across convergent margins along the Aleutians and the Middle America trench are important.

Richardson, Randall M.; Reding, Lynn M.

1991-01-01

274

Implementation of a python version of a scaled boundary finite element method for plate bending analysis  

E-print Network

Common finite element programs for plate bending analysis are complicated and limited by the common plate theories. Such programs are usually not user-friendly for designers to implement. Lately, Hou Man et al. from the ...

Chen, Lingfeng, M. Eng. Massachusetts Institute of Technology

2014-01-01

275

The role of positive boundary data in generalized clamped plate equations  

E-print Network

subtle. It depends on the domain and on the particular form of the operator whether there are com unit normal at # # In two dimensions (1) is the clamped plate equation. Here# is the shape of the plate is the deflection of the plate. Most authors concentrated on the Green function G 2,n,# for the Dirichlet prob­ lem

Grunau, Hans-Christoph

276

The interpretation of crustal dynamics data in terms of plate motions and regional deformation near plate boundaries  

NASA Technical Reports Server (NTRS)

The focus of the research was in two broad areas during the most recent 6 month period: the nature and dynamics of time-dependent deformation along major seismic zones, including the influence of irregularities in fault geometry on the earthquake cycles, and the processes contributing to the state of stress and rates of strain in plate interior regions. The principal findings of the research to date are described.

Solomon, Sean C.

1987-01-01

277

Preliminary study for active monitoring of the plate boundary using ACROSS: Synthetic and observed seismic records  

NASA Astrophysics Data System (ADS)

ACROSS (Accurately-Controlled Routinely-Operated Signal System) has been developed for active monitoring of a dynamic state in the Earth's structure (Kumazawa et al., 2000). Since November 2004, we have conducted an array observation of ACROSS signals in Tokai area, central Japan, to identify any seismic reflection (and hopefully its temporal change) from the lower crust and/or subducting Philippine Sea plate (Kasahara et al., 2004). In this report, we show the recent results and discuss the relevance of several arrivals of wave groups to underground structures using the theoretical travel times and synthetic waveforms. The frequency-modulated ACROSS signals (10-20 Hz) have been continuously transmitted from the sources located in Toki city, central Japan (Kunitomo et al., 2005) and received at 22 temporal seismic stations at the offset distance of 40-75 km from the source. We define the transfer function between a source and a receiver as a nine-element second-order tensor, Hjk, where j and k denote directional components of the observed displacement and the excitation force, and r, t and v represent the radial, transverse and vertical components, respectively. We recognized the significant wave groups within the travel time ranges of 10-18 and of 15-23 seconds at 54-74 km offset distance through stacking the data for about 60 days. Such wave groups also appear on the records of a Hi-net station at 57.4km by stacking for 30 days (Yoshida et al., 2004). A 2-D velocity structure model was made for our observation area using seismic exploration records across the central Japan (Iidaka et al., 2003). We calculated both travel times by ray tracing method (Fujie et al., 2000; Kubota et al., 2005), and synthetic seismograms by FDM simulation (Larsen and Schultz, 1995). Comparing the observed time series of Hrr and Hzr to the theoretical travel times and synthetic seismograms, we noticed that the wave groups observed at 61-73 km are well corresponding to the theoretical travel times of reflected waves from the bottom of lower crust Moho (PmP) and from the upper boundary of the Philippine Sea plate (PxP). We believe that these results suggest the potentiality for active monitoring of the subtle changes of geophysical properties in the earth's structure using ACROSS signals in future. Acknowledgements: We appreciate the permission to use the seismic waveform data provided by the Research Group for Seismic Expedition in Central Japan.

Tsuruga, K.; Kasahara, J.; Hasada, Y.; Kunitomo, T.; Ikuta, R.; Watanabe, T.; Yamaoka, K.; Fujii, N.; Kumazawa, M.; Nagao, H.; Nakajima, T.; Saiga, A.; Satomura, M.

2005-12-01

278

The EarthScope Plate Boundary Observatory (PBO) Facility: Innovations, Transformations, and Impact  

NASA Astrophysics Data System (ADS)

The word 'transformation' is not used lightly in science. However, the transformative nature of the EarthScope Plate Boundary Observatory facility on the science community is large and measurable. The impact of the creation, execution and delivery of the PBO resulted in radical changes in the way the geodesy community views permanent, continuously operating (and often) real-time GPS and strain networks, open data policies, and the ability for consortium based facilities, such as UNAVCO, to manage and deliver on large National Science Foundation investments. Our presentation will explore these innovations and transformations from the community, facility, and science perspectives. In the genesis of the EarthScope proposal there was a distinct shift away from the PBO being managed and constructed by prominent PI's within the community to a vesting of the responsibility and authority in UNAVCO to execute on behalf of the entire community. This tipping away from individual PI concerns towards a communal behavior allowed the construction of a facility based on broad input from, and equal access for, any member of the geodesy community. The open and transparent nature of EarthScope, including the open data policy for both facility and PI derived data was truly transformative. One of the key tenants of the PBO was strict adherence to not redesigning unless absolutely necessary. For example PBO monumentation and data processing practices were adopted wholesale from the SCIGN project, while the station selection, project management, permitting practices, data downloading, metadata, and, data communications were refactored for optimum use for the broader geodesy community and to scale with the large geography that confronted PBO. The PBO strainmeter network, one of the largest in the world, started by looking at the procedures of 30 years of heterogeneous installations around the word then crafted, created, and amalgamated new drilling, grouting, installation, and data processing procedures that allowed the project to deal with a compressed installation time line and the varying climactic and geological terrains in the Western US. The science that has come from the PBO deployments includes not only estimates of the secular deformation field across important structures in the active Western US but has provided a full kinematic and dynamic picture of the Pacific and North American Plate boundary interaction. The data registered from the PBO network has been used in diverse studies including determination of the asthenospheric density, temperature, and elastic moduli beneath the Western US (Ito and Simons, 2011), snow depth sensing using GPS multipath (Larson and Nievinski, 2013), continuous monitoring of the horizontal displacement gradient tensor field in Southern California (Holt and Shcherbenko, 2013), and using strainmeter data to constrain the magma reservoir beneath the Yellowstone (Luttrell, 2013). There is little doubt that the EarthScope PBO has met and exceeded its science goals, however what is exciting and transformative is the science that has resulted from the signals and the noise found in between these broad science goals.

Jackson, M. E.; Mencin, D.; Feaux, K.

2013-12-01

279

A 3-D lithospheric model of the Caribbean-South American plate boundary  

NASA Astrophysics Data System (ADS)

A 3-D structural model of the Caribbean-South American plate boundary was constructed by gravity modeling. The model was constrained by four wide-angle seismic refraction sections, Moho depth estimations from receiver functions, and additionally seismological hypocenters, surface geology, and geodynamic information. Density values were calculated from empirical velocity-density functions, and mineralogical-chemical composition considering specific P/T conditions. We tested different structural models for Western and Eastern Venezuela. In the final model, the fit of the measured and modeled gravity fields for a long Caribbean slab in Western Venezuela was better than the fit obtained for a short one. This interpretation is consistent with the constraining data. The slab is interpreted to extend further to the south beneath Northern Colombia and culminates in the area of the seismic cluster of the Bucaramanga nest. The modeling estimates a slab dip angle under Maracaibo and Mérida Andes of 15°, which increases to 32° below 100 km depth. The dip direction of approx. N150°E ± 5 increases lightly eastward. In Eastern Venezuela, considering its short wavelength, lineaments analyzed from gravity data (by curvature methods and Euler deconvolution) seem to be related to shallow structures and density contrast in the Serranía del Interior and not from a deep detached slab beneath the continental crust. It is deduced from modeling results that this slab configuration has a very small influence on the gravity field. The slab was modeled according to the subduction-transform propagation model with purely westward subduction and a slab break off along a vertical dip-slip tear through the lithosphere.

Sanchez, Javier; Götze, Hans-Jürgen; Schmitz, Michael

2011-10-01

280

Noise-based surface wave tomography of the Southern California plate boundary region  

NASA Astrophysics Data System (ADS)

We use ambient noise tomography to investigate the crustal structures of the Southern California plate boundary region with a focus on the San Jacinto Fault Zone. A network consisting of 154 broadband and short period sensors is used to estimate the Green's functions of surface waves propagating between station pairs. To obtain better signal to noise ratios in the noise correlation functions, we adopt a procedure using short time windows (4 hr). Energy tests are performed on the data to remove effects of transient sources and instrumental problems. After computing the correlations functions, we perform Optimal Rotation Algorithm (ORA) calculations (Roux, 2009) to better take into account the unfavorable directive ambient seismic noise that is coming mainly from the Pacific in Southern California. This method is used to make travel time measurements on the vertical, radial and transverse components that can be used to evaluate dispersion using frequency-time analysis for periods between 1-20 seconds. After rejecting paths without sufficient signal to noise ratios, we invert the velocity measurements using the Barmin et al (2001) approach on a 1.5 km grid size. The obtained group velocity maps reveal complex structures with clear velocity contrasts across sections of the San Jacinto fault zone, along with low velocity damage zones and basins. We also find a strong group velocity contrast across the southern part of the San Andreas Fault where the Salton trough produces a slower southwest block. The group velocities are inverted to 3D images of shear wave speeds using the linear inversion method of Hermann and Ammon (2002). The results show flower-type damage structures in the top few km of the crust around the SJFZ that are in agreement with, and complement, earthquake tomography studies in the region.

Zigone, D.; Ben-Zion, Y.; Campillo, M.; Roux, P.

2013-12-01

281

Scalar boundary value problems on junctions of thin rods and plates. I. Asymptotic analysis and error estimates  

E-print Network

We derive asymptotic formulas for the solutions of the mixed boundary value problem for the Poisson equation on the union of a thin cylindrical plate and several thin cylindrical rods. One of the ends of each rod is set into a hole in the plate and the other one is supplied with the Dirichlet condition. The Neumann conditions are imposed on the whole remaining part of the boundary. Elements of the junction are assumed to have contrasting properties so that the small parameter, i.e. the relative thickness, appears in the differential equation, too, while the asymptotic structures crucially depend on the contrastness ratio. Asymptotic error estimates are derived in anisotropic weighted Sobolev norms.

R. Bunoiu; G. Cardone; S. A. Nazarov

2014-03-24

282

Cascadia slow slip events and earthquake initiation theories: Hazards research with Plate Boundary Observatory geodetic data (Invited)  

NASA Astrophysics Data System (ADS)

The relationship of transient slow slip events (SSEs) to great earthquakes is a global focus of intense and critical hazards research. Plate Boundary Observatory (PBO) GPS and borehole strainmeter (BSM) networks in the Cascadia forearc provide detailed data that can be compared with simulations predicting how SSEs might evolve as a great earthquake approaches. Cascadia SSEs represent aseismic slip of a few cm in the direction of plate convergence over a period of days or weeks, in a depth range down-dip from the locked zone expected to generate the next great Cascadia subduction earthquake. During an SSE, shear stress borne in the SSE depth range is transferred up-dip at an above-background loading rate. If shear stress on the locked zone is continually accumulating, the daily probability of reaching a threshold failure stress is elevated during an SSE . Alternatively, if dynamic instability is due to rate-weakening fault strength, then SSEs still promote earthquake initiation, but that initiation may be delayed until after the SSE ends, and short-duration SSEs may have negligible effect. In some numerical simulations, great earthquakes could nucleate in the SSE depth range, where effective pressure is assumed to be low. Certain models predict that successive SSEs will slip to increasingly shallower depths, eventually encountering higher effective stress where shear heating can destabilize slip and lead to dynamic rupture. PBO GPS stations have recorded surface deformation from SSEs since inception in 2003; borehole strainmeters (BSMs) have recorded SSE strain signals since 2007. GPS and seismic tremor data show that SSEs reoccur all along the Cascadia subduction zone. An SSE is in progress somewhere in Cascadia much of the time, so the short-term probability increase warranted by a typical SSE is presumably low. We could, however, detect differences among successive SSEs and use criteria informed by the models described above to judge whether a distinctive SSE might represent a higher short-term earthquake probability increase. In all conceptual models, an SSE with more net slip and/or extending further up-dip is more likely to lead to dynamic rupture. There are also models in which faster propagation speed would promote instability by increasing the potential for shear heating. In northernmost Cascadia, BSMs near the coast, up-dip of SSEs, record transient SSE strains at high signal-to-noise ratio. Successive SSEs have differed somewhat in length and propagation speed, but not greatly in up-dip extent or net slip. BSMs up-dip of northern Oregon SSEs have recorded two large SSEs (in 2011 and 2013) having similar strain time series, as well as tremor patterns. In these regions, BSM data could allow an SSE of greater net slip, shallower up-dip extent, or unusual propagation pattern to be identified. Resolution is poorer in reaches of the forearc with BSMs only down-dip of the SSEs. Up-dip BSMs would also be best-positioned to record strain from aseismic slip approaching the locked zone. Some models predict systematic evolution of SSE behavior as a great earthquake approaches, such as decreasing intervals between SSEs, increasing rupture length and slip speed, and slip at successively shallower depths. The northern Cascadia SSEs observed with BSMs since 2007 have not exhibited these patterns, but PBO geodetic instrumentation provides an opportunity to observe them should they develop.

Roeloffs, E. A.; Beeler, N. M.

2013-12-01

283

Receptivity of Flat-Plate Boundary Layer in a Non-Uniform Free Stream (Vorticity Normal to the Plate)  

NASA Technical Reports Server (NTRS)

Experimental and theoretical studies of low speed leading edge boundary layer receptivity to free-stream vorticity produced by upstream wires normal to the leading edge are discussed. Data include parametric variations in leading edge configuration and details of the incident disturbance field including single and multiple wakes. The induced disturbance amplitude increases with increases in the leading edge diameter and wake interactions. Measurements agree with the theory of M. E. Goldstein.

Kogan, M. N.; Shumilkin, V. G.; Ustinov, M. V.; Zhigulev, S. V.

1999-01-01

284

Numerical modeling of the stabilization of a supersonic flat-plate boundary layer by a porous coating  

Microsoft Academic Search

On the basis of a numerical solution of the two-dimensional Navier-Stokes equations, the stability and the receptivity of\\u000a a supersonic (M? = 6) boundary layer on a flat plate with a passive porous coating partially absorbing flow disturbances is studied. The results\\u000a of direct numerical simulation are in good agreement with the data of the linear stability theory. The studies

I. V. Egorov; V. G. Sudakov; A. V. Fedorov

2006-01-01

285

Using EarthScope Construction of the Plate Boundary Observatory to Provide Locally Based Experiential Education and Outreach  

Microsoft Academic Search

EarthScope is an NSF-funded, national science initiative to explore the structure and evolution of the North American continent and to understand the physical processes controlling earthquakes and volcanoes. This large-scale experiment provides locally based opportunities for education and outreach which engage students at various levels and the public. UNAVCO is responsible for the Plate Boundary Observatory (PBO) component of EarthScope.

M. Jackson; S. Eriksson; K. Barbour; S. Venator; D. Mencin; W. Prescott

2006-01-01

286

Effect of Hall current on MHD mixed convection boundary layer flow over a stretched vertical flat plate  

Microsoft Academic Search

In this paper, the steady magnetohydrodynamic (MHD) mixed convection boundary layer flow of an incompressible, viscous and\\u000a electrically conducting fluid over a stretching vertical flat plate is theoretically investigated with Hall effects taken\\u000a into account. The governing equations are solved numerically using an implicit finite-difference scheme known as the Keller-box\\u000a method. The effects of the magnetic parameter, the Hall parameter

F. M. Ali; R. Nazar; N. M. Arifin; I. Pop

287

Controls on spatial and temporal evolution of prism faulting and relationships to plate boundary slip offshore north-central Sumatra  

NASA Astrophysics Data System (ADS)

and along-strike variations in the morphology and structure of the north-central Sumatran forearc (~1.5°S to 1°N) are broadly coincident with subducting plate topography and an earthquake segment boundary zone below the Batu Islands. We present a detailed interpretation of multichannel streamer seismic reflection data collected offshore north-central Sumatra, to better characterize the morphological and structural variations, provide insight into fault development, and relate structure to plate boundary rupture and seismicity patterns. We interpret two relatively continuous, major fault structures that divide the prism into three strike-parallel belts that can be characterized by the relative fault slip rates along major and minor fault structures. The midslope break fault(s) and upper slope-bounding fault(s) are major, potentially out-of-sequence thrusts accommodating a significant component of the compressional strain. We propose that the upper slope-bounding fault represents the more mature end-member of an evolving fault system. Landward vergent structures are associated with a relatively thin sedimentary section near the deformation front in the center of our study area and suggest a potentially weak shallow plate boundary associated with the subducting Wharton Fossil Ridge.

Cook, Becky J.; Henstock, Timothy J.; McNeill, Lisa C.; Bull, Jonathan M.

2014-07-01

288

Late Neogene geohistory analysis of the Humboldt basin and its relationship to convergence of the Juan de Fuca plate  

USGS Publications Warehouse

Geohistory analysis of Neogene Humboldt basin strata provides important constraints for hypotheses of the tectonic evolution of the southern Cascadia subduction margin, leading up to the arrival of the Mendocino triple junction. This analysis suggests that the tectonic evolution of the Humboldt basin area was dominated by coupling between the downgoing Juan de Fuca plate and the continental margin. This coupling is reflected in the timing of major hiatuses within the basin sedimentary sequence and margin uplift and subsidence which occur during periods of tectonic plate adjustment. -from Author

McCrory, P. A.

1989-01-01

289

Experimental Studies on Wake-Induced Bypass Transition of Flat-Plate Boundary Layers under Favorable and Adverse Pressure Gradients  

NASA Astrophysics Data System (ADS)

This study investigates wake-induced bypass transition of boundary layers on a flat plate which is subjected to favorable and adverse pressure gradients. Inlet free-stream turbulence level is controlled with a turbulence grid. Detailed boundary layer measurements are executed by use of a single hot-wire probe. The main focus of this paper is on how and to what extent the wake-induced bypass transition of a flatplate boundary layer can be affected by favorable - adverse pressure gradient as well as enhanced turbulence intensity. A spoked-wheel-type wake generator creates periodic wakes in front of the flat plate. Two types of the wakes are generated by altering the direction of the movement of the wake-generating bars. Instantaneous velocity signals successfully reveal the flow events associated with the wake passage happening inside the boundary layer, such as the emergence of turbulent spots and calmed regions behind them. Noticeable differences in the transitional behavior due to the wake passage also appear between these two types of the wakes.

Koyabu, Eitaro; Funazaki, Ken-Ichi; Kimura, Manabu

290

The turbulent boundary layer on a porous plate: An experimental study of the heat transfer behavior with adverse pressure gradients  

NASA Technical Reports Server (NTRS)

An experimental investigation of the heat transfer behavior of the near equilibrium transpired turbulent boundary layer with adverse pressure gradient has been carried out. Stanton numbers were measured by an energy balance on electrically heated plates that form the bottom wall of the wind tunnel. Two adverse pressure gradients were studied. Two types of transpiration boundary conditions were investigated. The concept of an equilibrium thermal boundary layer was introduced. It was found that Stanton number as a function of enthalpy thickness Reynolds number is essentially unaffected by adverse pressure gradient with no transpiration. Shear stress, heat flux, and turbulent Prandtl number profiles were computed from mean temperature and velocity profiles. It was concluded that the turbulent Prandtl number is greater than unity in near the wall and decreases continuously to approximately 0.5 at the free stream.

Blackwell, B. F.; Kays, W. M.; Moffat, R. J.

1972-01-01

291

Unsteady Boundary Layer Flow and Heat Transfer of a Casson Fluid past an Oscillating Vertical Plate with Newtonian Heating  

PubMed Central

In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter. PMID:25302782

Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

2014-01-01

292

Unsteady Boundary Layer Flow and Heat Transfer of a Casson Fluid past an Oscillating Vertical Plate with Newtonian Heating.  

PubMed

In this paper, the heat transfer effect on the unsteady boundary layer flow of a Casson fluid past an infinite oscillating vertical plate with Newtonian heating is investigated. The governing equations are transformed to a systems of linear partial differential equations using appropriate non-dimensional variables. The resulting equations are solved analytically by using the Laplace transform method and the expressions for velocity and temperature are obtained. They satisfy all imposed initial and boundary conditions and reduce to some well-known solutions for Newtonian fluids. Numerical results for velocity, temperature, skin friction and Nusselt number are shown in various graphs and discussed for embedded flow parameters. It is found that velocity decreases as Casson parameters increases and thermal boundary layer thickness increases with increasing Newtonian heating parameter. PMID:25302782

Hussanan, Abid; Zuki Salleh, Mohd; Tahar, Razman Mat; Khan, Ilyas

2014-01-01

293

MHD Forced Convective Laminar Boundary Layer Flow from a Convectively Heated Moving Vertical Plate with Radiation and Transpiration Effect  

PubMed Central

A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to whilst the magnetic field and mass transfer velocity are taken to be proportional to where is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

Uddin, Md. Jashim; Khan, Waqar A.; Ismail, A. I. Md.

2013-01-01

294

MHD forced convective laminar boundary layer flow from a convectively heated moving vertical plate with radiation and transpiration effect.  

PubMed

A two-dimensional steady forced convective flow of a Newtonian fluid past a convectively heated permeable vertically moving plate in the presence of a variable magnetic field and radiation effect has been investigated numerically. The plate moves either in assisting or opposing direction to the free stream. The plate and free stream velocities are considered to be proportional to x(m) whilst the magnetic field and mass transfer velocity are taken to be proportional to x((m-1)/2) where x is the distance along the plate from the leading edge of the plate. Instead of using existing similarity transformations, we use a linear group of transformations to transform the governing equations into similarity equations with relevant boundary conditions. Numerical solutions of the similarity equations are presented to show the effects of the controlling parameters on the dimensionless velocity, temperature and concentration profiles as well as on the friction factor, rate of heat and mass transfer. It is found that the rate of heat transfer elevates with the mass transfer velocity, convective heat transfer, Prandtl number, velocity ratio and the magnetic field parameters. It is also found that the rate of mass transfer enhances with the mass transfer velocity, velocity ratio, power law index and the Schmidt number, whilst it suppresses with the magnetic field parameter. Our results are compared with the results existing in the open literature. The comparisons are satisfactory. PMID:23741295

Uddin, Md Jashim; Khan, Waqar A; Ismail, A I Md

2013-01-01

295

Boundary conditions and wall effect for forced convection heat transfer in sintered porous plate channels  

Microsoft Academic Search

Forced convection heat transfer of water and air in plate channels filled with sintered bronze porous media was simulated numerically using a local thermal non-equilibrium model with consideration of the wall effect caused by heat conduction in the plate wall and in the unheated section of the sintered porous media. The numerical model was used to analyze the effects of

Pei-Xue Jiang; Meng Li; Yong-Chang Ma; Ze-Pei Ren

2004-01-01

296

Evolving seismogenic plate boundary megathrust and mega-splay faults in subduction zone (Invited)  

NASA Astrophysics Data System (ADS)

Understanding the fault mechanism and its relationship to the sesimo-tsunamigenesis is a key of the scientific targets of subduction zone and therefore NantroSEIZE project of IODP and future new drilling project of International Ocean Discovery Program keeps focusing on that. Mega-splay fault branched from plate boundary megathrust in subduction zone is located around the border between outer and inner wedges and is considered to cause great earthquake and tsunami such as 1960 Alaska earthquake, 1944 and 1946 Nankai-Tonankai earthquakes, and 2004 Sumatra earthquakes. Seismic reflection studies for the mega-splay fault in 2D and 3D in the Nankai forearc present the reflector with negative or positive polarities with various amplitudes and suggest complicated petrophysical properties and condition of the fault and its surroundings. The Nankai mega-splay fault at a depth of ~5km is going to be drilled and cored by NantroSEIZE experiments and is expected for great progress of understanding of the fault mechanics. Before drilling the really targeted seismogenic fault, we are conducting many exercises of geophysical and geological observations. The core-log-seismic integrated exercise for the exhumed mega-splay fault by drilling was operated for the Nobeoka thrust in the Shimanto Belt, Kyushu, Japan. The Nobeoka thrust was once buried in the depth >~10km and suffered maximum temperature >~300 dgree C. As the core recovery is ~99%, perfect correlation between the core and logging data is possible. Thickness of the fault zone is >200 m with a ~50 cm thick central fault core dividing the phyllitic hanging wall and the footwall of broken-melange like cataclasite. A-few-meter-thick discrete damage zones with fault cores are recognized by difference in physical properties and visual deformation textures at several horizons in the fault zone. Host rocks for those damaged zones are completely lithified cataclasites with abundant mineral veins, which record the older and deeper deformation in the maximum depth >10km. Temperature difference between the hanging wall and footwall suggests the displacement along the Nobeoka thrust is >10km, which is almost similar to the mega-splay fault in the Nankai Trough. Geological and physical properties of the Nobeoka thrust suggest an evolving process of the seismogenic mega-splay fault associated with seismogenic up-thrust of the inner wedge of the accretionary prism.

Kimura, G.; Hamahashi, M.; Fukuchi, R.; Yamaguchi, A.; Kameda, J.; Kitamura, Y.; Hashimoto, Y.; Hamada, Y.; Saito, S.; Kawasaki, R.

2013-12-01

297

The Plate Boundary Observatory: Current status and plans for the next five years  

NASA Astrophysics Data System (ADS)

UNAVCO currently operates and maintains the NSF-funded Plate Boundary Observatory (PBO), which is the geodetic facility of EarthScope. PBO was designed and built from 2003 to 2008 with $100M investment from the NSF Major Research Equipment and Facilities Construction (MREFC) Program. UNAVCO operated and maintained PBO under a Cooperative Agreement (CA) with NSF from 2008 to 2013 and will continue PBO O&M for the next five years as part of the new Geodesy Advancing Geosciences and EarthScope (GAGE) Facility. PBO is largest continuous GPS and borehole geophysical network in the Americas, with 1100 continuous Global Positioning System (cGPS) sites, including several with multiple monuments, 79 boreholes, with 75 tensor strainmeters, 78 short-period, 3-component seismometers, and pore pressure sensors at 23 sites. PBO also includes 26 tiltmeters deployed at volcanoes in Alaska, Mt St Helens, and Yellowstone caldera and 6 long-baseline laser strainmeters. Surface meteorological sensors are collocated at 154 GPS sites. UNAVCO provides high-rate (1 Hz), low-latency (<1 s) GPS data streams (RT-GPS) from 382 stations in PBO. UNAVCO has delivered over 62 Tb of geodetic data to the EarthScope community since its PBO's inception in 2004. Over the past year, data return for the cGPS component of PBO is 98%, well above the data return metric of 85% set by the NSF, a result of efforts to upgrade power systems and communications infrastructure. In addition, PBO has set the standard for the design, construction, and operation of other multi-hazard networks across the Americas, including COCONet in the Caribbean region and TLALOCNet in Mexico. Funding to support ongoing PBO O&M has declined from FY2012 CA levels under the new GAGE Facility. The implications for data return and data quality metrics as well as replacement of aging PBO GPS instruments with GNSS-compatible systems are as yet unknown. A process to assess the cost of specific PBO components, data rates, enhanced capabilities, and method of delivery (i.e. continuous streams vs. archived files) relative to their scientific value will be proposed. In addition, options to partner with other federal mission-oriented agencies and possible commercial ventures also will be discussed. 1100 station PBO continuous GPS Network.

Mattioli, G. S.; Feaux, K.; Meertens, C. M.; Mencin, D.; Miller, M.

2013-12-01

298

Building a Global Data Network for Studies of Earth Processes at the World's Plate Boundaries  

NASA Astrophysics Data System (ADS)

The international geoscience community is engaged in scientifically aligned goals to understand the fundamental processes of crustal formation, modification and destruction at the Earth's plate boundaries through broad multi- disciplinary initiatives such as the InterRidge and InterMARGINS programs. These programs involve the collection of unique data sets during oceanic and terrestrial expeditions and subsequent laboratory work conducted by research institutions around the globe. These international research efforts would benefit significantly if data collections maintained as national efforts could be better linked and broader access were initiated. At present there are no formal agreements within these programs for data sharing between foreign partners. A workshop was convened in May 2007, jointly sponsored and funded by MARGINS, InterMARGINS, InterRidge, Ridge2000, the US National Science Foundation, and the German project "The Future Ocean", to explore current opportunities and challenges for international data exchange to support marine geoscience research broadly. Participants from 14 countries discussed technological, organizational, and cultural issues for building a global data network and agreed on a set of recommendations regarding science user needs, data documentation, data publication, metadata interoperability, and opportunities and obstacles for international data sharing. They underscored that (1) open public access to data is fundamental to verifiable scientific progress; (2) uniform best practices and standards for data acquisition, data submission to data centers, and data publication need to be developed and used routinely within the international community, facilitated by tools that automate metadata acquisition in the field and in the lab; (3) the proliferation of metadata standards needs to be minimized to achieve a uniform approach for scientific metadata building upon the work of existing community-based projects; (4) data centers should expose their data resources via web services to enable data access through programmatic interfaces and expand options for data analysis and visualization; (5) international programs and bodies such as GEOSS, eGY, and ICSU should be leveraged to promote an initiative for a global data network; (6) a dedicated task group is needed to advance the implementation of a global data network along with special interest groups to share experience and solutions on issues concerning metadata and interfaces. Several immediate next steps were identified to initiate the implementation of these recommendations.

Lehnert, K. A.; Carbotte, S.; Tsuboi, S.; Weinrebe, W.

2007-12-01

299

2011 Operations and Maintenance Activities in the East Region of UNAVCO's Plate Boundary Observatory  

NASA Astrophysics Data System (ADS)

2011 marked Year 3 of Operations and Maintenance of the Plate Boundary Observatory (PBO). In the East Region of PBO, it was a year characterized by several major projects as well as scheduled ongoing maintenance activities. The most significant major project was a USGS/ARRA funded communications upgrade in Yellowstone National Park. This upgrade consisted of bringing 8 existing PBO stations within the Yellowstone volcanic region to near real-time communications. This work will be completed on time and in collaboration with the National Park Service. The upgrade promises to provide much faster latency for invaluable data being recorded for one of the most geodetically critical regions of the current PBO network. Another significant ongoing project in the East Region has been supporting the community that continues to use PBO data. In particular, support of Kristine Larson (Univ of CO) both in installing webcams at PBO sites for monitoring snow depth as well as supporting vegetative surveys at current PBO sites. Similarly, the East Region responded promptly to the community with requests for data quality issues that are station hardware related, including replacing GPS antennae and receivers. With regards to ongoing operations and maintenance projects, reasons for site visits in 2011 were dominated by two significant situations: battery replacement and CDMA modem swaps. 83 site visits were required as part of the Operations and Maintenance strategic battery plan of 5 year battery replacements. This proved to be a considerable challenge due to the scale and geography of the scheduled replacements- the sites were spread throughout the entire network, east to west and north to south. 20 station visits were required due to a Verizon upgrade of the older Alltel network purchased by Verizon. These stations are predominantly in the Rocky Mountain region, but often times had limited access to due weather. Overall, despite record snowfalls throughout the west, state of health in the East Region was consistently over 95% operational; a testament to past network-hardening and current vigilance and hard work. The east region looks forward to a successful 2012 campaign.

Dittmann, T.; Feaux, K.; Kasmer, D.; Jenkins, F.; Mencin, D.

2011-12-01

300

The Earthscope Plate Boundary Observatory Alaska Region an Overview of Network Operation, Maintenance and Improvement  

NASA Astrophysics Data System (ADS)

UNAVCO has now completed its third year of operation of the 138 continuous GPS stations, 12 tiltmeters and 31 communications relays that comprise the Alaska Region of the Earthscope Plate Boundary Observatory. Working in Alaska has been challenging due to the extreme environmental conditions encountered and logistics difficulties. Despite these challenges we have been able to complete each summer field season with network operation at 95% or better. Throughout the last three years we have analyzed both our successes and failures to improve the quality of our network and better serve the scientific community. Additionally, we continue to evaluate and deploy new technologies to improve station reliability and add to the data set available from our stations. 2011 was a busy year for the Alaska engineering team and some highlights from last year's maintenance season include the following. This spring we completed testing and deployment of the first Inmarsat BGAN satellite terminal for data telemetry at AC60 Shemya Island. Shemya Island is at the far western end of the Aleutian Islands and is one of the most remote and difficult to access stations in the PBO AK network. Until the installation of the BGAN, this station was offline with no data telemetry for almost one year. Since the installation of the BGAN in early April 2011 dataflow has been uninterrupted. This year we also completed the first deployments of Stardot NetCamSC webcams in the PBO Network. Currently, these are installed and operational at six GPS stations in Alaska, with plans to install several more next season in Alaska. Images from these cameras can be found at the station homepages linked to from the UNAVCO website. In addition to the hard work put in by PBO engineers this year, it is important that we recognize the contributions of our partners. In particular the Alaska Volcano Observatory, the Alaska Earthquake Information Center and others who have provided us with valuable engineering assistance and data telemetry in several locations. With their help we have reduced the number of stations that require manual data download to six in the entire Alaska network getting us closer to our goal of 100% auto data archival for the Alaska network.

Enders, M.; Boyce, E. S.; Bierma, R.; Walker, K.; Feaux, K.

2011-12-01

301

Co-located pore pressure and volumetric strain at Plate Boundary Observatory boreholes  

NASA Astrophysics Data System (ADS)

To establish the viability of pore-pressure instrumentation as a measurement of volumetric deformation in the solid rock matrix, we present initial studies, using Plate Boundary Observatory data, of the relationship between apparent areal strain and pore pressure in the same borehole. The areal strains are given by Gladwin borehole tensor strainmeters (BSM) (and in one case by longbase laser strainmeters). The pore-pressure is measured in a partially sealed, sand-packed region in an uncased section of the borehole containing the BSM. We find parameters relating pore pressure to atmospheric loading and tidal strains. Although these forces explain much of the pressure signal, residual pressures not associated with earthquakes have significant other changes (daily rms signal on the order of 1.5 hPa) attributable to a delay between stress and strain. As this delay becomes large, or even frequency dependent, the degree of coupling between pore-fluid diffusion and elastic parameters in the rock becomes important. We also find that only very small quantities of non-atmospheric and non-tidal strain energy may be explained by pore pressure variation (roughly 0.1 nanostrain/kPa). Passing seismic waves that cause volumetric change also affect the pore pressure. Earthquakes at near and intermediate distances cause a postseismic response that decays withing a few days; this might manifest rapid, short-term changes in permeability by pore-sealing/opening, or changes in fracture-conduit flux, but is likely equilibration of pore-fluid diffusion. Our findings suggest that (1) The pore pressure measurement is stable over hours to weeks. (2) Strainmeters are less sensitive to typical post-seismic transient pressure changes. (3) There may be some level of frequency dependence between the two quantities. A major implication thus follows: Because the pore pressure transducers are apparently stable at long periods and may be more sensitive to fluid-related deformation than strainmeters are, they may be well poised to compliment tectonic deformation studies, assuming site effects may be understood and corrected for - the subject of future work.

Barbour, A.; Agnew, D. C.

2011-12-01

302

Studying the active deformation of distributed plate boundaries by integration of GNSS networks  

NASA Astrophysics Data System (ADS)

In the last decade GNSS networks installed for different purposes have proliferated in Italy and now provide a large amount of data available to geophysical studies. In addition to the existing regional and nation-wide scientific GNSS networks developed by ASI (http://geodaf.mt.asi.it), INGV (http://ring.gm.ingv.it) and OGS (http://crs.inogs.it/frednet), a large number (> 400) of continuously-operating GPS stations have been installed in the framework of regional and national networks, both publicly-operated and commercial, developed to provide real-time positioning capability to surveyors. Although the quality of the data and metadata associated to these stations is generally lower with respect to the "scientific" CGPS stations, the increased density and redundancy in crustal motion information, resulting in more than 500 stations with more than 2.5 years of observations, significantly increase the knowledge of the active deformation of the Italian territory and provides a unique image of the crustal deformation field. The obtained GPS velocity field is analysed and various features ranging from the definition of strain distribution and microplate kinematics within the plate boundary, to the evaluation of tectonic strain accumulation on active faults are presented in this work. Undeforming, aseismic regions (Sardinia, Southern Apulia) provide test sites to evaluate the lower bound on the accuracy achievable to measure tectonic deformation. Integration of GNSS networks significantly improves the resolution of the strain rate field in Central Italy showing that active deformation is concentrated in a narrow belt along the crest of the Apennines, consistently with the distribution of the largest historical and recent earthquakes. Products derived from dense GPS velocity and strain rate fields include map of earthquake potential developed under the assumption that the rate of seismic moment accumulation measured from geodesy distributes into earthquake sizes that follow a truncated Gutenberg-Richter distribution of given b-value and Mmax. The advantage is that, being purely strain-rate based, geodetic models of earthquake potentials require few subjective constraints. In addition, the maps have well-defined error bounds and the approach may apply over regions where poor fault informations are available. This approach provides independent verification of the rates of deformation in regions where geologists have documented faults and allows to evaluate the consistency of the contemporary deformation field and the historical earthquake record. We believe that GNSS networks integration represents an important reality in the framework of the EPOS infrastructure and we strongly support the idea of an European research approach to data sharing among the scientific community.

D'Agostino, Nicola; Avallone, Antonio; Cecere, Gianpaolo; D'Anastasio, Elisabetta

2013-04-01

303

Completion of the 16 station Plate Boundary Observatory (PBO) network on Mt. St. Helens, WA  

NASA Astrophysics Data System (ADS)

The Plate Boundary Observatory (PBO), part of the larger NSF-funded EarthScope project, is completing year 3 of the installation phase of 852 continuously operating GPS stations in the Western United States. Some of these GPS stations are focused specifically on centers of volcanic activity. Mt. St. Helens is one of these volcanic areas of interest in the Pacific Northwest (PNW) region. The PNW region will complete the installation of a 16 station GPS network on Mt. St. Helens during September 2006. This work also includes the co-location and installation of tiltmeters at four of the existing GPS sites. Network upgrades will be completed to handle the increase in data flow from the new GPS stations as well as the data from the tiltmeters and strainmeters. New GPS site installations include six helicopter accessible sites, and three drive to sites on the south flank of the mountain. Higher elevation sites will be outfitted with an eight battery, three solar panel power array to keep the stations operational during winter months. The remaining sites use a four battery, three solar panel array that has proved sufficient at other GPS locations over the past 2 winters. All stations will communicate via one of 2 radio networks set up on the mountain. The northern radio network transmits data for ten stations through a microwave connection at the Johnston Ridge observatory that also provides communications for PBO strainmeter, tiltmeter and CVO equipment. The remaining 10 stations on the south side of the mountain, are relayed through a hub at Washington State University's Vancouver Campus that is also providing data services for CVO. Results from analysis of data from both PBO and USGS GPS stations on the mountain, show a radially inward and downward motion, with the maximum vertical offsets high on the mountain and the maximum horizontal offsets located at distances of 5-10km from the crater. Displacements are small over the 2004-present eruption with a maximum of 3cm of inward movement. Modeling of the data by Lisowski et al. (AGU 2006) only accounts for a volume loss that is one third of the amount of material erupted. GPS stations installed high on the mountain were subjected to severe winter weather and heavy rime ice accumulations over the last year. This ice build-up caused distortion of the GPS antenna phase center, and blocked sun access to the solar panels at several sites. Due to the large battery storage capacity, very few power failures occurred at these stations. However, the build up of ice on the GPS antennas caused cm-level pseudo-displacements that mask the ground movements associated with the eruption.

Austin, K.; Hafner, K.; Fengler, K.; Doelger, S.

2006-12-01

304

The EarthScope Plate Boundary Observatory Response to the 2006 Augustine Alaskan Volcanic Eruption  

NASA Astrophysics Data System (ADS)

During September of 2006, UNAVCO installed five permanent Plate Boundary Observatory (PBO) GPS stations on Augustine Volcano, in the lower Cook Inlet of Alaska. The installations were done at the request of the PBO Magmatic Systems committee in response to the January 11, 2006 eruption of Augustine Volcano. Prior to the eruption, PBO installed five permanent GPS stations on Augustine in 2004. The five existing stations on the volcano were instrumental in detecting precursory deformation of the volcano's flanks prior to and during the eruption. During the course of the first explosive phase of the eruption, two existing PBO stations, AV03 and AV05 were subsequently destroyed by separate pyroclastic flows. The existing station AV04 was heavily damaged by a separate pyroclastic flow during the continuous phase of the eruption and was repaired during September as well. Existing stations AV01 and AV02 were not affected or damaged by the eruption and remained operating during the entire eruptive phase and subsequent debris flows. All five new stations, and maintenance on the three remaining existing stations, were completed by PBO field crews with helicopter support provided by Maritime Helicopters. Lack of roads and drivable trails on the remote volcanic island required that all equipment be transported to each site from an established base camp by slinging gear beneath the helicopter and internal loads. Each new and existing station installed on the volcano consists of a standard short braced GPS monument, two solar panels mounted to an inclined structure, and a six foot high Plaschem enclosure with two solar panels mounted to one of the inclined sides. Each Plaschem houses 24 12 volt batteries that power a Trimble NetRS GPS receiver and one or two Intuicom radios and are recharged by the solar panels. Data from each GPS receiver is telemetered directly or through a repeater radio to a base station located in the town of Homer that transmits the data over the internet to the UNAVCO data archive at ftp://data-out.unavco.or/pub/PBO_rinex where it is made freely available to the public.

Pauk, B.; Feaux, K.; Jackson, M.; Friesen, B.; Enders, M.; Baldwin, A.; Fournier, K.; Marzulla, A.

2006-12-01

305

Investigations of Suction in a Transitional Flat-Plate Boundary Layer  

Microsoft Academic Search

\\u000a For the maintenance of a laminar boundary layer flow on transonic wings, it is necessary to integrate a boundary layer suction\\u000a unit in the nose region. This concept of the Hybrid Laminar Flow control is realized through a suction area adapted to the\\u000a outer pressure distribution by an array of suction holes. With this, a stabilization of the boundary layer

Stefan Becker; Jovan Jovanovic

2010-01-01

306

Active accommodation of plate convergence in Southern Iran: Earthquake locations, triggered aseismic slip, and regional strain rates  

NASA Astrophysics Data System (ADS)

We present a catalog of interferometric synthetic aperture radar (InSAR) constraints on deformation that occurred during earthquake sequences in southern Iran between 1992 and 2011, and explore the implications on the accommodation of large-scale continental convergence between Saudi Arabia and Eurasia within the Zagros Mountains. The Zagros Mountains, a salt-laden fold-and-thrust belt involving ~10 km of sedimentary rocks overlying Precambrian basement rocks, have formed as a result of ongoing continental collision since 10-20 Ma that is currently occurring at a rate of ~3 cm/yr. We first demonstrate that there is a biased misfit in earthquake locations in global catalogs that likely results from neglect of 3-D velocity structure. Previous work involving two M ~ 6 earthquakes with well-recorded aftershocks has shown that the deformation observed with InSAR may represent triggered slip on faults much shallower than the primary earthquake, which likely occurred within the basement rocks (>10 km depth). We explore the hypothesis that most of the deformation observed with InSAR spanning earthquake sequences is also due to shallow, triggered slip above a deeper earthquake, effectively doubling the moment release for each event. We quantify the effects that this extra moment release would have on the discrepancy between seismically and geodetically constrained moment rates in the region, finding that even with the extra triggered fault slip, significant aseismic deformation during the interseismic period is necessary to fully explain the convergence between Eurasia and Saudi Arabia.

Barnhart, William D.; Lohman, Rowena B.; Mellors, Robert J.

2013-10-01

307

North America-Pacific plate boundary, an elastic-plastic megashear - Evidence from very long baseline interferometry  

NASA Technical Reports Server (NTRS)

Data obtained by Mark III VLBI measurements of radio signals from permanent and mobile VLBI sites for 5.5 years of observations, starting in October 1982, were used to derive a picture of the earth crust deformation near the North America-Pacific plate boundary. The data, which included the vector positions of the VLBI sites and their rate of change, were used for comparison with a number of lithospheric deformation models based upon the concept that the motions of points near the North America-Pacific plate boundary are a linear combination of North America and Pacific velocities. The best of these models were found to fit 95 percent of the variance in 139 VLBI length and transverse velocity observations. Instantaneous shear deformation associated with plate tectonics is apparently developing in a zone 450 km wide paralleling the San Andreas Fault; some of this deformation will be recovered through elastic rebound, while the rest will be permanently set through plastic processes. Because the VLBI data have not been collected for a significant fraction of the earthquake cycle, they cannot discriminate between elastic and plastic behaviors.

Ward, Steven N.

1988-01-01

308

Quasi-Love Surface Wave Observations on USArray: Evidence for Upper Mantle Anisotropy Along the North American Plate Boundary  

NASA Astrophysics Data System (ADS)

Strong evidence for mantle anisotropy exists along the North American and Pacific plate boundary, likely a result of deformation of upper-mantle rocks from the applied stress of tectonic motion. We have observed anisotropy-sensitive Love-to-Rayleigh scattered waves, also known as Quasi-Love waves, on the USArray component of EarthScope, on propagation paths that cross the North American plate boundary. These observed Quasi-Love waves may indicate the location and orientation of this anisotropy and help understand the tectonic motion along the North American plate boundary on the Pacific coast of the US. We have performed quantitative and qualitative tests to support the interpretation of these Quasi-Love waves against the misnomer of a surface-reflected body wave or Rayleigh overtone. All of our Quasi-Love wave observations are made after applying a 100 second low-pass to the data in effort to mute higher frequency Rayleigh wave overtones. The Quasi-Love waveforms that we have observed are the largest deviation between the USArray recorded wave trains and long-period synthetic seismograms computed using an isotropic Earth model. The observed amplitudes of the Quasi-Love waves fall roughly within 5-10% of the incident Love wave amplitudes, which is consistent with a 3-5% lateral anisotropic gradient along the great circle path [Yu et al., 1995]. Two example observations that we have made that support the proposed hypothesis are from a 3/31/2006 earthquake source near the Kermadec Islands region, where the observed Quasi-Love wave arrives from the west closely after the arrival of the Love wave, suggesting that the anisotropic scattering occurs relatively close to USArray stations in the Pacific Northwest. By contrast, no Quasi-Love waves are observed from a 4/5/2007 earthquake near the Azores Islands, which arrives at the same stations from the east. A particular point of interest is how the anisotropic scattering mechanism changes, if at all, between the Juan de Fuca subduction zone along the coast of Washington and Oregon and the transform plate boundary in California. Though the exact cause of the anisotropy, whether LPO, parallel fracturing, or a combination of both, may not be known, the orientation of the anisotropy will illuminate the stress and strain in the upper mantle and aid in the investigation of tectonic motion along the boundary.

Rieger, D. M.; Park, J.

2008-12-01

309

Stress in the lithosphere from non-tectonic loads with implications for plate boundary processes  

E-print Network

of the plate material or yield strength profile. In the casematerial by selecting the shape of the lithosphere’s yield strengthmaterial has an elastic-plastic rheology and it has been stressed to its yield strength,

Luttrell, Karen Marie

2010-01-01

310

Plate boundary and major fault system in the overriding plate within the Shumagin gap at the Alaska-Aleutian subduction zone  

NASA Astrophysics Data System (ADS)

Structure in the overriding plate is one of the parameters that may increase the tsunamigenic potential of a subduction zone but also influence the seismogenic behavior and segmentation of great earthquake rupture. The Alaska-Aleutian margin is characterized by along-strike changes in plate interface coupling over relatively small distances. Here, we present trench normal multichannel seismic (MCS) profiles acquired across the Shumagin gap that has not broken in many decades and appears to be weakly coupled. The high fold, deep penetration (636 channel, 8-km long streamer, 6600 cu.in airgun source) MCS data were acquired as part of the ALEUT project. This dataset gives us critical new constraints on the interplate boundary that can be traced over ~100 km distance beneath the forearc with high variation in its reflection response with depth. These profiles also reveal the detailed upper plate fault structure and forearc morphology. Clear reflections in the overriding plate appear to delineate one or more large faults that cross the shelf and the upper slope. These faults are observed 75 km back from the trench and seem to branch at depth and connect to the plate interface within this gap at ~11 s twtt. We compare the reflective structure of these faults to that of the plate boundary and examine where it intersects the megathrust with respect of the expected downdip limit of coupling. We also compare this major structure with the seismicity recorded in this sector. The imaged fault system is associated with a large deep basin (~6s twt) that is an inherited structure formed during the pre-Aleutian period. Basins faults appear to have accommodated primarily normal motion, although folding of sediments near the fault and complicated fault geometries in the shallow section may indicate that this fault has accommodated other types of motion during its history that may reflect the stress-state at the megathrust over time. The deformation within the youngest sediment also suggests also that this fault system might be still active. The coincident wide-angle seismic data coincident with one MCS profile allow the addition of more information about the deep P-wave velocity structure whereas the streamer tomography (Michaelson-Rotermund et al., this session) around the fault system add more detailed view into the complex structure in the shallow portions (upper 2km) of these structures showing a low velocity zone along one large fault suggesting that this fault is still active. These large-scale structures imaged in the overriding plate within the Shumagin gap are probably sufficiently profound to play a major role in the behavior of the megathrust in this area, segmentation of great earthquake rupture area, tsunami generation and may influence the frictional properties of the seismogenic zone at depth.

Becel, A.; Shillington, D. J.; Nedimovic, M. R.; Keranen, K. M.; Li, J.; Webb, S. C.; Kuehn, H.

2013-12-01

311

A exact solution is presented for the cylindrical bending vibration of simply supported function-ally graded plates. Displacement functions that identically satisfy boundary conditions are used to  

E-print Network

-to-thickness ratios. Keywords: Functionally graded material; thick plate; cylindrical bending; vibration. INTRODUCTION in the material. One way to overcome these adverse effects is to use "functionally graded materials" in which function- ally graded plates. Displacement functions that identically satisfy boundary conditions are used

Vel, Senthil

312

Inception of the eastern California shear zone and evolution of the Pacific-North American plate boundary: From kinematics to geodynamics  

Microsoft Academic Search

The San Andreas Fault (SAF) is the transform boundary between the Pacific and the North American plates, yet up to 25% of the relative plate motion is now accommodated by the eastern California shear zone (ECSZ). Here we investigate the inception of the ECSZ and its geodynamic interactions with the SAF using a 3-D viscoelastoplastic finite element model. For a

Mian Liu; Hui Wang; Qingsong Li

2010-01-01

313

Mechanisms for the Origin of Mid-Ocean Ridge Axial Topography: Implications for the Thermal and Mechanical Structure of Accreting Plate Boundaries  

Microsoft Academic Search

To better understand the implications of ridge axis morphology for the thermal and mechanical stmc- ture of accreting plate boundaries, we examine mechanisms for the creation of stress-supported axial to- pography and its dependence on parameters such as spreading rate, asthenosphere viscosity, and plate thickness near the ridge axis. Three basic mechanisms are considered: (1) asthenospheric upwelling in a narrow,

Jason Phipps Morgan; E. M. Parmeotier; J. Lin

1987-01-01

314

Seismic Anisotropy, Deformation, Stress and Faulting in the crust and mantle at the New Zealand Plate Boundary (Invited)  

NASA Astrophysics Data System (ADS)

We summarize measurements of seismic anisotropy and its relation to fault zone structure in the crust and mantle of New Zealand, which sits on the NE/SW striking transpressional boundary region between the Pacific and Australian plates. In the North Island, the Pacific Plate subducts obliquely under the Australian Plate while in the South Island, the Australian plate subducts obliquely under the Pacific Plate. These two subduction zones are joined by the transpressional Alpine Fault. Seismic anisotropy measured with shear wave splitting of SKS and deep teleseismic S arrivals of on-shore stations yield mostly plate-boundary-parallel fast directions (phi) and delay times (dt) ranging on the order of 1.5 to 2.5 seconds, suggesting broad scale shear deformation in the crust, lithosphere and asthenosphere. Asthenospheric shear may be considered as trench-parallel flow below the North Island. Delay times are even higher (up to 4.5 s) in the back-arc Central Volcanic Region (CVR), an area of active extension, and decrease sharply to zero at its western boundary. These values have been interpreted as caused by melt bands in the CVR giving way to a region that has been stripped of lithosphere. South of the CVR the back-arc is in compression and splitting is nearly constant at 1.6 s, except for higher delay times up to 3 s in the southeastern North Island. Abrupt lateral changes in delay time in the North Island have been attributed to strong, shallow anisotropy in the crust and mantle wedge, but some contamination from isotropic velocity changes may also affect the delay times. An ocean bottom seismometer (OBS) deployment off the South Island shows that plate-boundary parallel anisotropy, interpreted as the limit of shear deformation, reaches to 100 km on either side of the Alpine Fault, changing to nearly E-W at the eastern-most land stations and at most of the offshore east coast stations. Southern OBS and land stations yield more northerly fast directions, suggesting rotation of anisotropic axes and either alignment with asthenospheric flow parallel to the absolute plate motion, or small strain at an angle of about 45 degrees to the shear plane. Frequency-dependence of delay times is apparent for teleseismic S, ScS and local S phases, with smaller periods yielding smaller delay times. The higher frequency waves also yield more scatter in delay times as well as fast directions. However, spatial averaging and delay time tomography of local S phases yield consistent results, with regions of high anisotropy near known fault zones and fault-zone parallel anisotropy in many areas, suggesting fault zone mineralization or shearing near the fault zone controls some anisotropy. In many other areas, shear wave splitting of local earthquakes is parallel to the maximum horizontal stress direction (SHmax) as measured by focal mechanism inversions, suggesting that aligned, fluid-filled cracks control anisotropy in the shallow crust away from faults. For aftershocks of the E-W striking 2010 M=7.1 Darfield earthquake in the Canterbury Plains in the east-central South Island, a spatial rotation of both fast directions and SHmax occurs. Far from the fault plane, SHmax and phi are at 116+-18 degrees, but earthquakes increasingly near to the fault trace yield increasingly E-W SHmax. This suggests the fault is either weak, or the stress rotated after the earthquake.

Savage, M. K.; Karalliyadda, S.; Zietlow, D. W.; Holt, R. A.; Sheehan, A. F.; Townend, J.; Stern, T. A.

2013-12-01

315

0.1 1 10 100 Subduction at convergent plate boundaries provides a mechanism for recycling fluid-  

E-print Network

submerged in 7 mL 25 mM NaOH trap solution · Ice bath around trap to promote halogen dissolution Halogen (I) · 10 samples analyzed for F + Cl by NaOH fusion, followed by IC, yielded similar results & crushed sample + 0.5 g V2O5 accelerator in SiO2 boat · 0/8 Lmin-1 wet O2 flow · 1100°C furnace temp

316

Seismic velocity structures in the southern California plate-boundary environment from double-difference tomography  

NASA Astrophysics Data System (ADS)

We present tomographic images of crustal structures in the southern California plate-boundary area, with a focus on the San Jacinto fault zone (SJFZ), based on double-difference inversions of earthquake arrival times. Absolute arrival times of 247 472 P and 105 448 S wave phase picks for 5493 earthquakes recorded at 139 stations in southern California are used. Starting with a layered 1-D model, and continuing in later iterations with various updated initial models, we invert the data for Vp and Vs in a 270 km long, 105 km wide and 35 km deep volume around the SJFZ using a spatially variable grid with higher density around the SJFZ. The examined volume stretches from Cajon Pass to the northernmost Imperial Fault Zone and includes portions of the southern San Andreas Fault (SAF), the Elsinore Fault and the Brawley Seismic Zone in the Salton Trough. Because differential traveltimes used in the double-difference inversions are most sensitive to near-source structures, we obtain high resolution around the earthquake sources. After 30 iterations we improve the average traveltime misfit by a factor of 16. Though ray coverage is limited at shallow depths, we obtain detailed images of seismic velocities from 3 to 20 km throughout much of the study area. Our final velocity results show zones of low-velocity and anomalous Vp/Vs ratios associated with various fault strands and sedimentary basins, along with clear velocity contrasts across the SJFZ and the southern SAF. The velocity reductions in fault zone regions are generally highest in geometrically complex areas (up to 30-50 per cent in the top few kilometres), are higher for Vs than for Vp, and follow a flower-type pattern with depth. In the central section of the SJFZ, from the San Jacinto valley to the trifurcation area, the northeast side of the fault has generally higher seismic velocities than the southwest block. The obtained contrasts of Vp are more persistent and higher (up to 20 per cent) than the contrasts of Vs (up to 15 per cent), although the differences may stem (at least partially) from the higher resolution of Vp images. In the SJFZ sections to the northwest and southeast, there are patches with reversed velocities contrasts especially in the shallow crust near the San Jacinto Valley and other basins. Along the Banning fault there is no clear velocity contrast. For the southern SAF, the northeast side has generally lower seismic velocities in the seismogenic zone with patches of contrast reversals in the shallow crust. In the Brawley Seismic Zone, the northeast side has somewhat lower velocities in the ˜20 km section near the southern SAF and higher velocities farther to the southwest. The imaged features have important implications for various aspects of earthquake and crustal dynamics in the region.

Allam, A. A.; Ben-Zion, Y.

2012-08-01

317

Crustal structure of a transform plate boundary: San Francisco Bay and the central California continental margin  

USGS Publications Warehouse

Wide-angle seismic data collected during the Bay Area Seismic Imaging Experiment provide new glimpses of the deep structure of the San Francisco Bay Area Block and across the offshore continental margin. San Francisco Bay is underlain by a veneer (<300 m) of sediments, beneath which P wave velocities increase rapidly from 5.2 km/s to 6.0 km/s at 7 km depth, consistent with rocks of the Franciscan subduction assemblage. The base of the Franciscan at-15-18 km depth is marked by a strong wide-angle reflector, beneath which lies an 8- to 10-km-thick lower crust with an average velocity of 6.75??0.15 km/s. The lower crust of the Bay Area Block may be oceanic in origin, but its structure and reflectivity indicate that it has been modified by shearing and/or magmatic intrusion. Wide-angle reflections define two layers within the lower crust, with velocities of 6.4-6.6 km/s and 6.9-7.3 km/s. Prominent subhorizontal reflectivity observed at near-vertical incidence resides principally in the lowermost layer, the top of which corresponds to the "6-s reflector" of Brocher et al. [1994]. Rheological modeling suggests that the lower crust beneath the 6-s reflector is the weakest part of the lithosphere; the horizontal shear zone suggested by Furlong et al. [1989] to link the San Andreas and Hayward/Calaveras fault systems may actually be a broad zone of shear deformation occupying the lowermost crust. A transect across the continental margin from the paleotrench to the Hayward fault shows a deep crustal structure that is more complex than previously realized. Strong lateral variability in seismic velocity and wide-angle reflectivity suggests that crustal composition changes across major transcurrent fault systems. Pacific oceanic crust extends 40-50 km landward of the paleotrench but, contrary to prior models, probably does not continue beneath the Salinian Block, a Cretaceous arc complex that lies west of the San Andreas fault in the Bay Area. The thickness (10 km) and high lower-crustal velocity of Pacific oceanic crust suggest that it was underplated by magmatism associated with the nearby Pioneer seamount. The Salinian Block consists of a 15-km-thick layer of velocity 6.0-6.2 km/s overlying a 5-km-thick, high-velocity (7.0 km/s) lower crust that may be oceanic crust, Cretaceous arc-derived lower crust, or a magmatically underplated layer. The strong structural variability across the margin attests to the activity of strike-slip faulting prior to and during development of the transcurrent Pacific/North American plate boundary around 29 Ma. Copyright 1996 by the American Geophysical Union.

Holbrook, W. S.; Brocher, T. M.; Ten, Brink, U. S.; Hole, J. A.

1996-01-01

318

Coupled effects of director orientations and boundary conditions on light induced bending of monodomain nematic liquid crystalline polymer plates  

NASA Astrophysics Data System (ADS)

A photo-chromic liquid crystal polymers (LCPs) is a smart material for large light-activated variation or bending to transfer luminous energy into mechanical energy. We study the light induced behavior by modeling planar and homeotropic nematic network polymer plates. We effectively illustrate some reported experimental outcomes and theoretically predict some possible bending patterns. This paper constructs an understanding between the bending behaviors and interactions among the alignments, aspect ratios and boundary conditions, etc. Our work provides information on optimizing light induced bending in the process of micro-opto-mechanical system (MOMS) design.

You, Yue; Xu, Changwei; Ding, Shurong; Huo, Yongzhong

2012-12-01

319

Scalings for unsteady natural convection boundary layers on an evenly heated plate with time-dependent heating flux  

NASA Astrophysics Data System (ADS)

It is of fundamental significance, especially with regard to application, to fully understand the flow behavior of unsteady natural convection boundary layers on a vertical plate heated by a time-dependent heat flux. Such an understanding is currently scarce. In this paper, the scaling analysis by Lin et al. [Phys. Rev. E 79, 066313 (2009), 10.1103/PhysRevE.79.066313] using a simple three-region structure for the unsteady natural convection boundary layer of a homogeneous Newtonian fluid with Pr >1 under isothermal heating was substantially extended for the case when the heating is due to a time-varying sinusoidal heat flux. A series of scalings was developed for the thermal boundary thickness, the plate temperature, the viscous boundary thicknesses, and the maximum vertical velocity within the boundary layer, which are the major parameters representing the flow behavior, in terms of the governing parameters of the flow, i.e., the Rayleigh number Ra, the Prandtl number Pr, and the dimensionless natural frequency fn of the time-varying sinusoidal heat flux, at the start-up stage, at the transition time scale which represents the ending of the start-up stage and the beginning of the transitional stage of the boundary-layer development, and at the quasi-steady stage. These scalings were validated by comparison to 10 full numerical solutions of the governing equations with Ra, Pr, and fn in the ranges 106?Ra?109, 3?Pr?100, and 0.01?fn?0.1 and were shown in general to provide an accurate description of the flow at different development stages, except for high-Pr runs in which a further, although weak, Pr dependence is present, which cannot be accurately predicted by the current scaling analysis using the simple three-region structure, attributed to the non-boundary-layer nature of the velocity field with high-Pr fluids. Some scalings at the transition time scale and at the quasi-steady stage also produce noticeable deviations from the numerical results when fn is reduced, indicating that there may be a further fn dependence of the scalings which also cannot be accurately predicted by the current scaling analysis.

Lin, Wenxian; Armfield, S. W.

2013-12-01

320

Scalings for unsteady natural convection boundary layers on an evenly heated plate with time-dependent heating flux.  

PubMed

It is of fundamental significance, especially with regard to application, to fully understand the flow behavior of unsteady natural convection boundary layers on a vertical plate heated by a time-dependent heat flux. Such an understanding is currently scarce. In this paper, the scaling analysis by Lin et al. [Phys. Rev. E 79, 066313 (2009)] using a simple three-region structure for the unsteady natural convection boundary layer of a homogeneous Newtonian fluid with Pr>1 under isothermal heating was substantially extended for the case when the heating is due to a time-varying sinusoidal heat flux. A series of scalings was developed for the thermal boundary thickness, the plate temperature, the viscous boundary thicknesses, and the maximum vertical velocity within the boundary layer, which are the major parameters representing the flow behavior, in terms of the governing parameters of the flow, i.e., the Rayleigh number Ra, the Prandtl number Pr, and the dimensionless natural frequency f(n) of the time-varying sinusoidal heat flux, at the start-up stage, at the transition time scale which represents the ending of the start-up stage and the beginning of the transitional stage of the boundary-layer development, and at the quasi-steady stage. These scalings were validated by comparison to 10 full numerical solutions of the governing equations with Ra, Pr, and f(n) in the ranges 10(6)?Ra?10(9), 3?Pr?100, and 0.01?f_{n}?0.1 and were shown in general to provide an accurate description of the flow at different development stages, except for high-Pr runs in which a further, although weak, Pr dependence is present, which cannot be accurately predicted by the current scaling analysis using the simple three-region structure, attributed to the non-boundary-layer nature of the velocity field with high-Pr fluids. Some scalings at the transition time scale and at the quasi-steady stage also produce noticeable deviations from the numerical results when f(n) is reduced, indicating that there may be a further f(n) dependence of the scalings which also cannot be accurately predicted by the current scaling analysis. PMID:24483563

Lin, Wenxian; Armfield, S W

2013-12-01

321

Upper mantle structure beneath the Caribbean-South American plate boundary from surface wave tomography  

Microsoft Academic Search

We have measured shear wave velocity structure of the crust and upper mantle of the Caribbean-South American boundary region by analysis of fundamental mode Rayleigh waves in the 20- to 100-s period band recorded at the BOLIVAR\\/GEODINOS stations from 2003 to 2005. The model shows lateral variations that primarily correspond to tectonic provinces and boundaries. A clear linear velocity change

Meghan S. Miller; Alan Levander; Fenglin Niu; Aibing Li

2009-01-01

322

ELSEVIER Tectonophysics 293 (1998) 225238 Plate boundary deformation between the Pacific and North America in  

E-print Network

Fuca Ridge and the Cascadia subduction zone resulted in ridge fragmentation in the Explorer region to resolve these issues. Here, the interaction of the Juan de Fuca Ridge and the Cascadia subduction zone has of the consequences of plate tectonics is that a spreading ridge will eventually approach a subduction zone

323

The Plate Boundary Observatory Cascadia Network: Development and Installation of a Large Scale Real-time GPS Network  

NASA Astrophysics Data System (ADS)

The EarthScope Plate Boundary Observatory (PBO), through a NSF-ARRA supplement, has enhanced the geophysical infrastructure in in the Pacific Northwest by upgrading 232 Plate Boundary Observatory GPS stations to allow the collection and distribution of high-rate (1 Hz), low-latency (<1 s) data streams (RT-GPS). These upgraded stations supplemented the original 100 RT-GPS stations in the PBO GPS network. The addition of the new RT-GPS sites in the Pacific Northwest should spur new volcano and earthquake research opportunities in an area of great scientific interest and high geophysical hazard. Streaming RT-GPS data will enable researchers to detect and investigate strong ground motion during large geophysical events, including a possible plate-interface earthquake, which has implications for earthquake hazard mitigation. A total of 282 PBO stations were upgraded and added to the UNAVCO real-time GPS system, along with addition of 22 new meteorological instruments to existing PBO stations. Extensive testing of BGAN satellite communications systems has been conducted to support the Cascadia RT-GPS upgrades and the installation of three BGAN satellite fail over systems along the Cascadia margin will allow for the continuation of data flow in the event of a loss of primary communications during in a large geophysical event or other interruptions in commercial cellular networks. In summary, with these additional upgrades in the Cascadia region, the PBO RT-GPS network will increase to 420 stations. Upgrades to UNAVCO's data infrastructure included evaluation and purchase of the Trimble Pivot Platform, servers, and additional hardware for archiving the high rate data. UNAVCO staff is working closely with the UNAVCO community to develop data standards, protocols, and a science plan for the use of RT-GPS data.

Austin, K. E.; Blume, F.; Berglund, H. T.; Dittman, T.; Feaux, K.; Gallaher, W. W.; Mattioli, G. S.; Mencin, D.; Walls, C. P.

2013-12-01

324

Combined regional gravity model of the Andean convergent subduction zone and its application to lithospheric modelling in active plate margins  

NASA Astrophysics Data System (ADS)

Comparison of global GOCE gravity models with terrestrial gravity data reveals large systematic differences in South America, which can be attributed to a low data quality of the terrestrial data. Correspondingly, these large inconsistencies are also reflected when comparing GOCE models with pre-GOCE combined global models such as EGM2008. Therefore, it could be assumed that lithospheric models of the study region, which did not yet include GOCE, are also affected with long to medium wavelength errors. In a joint effort of geodesy and geophysics, a regional gravity field model for the Andean convergent subduction zone is computed as a combination of satellite gravity data from GOCE and GRACE, terrestrial gravity data of the study region, as well as satellite altimetry in the adjacent Pacific ocean. In a first step, the ground data (gravity anomalies and associated heights) are validated against external information, such as global GOCE gravity models (within the limited spectral band captured by the global models), and ACE2 digital terrain model regarding the height information attached to the terrestrial gravity data base. For the validation of ground gravity data, the high-frequency signal content (mainly contained in terrestrial data) is reduced consistently by a topographic-isostatic reduction. The optimum combination of terrestrial gravity anomalies and GOCE satellite gravity is achieved by Least Squares Collocation, taking - as much as possible - error information of the input data into account. Also the omission error related to non-resolved high-frequency gravity signal of the satellite data is considered adequately. As a result, not only a combined regional gravity field model, but also associated error information is derived. The resulting model is validated against external gravity data and also regarding plausibility of geophysical interpretation. Finally, lithospheric density modelling applying the IGMAS+ software is performed based on this new gravity field model, and the resulting density model is compared to a model of the pre-GOCE area, thus evaluating the impact of GOCE on geophysical modelling of the lithosphere. It will be shown that artefacts in EGM2008 could be identified and eliminated especially in regions with no or very poor terrestrial data. Therefore, we conclude that with this regional gravity field model large-to medium-scale lithospheric modelling of the whole Andes region has now become possible.

Pail, Roland; Hosse, Michael; Horwath, Martin; Gutknecht, Ben; Holzrichter, Nils

2014-05-01

325

Thermochronology and tectonics of the Leeward Antilles: Evolution of the southern Caribbean Plate boundary zone  

Microsoft Academic Search

Tectonic reconstructions of the Caribbean Plate are severely hampered by a paucity of geochronologic and exhumation constraints from anastomosed basement blocks along its southern margin. New U\\/Pb, 40Ar\\/39Ar, apatite fission track, and apatite (U-Th)\\/He data constrain quantitative thermal and exhumation histories, which have been used to propose a model for the tectonic evolution of the emergent parts of the Bonaire

Roelant van der Lelij; Richard A. Spikings; Andrew C. Kerr; Alexandre Kounov; Michael Cosca; David Chew; Diego Villagomez

2010-01-01

326

Boundary layer receptivity to free-stream sound on elliptic leading edges of flat plates  

NASA Astrophysics Data System (ADS)

The leading-edge receptivity to acoustic waves of two-dimensional bodies is investigated using a spatial solution of the Navier Stokes equations in vorticity/stream function form in general curvilinear coordinates. The free stream is composed of a uniform flow with a superposed periodic velocity fluctuation of small amplitude. The method follows that of Haddad & Corke (1998), in which the solution for the basic flow and the linearized perturbation flow are solved separately. The initial motivation for the work comes from past physical experiments for flat plates with elliptic leading edges, which indicated narrow frequency bands of higher neutral-curve Branch I receptivity. We investigate the same conditions in our simulations, as well as on a parabolic leading edge. The results document the importance of the leading edge, junction between the ellipse and flat plate, and pressure gradient to the receptivity coefficient at Branch I. Comparisons to the past experiments and other numerical simulations showed the influence of the elliptic leading-edge/flat-plate joint as an additional site of receptivity which, along with the leading edge, provides a wavelength selection mechanism which favours certain frequencies through linear superposition.

Wanderley, Juan B. V.; Corke, Thomas C.

2001-02-01

327

Characteristics of a turbulent natural convection boundary layer along a vertical flat plate  

Microsoft Academic Search

The present hot-wire measurements of a turbulent natural convection boundary layer give attention to the quantitatively unclarified features of the near-wall region, in order to ascertain the heat transfer rate and wall shear stress on the basis of mean temperature and mean velocity profiles via theoretical considerations. In addition to yielding results that illuminate the conventional analogy between heat and

T. Tsuji; Y. Nagano

1988-01-01

328

Effect of two-scale roughness on boundary layer transition over a heated flat plate  

Microsoft Academic Search

Roughness can have a significant impact on turbine performance through increased profile losses from aerodynamic drag and increased internal blade cooling requirements resulting from external heat transfer enhancement. Transitional flow boundary layers have been shown to exist over turbine blades for various operating conditions. Although the turbine blade roughness is nonuniform and three-dimensional, not much work has been done to

Mark William Pinson

1998-01-01

329

Effects of Plate Boundary Migration on Mantle Dynamics of Oceanic Triple Junctions  

NASA Astrophysics Data System (ADS)

This study investigates characteristics of mantle flow, thermal structure, and melting around an oceanic ridge-ridge-ridge (RRR) triple junction. RRR triple junctions mark the location of unique upwelling conditions along the global mid-ocean ridge system, and mantle dynamics are predicted to be significantly different than the case where only two plates diverge. An earlier study (Georgen and Lin, EPSL 2002) focused on predicting mantle flow and temperature patterns around a triple junction with geometry similar to the Rodrigues Triple Junction in the central Indian Ocean. The Rodrigues Triple Junction is comprised of the ultra-slow-spreading Southwest Indian Ridge and the intermediate-spreading Central and Southeast Indian ridges. Using a three-dimensional finite element model, Georgen and Lin suggested the following results: (1) The upwelling velocity and temperature along the slowest-spreading branch were calculated to increase toward the triple junction, approaching the greater upwelling rate and higher temperature of the fastest-spreading Southeast Indian Ridge branch. In contrast, the velocity and thermal fields for the fastest-spreading ridge were not significantly different from the case of a single ridge with the corresponding spreading rate. (2) Upwelling velocity along the Southwest Indian Ridge was predicted to increase more than threefold within 200 km of the triple junction. A strong component of along-axis flow, directed away from the triple junction, was also predicted, as were temperature increases of approximately 75oC at depths within the partial melting zone. The investigation of Georgen and Lin (2002) fixed the triple junction point in the middle of the model domain, driving mantle flow by the divergence of three surface plates. In this sense, it was a relative plate motion study. However, triple junctions migrate with respect to the absolute plate motion reference frame, and this migration adds an additional component of flow to the three-dimensional nature of upwelling. This study incorporates triple junction migration into a three-dimensional finite element numerical model, and contrasts new model predictions with the earlier results derived with the triple junction fixed to the absolute plate motion reference frame. We also comment on the implications of triple junction migration for the melting history of mantle parcels cycled through the triple junction system.

Georgen, J.

2005-12-01

330

Deformation record of 4-d accommodation of strain in the transition from transform to oblique convergent plate margin, southern Alaska (Invited)  

NASA Astrophysics Data System (ADS)

Crustal deformation at the transition from a dextral transform to subduction in the northern Cordillera is complicated by both the bend of the margin and the presence of low-angle subduction of an oceanic plateau, the Yakutat microplate, into the 'corner'. The dextral Denali Fault system located ~400 km inboard of the plate margin shows a similar transition from a dominantly strike-slip to transpressional regime as it curves to the west. Thermochronologic and structural studies in both areas indicate crustal response through the transition region is highly varied along and across strike. Previous thermochronology along the Fairweather fault SE of the St. Elias bend shows the most rapid exhumation occurs in close proximity to the fault, decreasing rapidly away from it. Enkelmann et al. (2010) and more recent detrital zircon FT (Falkowski et al., 2013 AGU abstract) show rapid and deep exhumation concentrated in the syntaxis, but over a fairly broad area continuing north beyond the Fairweather fault. Although the region is dominantly under ice, borders of the rapidly exhuming region appear to be previously identified major high-angle faults. This suggests that structures controlling the extreme exhumation may have significant oblique slip component, or, if flower structure, are reverse faults, and the region may be exhuming by transpression, with a significant component of pure shear. Southwest of the syntaxis, where convergence dominates over strike-slip, thin-skinned fold-and-thrust belts in the Yakutat microplate strata account for the shortening. The long-term record of convergence in this area is more cryptic due to sediment recycling through deep underplating and/or limited exhumation by upper crustal shortening, but a wide range of thermochronologic studies suggests that initial exhumation in the region began ~ 30 Ma and most rapid exhumation in the syntaxis began ~ 5 Ma. In the eastern Alaska Range a significant component of strike-slip, in addition to convergence, has been accommodated along the Denali Fault since E. Miocene. Southeast of the bend there is little evidence of convergence across the fault and Quaternary slip is ~12-13.5 mm/year. The eastern restraining bend of the Denali fault is much broader than the syntaxis and dextral slip continues at rates of ~10 mm/year, but the rock response to increasing obliquity is similar. Low and moderate-T cooling histories determined from a wide range of isotopic systems on minerals from bedrock show exhumation strongly localized on the north side of the high-angle Denali fault, south of the Hines Creek fault, since ~25 Ma. The structural record in ductilely deformed rocks from the most highly exhumed regions shows transpressive deformation over a few km wide region, but above the brittle-ductile transition strain becomes highly partitioned and is accommodated by thrust and normal faults on the north side of the bend. A connector fault between the Fairweather and Totschunda-Denali fault systems has been speculated on but it is not clear whether a single through-going fault is expressed at the surface. Any connector is likely a relatively young structure compared to the Fairweather and Denali systems' histories of long-lived oblique convergence. Overall, in both regions high-angle faults appear to be critical for controlling the location of major deep-seated and/or long-lived exhumation, and deformation at these geometrical complexities is dominated by transpression.

Roeske, S.; Benowitz, J.; Enkelmann, E.; Pavlis, T. L.

2013-12-01

331

Evolutionary process of Beppu Bay in central Kyushu, Japan: a quantitative study of the basin-forming process controlled by plate convergence modes  

NASA Astrophysics Data System (ADS)

This integrated tectonic study reveals the basin-forming and deforming processes on an active margin. Southwest Japan (SWJ) is an island arc under the influence of oblique subduction of the Philippine Sea plate, which has provoked dextral slips on the arc-bisecting Median Tectonic Line (MTL). Plio-/Pleistocene sediments in Beppu Bay, a tectonic depression at the westernmost portion of the MTL, are categorized into lower (5 ~ 0.7 Ma), upper (0.7 ~ 0.3 Ma), and an auxiliary uppermost (0.3 Ma ~ present) unit in ascending order. Detailed seismic interpretation demonstrates that major structures in the deep interior of the basin are an older half-graben under a strong N-S extensional regime and a younger pull-apart sag that developed in a right-stepping part of the MTL as a result of late Quaternary-enhanced strike-slip rates on the fault. Sediments within the pull-apart have been deformed by later inversion events as a contraction phase arose. Conspicuous deformation of the hanging wall of the low-angle detachment of the basin was successfully reproduced by numerical modeling. Based on a discrete element method, this suggests that structural differences in the deformed sedimentary layers are caused by differences in the dip angles of the faults. Remarkable temporal changes in tectonic regimes around Beppu Bay and other areas of SWJ are probably related to transient modes of convergence, including the migration of the Euler pole, of the Philippine Sea plate since ca. 6 Ma.

Itoh, Yasuto; Kusumoto, Shigekazu; Takemura, Keiji

2014-12-01

332

Transients in Pacific/North American Plate Boundary Deformation: Synthesis and Modeling of GPS and Borehole Strain Observations  

NASA Technical Reports Server (NTRS)

This is the Final Technical Report on research conducted between 1 June 1997 and 14 September 2001 entitled "Transients in Pacific/North American plate boundary deformation: Synthesis and modeling of GPS and borehole strain observations." As the project title implies, our effort involved a geodetic study of strain transients, i.e., temporal variations in deformation rates, that occur within plate boundary zones and their relationship to earthquakes and plate motions. Important transients occur during and following large earthquakes, and there are also strain transients not apparently associated with earthquakes. A particularly intriguing class of transients, for which there is a modest but growing list of examples, are preseismic anomalies. Such earthquake precursors, if further documented and understood, would have obvious importance for earthquake hazard mitigation. Because the timescales for these diverse transients range over at least 6 orders of magnitude (minutes to years), no single geodetic technique is optimum. We therefore undertook a systematic synthesis of Global Positioning Satellite (GPS) and borehole strainmeter data in three areas in California where there are adequate numbers of both types of instruments (or their equivalent): the San Francisco Bay region (within the Bay Area Regional Deformation network), southern California (within the Southern California Integrated GPS Network), and Parkfield (where a two-color laser system provides a proxy for continuous GPS measurements). An integral component of our study was the elucidation of the physical mechanisms by which such transients occur and propagate. We therefore initiated the development of multiple forward models, using two independent approaches. In the first, we explored the response to specified earthquake slip in viscoelastic models that incorporated failure criteria and the geometry of major faults in California. In the second approach, we examined the dynamical response of a complex rheological medium to the application of a far-field stress imposed by plate motions. The forward models were used both to gain insight into the range of strain transients to be expected under different assumed mechanical conditions and to develop representations for strain fields that allow GPS, borehole, and other strain data to be combined in a self-consistent, yet well-determined, manner. The models also provided a basis for hypothesis testing, by which data from a strain transient well characterized by GPS and borehole observations were utilized to distinguish among competing candidates for the causative physical mechanism and the governing physical characteristics. During the three years of this project, continued to a fourth year through a no-cost extension of the grant, we published 14 papers and presented or co-authored 37 papers at national scientific meetings.

Solomon, Sean C.; Frey, H. V. (Technical Monitor)

2002-01-01

333

Evolution of three-dimensional coherent structures in a flat-plate boundary layer  

Microsoft Academic Search

Using a data base generated by a numerical simulation, the three-dimensional coherent structures of a transitional, spatially evolving boundary layer are determined and their spatio-temporal behavior is investigated in detail. The coherent structures are calculated by the proper orthogonal decomposition method (POD), which leads to an expansion of the flow field variables into Karhunen-Loeve eigenfunctions. It is shown that the

Dietmar Rempfer; Hermann F. Fasel

1994-01-01

334

An experimental and theoretical investigation of instabilities in hypersonic flat plate boundary layer flow  

Microsoft Academic Search

As part of an investigation on hypersonic boundary layer transition, the first successful instantaneous hot-wire and fluctuating pressure measurements have been conducted in the Ludwieg-tube facility of DLR at a free-stream Mach number of M?=5. The disturbance amplitudes [root-mean-square (RMS) values] of the fluctuations of Pitot pressure and mass flow are smaller than the values measured in conventional, i.e., continuously

Volker Wendt; Martin Simen; Ardeshir Hanifi

1995-01-01

335

Crustal Buoyancies Dominate over Plate Boundary Effects in the U.S. Basin and Range: The Requirement of Weak Faults  

NASA Astrophysics Data System (ADS)

We model the long-term dynamics of the seismogenic layer within the plate boundary zone of western North America, where the relevant time scale is 105 -- 106 years. We utilize a forward dynamic modeling approach, where the body force distributions, inferred lateral variations in effective viscosity, power-law behavior, and the known far-field velocity boundary conditions are defined. Body forces are the differences in gravity potential energy per unit area (GPE), calculated by performing depth integration of vertical stress from the surface down to a common depth reference (20 km below sea level). In our treatment of the seismogenic layer, depth-integrated viscosities are proportional to the assumed long-term friction on faults (expected deviatoric stress at fault failure) and inversely proportional to the long-term strain rates (the known fault slip rates). The velocity boundary conditions are defined using PA-NA, CO-NA, RI-NA, and JF-NA plate motion estimates. Self-consistent dynamic strain rate tensor solutions to the force-balance equations were solved for and scored with kinematic strain rate tensor and velocity fields of western North America, obtained from a large set of highly detailed Quaternary fault observations (e.g., United States Geologic Survey Quaternary fault and fold data base of the United States). We use fault data from present-day to 750 ka to investigate models using a range of long-term fault friction coefficients from 0.02 -- 1.0 under hydrostatic pore pressure conditions. Evaluation of fitness of the dynamic solutions to deformation indicators is achieved using two different measures. In one measure, the forward dynamic strain rate tensor styles are scored by misfit to the kinematic strain rate tensor styles inferred from Kostrov summation of Quaternary fault observations. In a second measure, the dynamic model velocity fields are scored via reduced chi-square misfit with the long-term kinematic model velocity field defined by Quaternary fault observations. Models constructed with low fault friction coefficients (? < 0.20) achieve a vastly superior fit to Quaternary fault observations than do models with intermediate or high fault friction coefficients. Successful models require a weak and distributed fault fabric in which the deviatoric stresses associated with internal crustal buoyancies in the Basin and Range Province dominate over deviatoric stresses associated with velocity boundary conditions. The deformation field in western North America therefore suggests and supports the premise of a sufficiently dense fabric of faults that possess low long-term friction coefficients of 0.10--0.20.

Klein, E. C.; Holt, W. E.; Flesch, L. M.; Haines, A. J.

2008-12-01

336

Volcanism in response to plate flexure.  

PubMed

Volcanism on Earth is known to occur in three tectonic settings: divergent plate boundaries (such as mid-ocean ridges), convergent plate boundaries (such as island arcs), and hot spots. We report volcanism on the 135 million-year-old Pacific Plate not belonging to any of these categories. Small alkalic volcanoes form from small percent melts and originate in the asthenosphere, as implied by their trace element geochemistry and noble gas isotopic compositions. We propose that these small volcanoes erupt along lithospheric fractures in response to plate flexure during subduction. Minor extents of asthenospheric melting and the volcanoes' tectonic alignment and age progression in the direction opposite to that of plate motion provide evidence for the presence of a small percent melt in the asthenosphere. PMID:16873612

Hirano, Naoto; Takahashi, Eiichi; Yamamoto, Junji; Abe, Natsue; Ingle, Stephanie P; Kaneoka, Ichiro; Hirata, Takafumi; Kimura, Jun-Ichi; Ishii, Teruaki; Ogawa, Yujiro; Machida, Shiki; Suyehiro, Kiyoshi

2006-09-01

337

Mixed Convection Boundary Layer Flow over a Moving Vertical Flat Plate in an External Fluid Flow with Viscous Dissipation Effect  

PubMed Central

The steady boundary layer flow of a viscous and incompressible fluid over a moving vertical flat plate in an external moving fluid with viscous dissipation is theoretically investigated. Using appropriate similarity variables, the governing system of partial differential equations is transformed into a system of ordinary (similarity) differential equations, which is then solved numerically using a Maple software. Results for the skin friction or shear stress coefficient, local Nusselt number, velocity and temperature profiles are presented for different values of the governing parameters. It is found that the set of the similarity equations has unique solutions, dual solutions or no solutions, depending on the values of the mixed convection parameter, the velocity ratio parameter and the Eckert number. The Eckert number significantly affects the surface shear stress as well as the heat transfer rate at the surface. PMID:23577156

Bachok, Norfifah; Ishak, Anuar; Pop, Ioan

2013-01-01

338

Double Diffusive Magnetohydrodynamic (MHD) Mixed Convective Slip Flow along a Radiating Moving Vertical Flat Plate with Convective Boundary Condition  

PubMed Central

In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, , local Nusselt number, , and local Sherwood number are shown and explained through tables. PMID:25343360

Rashidi, Mohammad M.; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J.; Freidoonimehr, Navid

2014-01-01

339

Double Diffusive Magnetohydrodynamic (MHD) Mixed Convective Slip Flow along a Radiating Moving Vertical Flat Plate with Convective Boundary Condition.  

PubMed

In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, [Formula: see text], local Nusselt number, [Formula: see text], and local Sherwood number [Formula: see text] are shown and explained through tables. PMID:25343360

Rashidi, Mohammad M; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J; Freidoonimehr, Navid

2014-01-01

340

Wide-angle seismic constraints on the evolution of the deep San Andreas plate boundary by Mendocino triple junction migration  

USGS Publications Warehouse

Recent wide-angle seismic observations that constrain the existence and structure of a mafic layer in the lower crust place strong constraints on the evolution of the San Andreas plate boundary system in northern and central California. Northward migration of the Mendocino Triple Junction and the subducted Juan de Fuca lithospheric slab creates a gap under the continent in the new strike-slip system. This gap must be filled by either asthenospheric upwelling or a northward migrating slab attached to the Pacific plate. Both processes emplace a mafic layer, either magmatic underplating or oceanic crust, beneath the California Coast Ranges. A slab of oceanic lithosphere attached to the Pacific plate is inconsistent with the seismic observation that the strike-slip faults cut through the mafic layer to the mantle, detaching the layer from the Pacific plate. The layer could only be attached to the Pacific plate if large vertical offsets and other complex structures observed beneath several strike-slip faults are original oceanic structures that are not caused by the faults. Otherwise, if oceanic slabs exist beneath California, they do not migrate north to fill the growing slab gap. The extreme heat pulse created by asthenospheric upwelling is inconsistent with several constraints from the seismic data, including a shallower depth to the slab gap than is predicted by heat flow models, seismic velocity and structure that are inconsistent with melting or metamorphism of the overlying silicic crust, and a high seismic velocity in the upper mantle. Yet either the Pacific slab model or the asthenospheric upwelling model must be correct. While the mafic material in the lower crust could have been emplaced prior to triple junction migration, the deeper slab gap must still be filled. A preexisting mafic layer does not reduce the inconsistencies of the Pacific slab model. Such material could, however, compensate for the decrease in mafic magma that would be produced if asthenospheric upwelling occurred at a lower temperature. These low temperatures, however, may be inconsistent with asthenospheric rheology.

Hole, J.A.; Beaudoin, B.C.; Henstock, T.J.

1998-01-01

341

Eclogites and related metamorphism in the North America-Caribbean plate boundary: An example from the Motagua fault zone, Guatemala (Invited)  

Microsoft Academic Search

Active volcanic arcs and strike-slip fault systems characterize the present-day Caribbean Plate margins. The northern boundary of the Caribbean plate in Guatemala is the Motagua fault zone (MFZ). Along the MFZ in central and eastern Guatemala, eclogite- and jadeitite-bearing serpentinite-matrix mélange are exposed stretching ˜200 km on either side of the Motagua-Polochic fault system. The MFZ eclogites and related high-pressure

T. Tsujimori; G. A. Hernandez Pineda

2009-01-01

342

Heat exchange in boundary layer on permeable plate at injection and combustion  

NASA Astrophysics Data System (ADS)

The peculiarities of the heat and mass exchange in a laminar boundary layer with combustion at the injection of the fuel mixture H2/N2 through the permeable surface are considered. It is shown that at a certain value of the injection parameter, the value of the heat flux into the wall averaged over the length has a maximum. An analytic estimate is proposed for determining the maximum heat flux at the combustion depending on the injection intensity. The obtained relations agree with the results of experimental studies and numerical modelling.

Lukashov, V. V.; Terekhov, V. V.; Hanjali?, K.

2013-12-01

343

Hydrodynamic and hydroelastic analyses of a plate excited by the turbulent boundary layer  

NASA Astrophysics Data System (ADS)

Recent studies have demonstrated that the characterisation of wall-pressure fluctuations for surface ships is of great interest not only for military applications but also for civil marine vehicles. A ship model towed in a towing tank is used to perform pressure and structural measurements at high Reynolds numbers. This facility provides ideal flow conditions because background turbulence and noise are almost absent. Free surface effects are naturally included in the analysis, although in the particular section chosen for the present study do not have significant consequences on pressure spectra. Scaling laws for the power spectral density are identified providing the possibility to estimate pressure spectra for different flow conditions and in particular for full-scale applications. The range of validity of some theoretical models for the cross-spectral density representation is analysed by direct comparison with experimental data of wall-pressure fluctuations measured in streamwise and spanwise direction. In a second phase, an indirect validation is performed by comparing the measured vibrational response of an elastic plate inserted in the catamaran hull with that obtained numerically using, as a forcing function, the modelled pressure load. In general, marine structures are able to accept energy mainly from the sub-convective components of the pressure field because the typical bending wavenumber values are usually lower than the convective one; thus, a model that gives an accurate description of the phenomenon at low wavenumbers is needed. In this work, it is shown that the use of the Chase model for the description of the pressure field provides a satisfactory agreement between the numerical and the experimental response of the hull plate. These experimental data, although acquired at model scale, represent a significant test case also for the real ship problem.

Ciappi, E.; Magionesi, F.; de Rosa, S.; Franco, F.

2009-02-01

344

Sub-crustal earthquakes within the Australia-Pacific plate boundary zone beneath the Southern Alps, New Zealand  

NASA Astrophysics Data System (ADS)

Sub-crustal earthquakes have been observed sporadically for ?40 years in the central South Island of New Zealand. We report on 20 events recorded between December 2008 and February 2012 near the Alpine Fault in the continental collision zone between the Australian and Pacific plates. A subset of 18 events at depths of 47-74 km occurs south of Mt. Cook and together with recently reported tremor locations indicates along-strike variations in deformation behaviour along the plate boundary. The sub-crustal earthquakes south of Mt. Cook increase in depth, frequency and size southwards towards the Puysegur subduction zone. Focal mechanisms could be determined for 14 earthquakes and exhibit predominantly strike-slip and reverse faulting solutions. Stress inversion analysis of the focal mechanisms yields a stress field favouring oblique-reverse faulting. We interpret the geographic and vertical distributions of these sub-crustal events in relation to a previously proposed tectonic model of a remnant passive margin that formed south of New Zealand in the Eocene and was overridden when dextral strike-slip motion initiated on the Alpine Fault. We infer that sub-crustal earthquakes occur along the leading edge of this structure, which is attached to the continental Australian crust.

Boese, C. M.; Stern, T. A.; Townend, J.; Bourguignon, S.; Sheehan, A.; Smith, E. G. C.

2013-08-01

345

Plate Boundary Observatory Nucleus Education and Outreach: Bringing GPS and Data- Rich Activities Into College and Secondary Earth Science Classrooms  

NASA Astrophysics Data System (ADS)

Incorporating scientific data into the curriculum provides students with insight into elements of the scientific process such as developing questions and hypotheses, understanding how data are collected, evaluating data quality and limitations, and formulating conclusions based on scientific results (Manduca et al., 2003.) UNAVCO, a geodetic consortium and co-administrator of the Plate Boundary Observatory Nucleus project, seeks to increase public appreciation and understanding of Earth deformation processes and their societal relevance through education and outreach. To that end, we are developing place-based instructional materials for college and secondary Earth science classrooms in which GPS data are used to teach students about plate tectonics. To assess the needs of our users, we conducted interviews with college geoscience faculty from a variety of institution types and focus groups with secondary Earth science teachers to solicit feedback on the types of educational materials that they would likely use in their classrooms. We are engaging members of the scientific and educational communities to develop the materials and are catering the modules to accommodate diverse groups of learners and learning styles. In addition, we have completed and scheduled several professional development opportunities on the local and national levels for college and university faculty and secondary teachers and have created a new education and outreach website. Our education programs are being assessed by an external evaluator. We will present interview and focus group results, report on the status of our education programs, and discuss upcoming UNAVCO education activities.

Walker, B.; Eriksson, S. C.

2006-05-01

346

Deformation across the Pacific-North America plate boundary near San Francisco, California  

USGS Publications Warehouse

We have detected a narrow zone of compression between the Coast Ranges and the Great Valley, and we have estimated slip rates for the San Andreas, Rodgers Creek, and Green Valley faults just north of San Francisco. These results are based on an analysis of campaign and continuous Global Positioning System (GPS) data collected between 1992 and 2000 in central California. The zone of compression between the Coast Ranges and the Great Valley is 25 km wide. The observations clearly show 3.8??1.5 mm yr-1 of shortening over this narrow zone. The strike slip components are best fit by a model with 20.8??1.9 mm yr-1 slip on the San Andreas fault, 10.3??2.6 mm yr-1 on the Rodgers Creek fault, and 8.1??2.1 mm yr-1 on the Green Valley fault. The Pacific-Sierra Nevada-Great Valley motion totals 39.2??3.8 mm yr-1 across a zone that is 120 km wide (at the latitude of San Francisco). Standard deviations are one ??. The geodetic results suggest a higher than geologic rate for the Green Valley fault. The geodetic results also suggest an inconsistency between geologic estimates of the San Andreas rate and seismologic estimates of the depth of locking on the San Andreas fault. The only convergence observed is in the narrow zone along the border between the Great Valley and the Coast Ranges.

Prescott, W. H.; Savage, J. C.; Svarc, J. L.; Manaker, D.

2001-01-01

347

Low heat flow inferred from >4 Gyr zircons suggests Hadean plate boundary interactions.  

PubMed

The first approximately 600 million years of Earth history (the 'Hadean' eon) remain poorly understood, largely because there is no rock record dating from that era. Detrital Hadean igneous zircons from the Jack Hills, Western Australia, however, can potentially provide insights into the conditions extant on our planet at that time. Results of geochemical investigations using these ancient grains have been interpreted to suggest the presence of a hydrosphere and continental crust before 4 Gyr. An underexploited characteristic of the >4 Gyr zircons is their diverse assemblage of mineral inclusions. Here we present an examination of over 400 Hadean zircons from Jack Hills, which shows that some inclusion assemblages are conducive to thermobarometry. Our thermobarometric analyses of 4.02-4.19-Gyr-old inclusion-bearing zircons constrain their magmatic formation conditions to about 700 degrees C and 7 kbar. This result implies a near-surface heat flow of approximately 75 mW m(-2), about three to five times lower than estimates of Hadean global heat flow. As the only site of magmatism on modern Earth that is characterized by heat flow of about one-quarter of the global average is above subduction zones, we suggest that the magmas from which the Jack Hills Hadean zircons crystallized were formed largely in an underthrust environment, perhaps similar to modern convergent margins. PMID:19037314

Hopkins, Michelle; Harrison, T Mark; Manning, Craig E

2008-11-27

348

A 2006 earthquakes series at the Colima rift and its relationship to the Rivera-Cocos plate boundary  

NASA Astrophysics Data System (ADS)

From July 31 through 13 August 2006 a series of fourteen earthquakes (M 3.9 to 6.1) occurred in the western end of the Central Mexican Volcanic Belt (CMVB) in twenty five days period. The most prominent earthquake (Mw 6.1) occurred on 11 August 2006 at 14:30 UTC (9:30 local time) approximately at 18.37° N, 101.25° W and 81 km depth. The epicenter was less than 40 km from Huetamo, Michoacan a 41,250-inhabitant city and 60 km from the El Infiernillo dam embayment the third largest hydroelectric plant in Mexico. This earthquake was widely felt through out the region with minor to moderate reported damage. In Mexico City 250 km away from the epicenter the earthquake, produced alarm among the population and several buildings evacuated. The earthquake series developed into two activity clusters one centered in the coast and separated about 300 km from a second inland cluster. The initial coastal cluster consisted of a nearly linear activity distribution which includes two shallow-depth earthquakes and reverse faulting mechanism with a slight left lateral strike-slip component and a possible fault planes trending roughly east-west. Two normal faulting earthquakes located at the extremes of the graben system, and fault planes oriented in a nearly north-south direction followed. The earthquakes are located approximately between the trench and the coast along the El Gordo-Colima graben system, which has been proposed as the continuation of the diffuse boundary between the Rivera and Cocos plates. The reverse faulting earthquakes are congruent either, with the expected subduction of the Rivera or Cocos plate under the North America plate and the normal faulting earthquake that can be associated to motions in the graben.

Yamamoto, J.; Jimenez, Z.

2013-12-01

349

Stability of supersonic boundary layer on a porous plate with a flexible coating  

NASA Astrophysics Data System (ADS)

The development of disturbances in the boundary layer of compressible gas on a flexible surface has been investigated in the linear and nonlinear approximations (the weakly nonlinear stability theory). The regimes of moderate (the Mach number M = 2) and high (M = 5.35) supersonic velocities as well as a model of a porous wall, on which a flexible film is spanned, have been considered. The boundary conditions for disturbances with regard for their transformation by a flexible porous coating have been derived. The character of the variation of the coefficients of the stream-wise growth of linear oscillations of different nature (the vortex waves of the first mode and the acoustic waves of the second mode) is shown. The direction and the degree of their deformations are determined by the flexible coating parameters. It is found that at moderate Mach numbers, the stabilization of disturbances and the diminution of increments occur, whereas at high M on a surface with a film, the acoustic components are destabilized, which may lead to an earlier onset of nonlinear processes. The nonlinear interactions in three-wave symmetric triplets between the vortex waves at M = 2 and between the waves of different nature at M = 5.35 are considered. In the latter case, the plane acoustic wave is the pumping wave, which excites the three-dimensional subharmonic components of vortex nature.

Gaponov, S. A.; Terekhova, N. M.

2014-04-01

350

Plate Tectonics  

NSDL National Science Digital Library

This interactive Flash explores plate tectonics and provides an interactive map where users can identify plate boundaries with name and velocities as well as locations of earthquakes, volcanoes, and hotspots. The site also provides animations and supplementary information about plate movement and subduction. This resource is a helpful overview or review for introductory level high school or undergraduate physical geology or Earth science students.

Smoothstone; Company, Houghton M.

351

The Oligocene-Miocene Pacific-Australia plate boundary, south of New Zealand: Evolution from oceanic spreading to strike-slip faulting  

Microsoft Academic Search

Since the Eocene, the Pacific—Australia plate boundary south of New Zealand has evolved from a spreading system into a transform boundary. Swath data acquired in the Southeast Tasman oceanic crust, between the Macquarie Ridge complex and the Resolution Ridge system, show that the spreading fabric changes orientation southwards along the Puysegur Trench, striking successively N60°E, N85°E and N120°E. This reflects

Geoffroy Lamarche; Jean-Yves Collot; Ray A. Wood; Marc Sosson; Rupert Sutherland; Jean Delteil

1997-01-01

352

Numerical Simulation of Inlet Bleed with Circular Holes on Plate Under Shock-Wave/Boundary-Layer Interactions  

NASA Technical Reports Server (NTRS)

A numerical study was performed to investigate the shock-wave/boundary-layer interactions on a flat plate with bleed through one or more circular holes that vent into a plenum. The bleed-hole patterns considered for the study include in-line multiple holes and staggered multiple-row holes that are configured to simulate the patterns used in inlet bleed systems of high performance aircraft. The focus of the study was to examine how the bleed through multiple holes affect bleed rate and the pressure and Mach number distributions. Since the bleed performance was found sensitive to the change in bleed conditions, a computational procedure was developed to give a good turnaround computational time for parametric studies involving changes in bleed hole geometry and the structure of shock-wave/boundary-layer flowfield. The procedure includes the grid-generation methodology and the flow simulation with solutions from the Navier-Stokes equations. The computational techniques permit analysis of complex bleed systems and make possible the investigation of a broader range of design variables associated with inlet bleed operation.

Chyu, Wei J.; Rimlinger, Mark J.; Shih, Tom I.-P.

1994-01-01

353

Influence of boundary stress singularities on the vibration of clamped and simply-supported sectorial plates with arbitrary radial edge conditions  

NASA Astrophysics Data System (ADS)

This paper extends previous studies made for sectorial plates having re-entrant (i.e., interior) corners causing stress singularities, to provide accurate frequencies when the circular edge is either clamped or simply-supported. An extensive review of the literature is also given herein spanning nearly the past two decades explaining the free vibration characteristics of sectorial plates. In this work, the classical Ritz method is employed with two sets of admissible functions assumed for the transverse vibratory displacements. These sets include: (1) mathematically complete algebraic-trigonometric polynomials which guarantee convergence to exact frequencies as sufficient terms are retained and (2) corner functions which account for the bending moment singularities at the re-entrant vertex corner of the radial edges having arbitrary edge conditions. Extensive convergence studies summarized herein confirm that the corner functions substantially enhance the convergence and accuracy of non-dimensional frequencies for sectorial plates having either a clamped or hinged circumferential edge and various combinations of clamped, hinged, and free conditions on the radial edges. Accurate (to at least four significant figure) frequencies and normalized contours of the transverse vibratory displacement are presented for the spectra of sector angles [90°, 180° (semi-circular), 270°, 300°, 330°, 350°, 355°, 360° (complete circular)] causing a re-entrant vertex corner of the radial edges. For sector angles of 360°, a clamped-clamped, clamped-hinged, clamped-free, hinged-free or free-free radial crack ensues. One general observation is the substantial reduction in the first six frequencies as the sector angle increases for all plates, except in the first two modes of plates having free-free radial edges.

McGee, O. G.; Kim, J. W.; Kim, Y. S.

2010-12-01

354

Resistance of plate motion due to continental deformation (Invited)  

NASA Astrophysics Data System (ADS)

Convergent plate margins that produce high mountains often induce deformation that extends for hundreds to thousands kilometers inboard of the plate boundary. Buoyancy forces that are derived from this thickened, elevated continental crust are commonly thought to resist further convergence and contribute to changes in plate rates as the balance of forces on a plate boundary evolves. For orogens that develop broad plateau-style topography, the strength of the deforming continent and the distance over which it deforms may also contribute to plate forces, although this forcing has rarely been considered. For example, the post-collisional slowing of India with respect to Eurasia challenges the role of topography as the cause of decreasing convergence rates and instead favors the role of deforming a confined mantle lithosphere as the cause of slowing. Here, geologic evidence suggests that compressional deformation began at the distal extent of the orogen when continental collision initiated and that the majority of deformation since has remained localized along what can be considered to be a stationary boundary. As post-collisional convergence continued, convergence rates have declined exponentially as did the distance across the intervening region of deformation. The decline in rate and distance occurred in tandem such that the bulk average strain rate across the orogen remained constant and is equal to the modern strain rate determined by GPS. For both linear and non-linear constitutive relationships, a constant average strain rate implies constant average stress (or constant forcing). A constant force per unit length of the plate boundary might be explained by the viscous resistance of the deforming continental mantle lithosphere, as opposed to a change in forces that would be expected from the buoyancy of the evolving high topography. A viscous resistance of the continental lithosphere has not previously been considered as a type of plate forcing, and the Indo-Asia orogen may offer one extreme example of such. Other examples include the ongoing Arabian-Eurasia continental collision and the ocean-continent subduction beneath South America, where exponentially decreasing convergence rates and mountain building are also observed. Long-lived, far-field deformation in the Arabian example may provide analogous to the Tibet case where decreasing convergence rates follow a decrease over which that convergence is absorbed by continental deformation. Unlike Tibet and Arabia, the outward expansion of deformation away from the plate boundary in the Andean orogen suggests that bulk strain rates must have decreased through time. Possibly, such differences may be related to time-dependent rheologic changes associated with subduction-related magmatism, changes in the frictional resistance along the plate contact, or the diminished role of viscous resistance in subduction settings compared to their continental collision counterpart.

Clark, M. K.

2013-12-01

355

Direct numerical simulation methods of hypersonic flat-plate boundary layer in thermally perfect gas  

NASA Astrophysics Data System (ADS)

High-temperature effects alter the physical and transport properties of air such as vibrational excitation in a thermally perfect gas, and this factor should be considered in order to compute the flow field correctly. Herein, for the thermally perfect gas, a simple method of direct numerical simulation on flat-plat boundary layer is put forward, using the equivalent specific heat ratio instead of constant specific heat ratio in the N-S equations and flux splitting form of a calorically perfect gas. The results calculated by the new method are consistent with that by solving the N-S equations of a thermally perfect gas directly. The mean flow has the similarity, and consistent to the corresponding Blasius solution, which confirms that satisfactory results can be obtained basing on the Blasius solution as the mean flow directly in stability analysis. The amplitude growth curve of small disturbance is introduced at the inlet by using direct numerical simulation, which is consistent with that obtained by linear stability theory. It verified that the equation established and the simulation method is correct.

Jia, WenLi; Cao, Wei

2014-01-01

356

Cratonic platform and foredeep response to plate margin convergence: Devonian through Mississippian subsidence history in western Montana and east-central Idaho  

SciTech Connect

Devonian and Mississippian sedimentary rocks of western Montana and east-central Idaho were deposited on a cratonic platform that faced a northern extension of the Antler foredeep. Subsidence analyses of this sequence and isopach maps illustrate regional patterns of subsidence related to convergence along the western North American plate margin. Tectonic stresses affected deposition on platform areas which were hundreds of kilometers inboard from the ancient continental margin. Wavelengths of paleostructural elements, tectonic inversion of these structures (i.e., transition of a paleohigh into a depocenter), and time scales involved in the inversion process cannot be attributed solely to flexure or to vertical displacements by in-plane stresses but suggest reactivation of Precambrian structural trends. Late Devonian (Frasnian) platform sedimentation began during a brief interval of increased subsidence across western Montana. This interval of increased platform subsidence is greater than a Late Devonian eustatic sea level rise (determined from subsidence analyses of Devonian strata from stable cratonic areas) and suggests some tectonic event must have influenced subsidence in Montana. Thin uppermost Devonian Strata contain numerous unconformities that may be related to flexure of the platform plus eustatic sea level fluctuations. Rapid subsidence across Montana during the Early Mississippian (Kinderhookian) resulted in a condensed platform sequence, which is overlain by deep water shaly carbonates. Rapid subsidence continued into the Osagean then slowed, allowing progradation of carbonate platform facies across Montana. A regional karst surface on top of the Meramecian platform coincides with conglomerate deposition and increased subsidence rates in the foredeep; unconformity durations on the platform also increase to the east.

Dorobek, S.L.; Reid, S.K. (Texas A and M Univ., College STation, TX (USA)); Elrich, M. (Virginia Polytechnic Institute and State Univ., Blacksburg (USA)); Bond, G.C. (Lamont-Doherty Geological Observatory, Palisades, NY (USA)); Kominz, M.A. (Univ. of Texas, Austin (USA))

1990-05-01

357

Trench-parallel shortening in the forearc caused by subduction along a seaward-concave plate boundary: Insights from analogue modelling experiments  

NASA Astrophysics Data System (ADS)

Three-dimensional thermo-mechanical analogue experiments are employed to test the hypothesis that oceanic subduction along a seaward-concave plate boundary can generate trench-parallel shortening in the forearc near the axis of curvature. The model deformation is analyzed with a Particle Imaging Velocimetry (PIV) system that allows for comparison of forearc deformation along the oblique limbs of the curved plate boundary and near the axis of curvature. Moreover, PIV allows for separation of the trench-parallel and trench-perpendicular components of strain, regardless of trench orientation. The resulting deformation maps show a remarkable symmetry and indicate drag of the forearc above the interplate coupling area towards the axis of curvature. Trench-perpendicular profiles show that along the oblique limbs of the plate boundary, the forearc is submitted to trench-normal shortening and trench-parallel shearing but not trench-parallel shortening or extension. This contrasts with the situation near the axis of symmetry where the forearc is submitted to trench-parallel and trench-perpendicular normal shortening, but is not sheared. The experimental results confirm that trench-normal thrusts observed in the fore-arc of the Central-Andes can be a mechanical consequence of subduction along a seaward-concave plate boundary if the degree of interplate coupling is large.

Boutelier, D.; Oncken, O.; Cruden, A. R.

2014-01-01

358

Investigation of the interaction of an unsteady shock wave and the boundary layer on a flat plate in the transition regime  

Microsoft Academic Search

The interaction between a shock wave and the boundary layer on a plate has been considered in a number of experimental studies. These have mainly been concerned with the investigation of the conditions of onset of separation, the structure and properties of the flow near the interaction zone and, moreover, the pressure and heat flux distributions in that zone [1--6].

S. V. Kuimov; V. S. Khlebnikov

1992-01-01

359

Numerical approaches to the evaluation of foreland basin in an active convergence boundary for CO2 sequestration  

NASA Astrophysics Data System (ADS)

Greenhouse gas control has become one of the most critical environmental issues since last two decades. Since then, underground geological storage has been recognized as an important technique for CO2 mitigation. The geological reservoirs can trap CO2 by a number of mechanisms, including stratigraphic and structural trapping, hydrodynamic trapping and geochemical trapping. However, the detailed evaluation on capacity of reservoir formation, sealing caprock and stability of geological environment should be carefully made when consider a potential site as CO2 reservoir. IPCC suggested that potential sites located in active plate margin must be carefully evaluated on an individual basis. However, Cenozoic foreland basin is one of the most dominant tectonic units in the west Pacific margin, including the study area (Taiwan), and is naturally characterized by many preferred features for geological CO2 storage. Accordingly, in this study, foreland basin will be assessed in both aspects of a conceptual framework and an individual local case with a full-scale numerical model. The foreland basin along Taiwan Orogeny can be subdivided into two basins (Taihsi Basin and Tainan Basin) by Peikang High region. Taihsi Basin is a preferred potential storage due to considerable thickness of sandstone in the range of injection depth. Accordingly, a detailed geological profile across the Taihsi Basin has been established with magnetotelluric and seismic reflection surveys in a preliminary study, which were used for evaluating the Taihsi Basin and estimating the amount of CO2 sequestration under various geological scenarios in this study. The results demonstrate that the north part of Taihsi Basin were less faulted and folded and is the most favor potential site. The injected CO2 naturally migrates toward the Taiwan Strait due to the gentle dipping; and, CO2 will finally reach the forebulge of the basin in about twenty thousand years. In addition, the reservoir formation is truncated by a thick clay formation in front of the forebulge. The CO2 can be eventually trapped in the wedge sealed by the clay formation.

He, Sinda

2013-04-01

360

Supraslab earthquake clusters above the subduction plate boundary offshore Sanriku, northeastern Japan: Seismogenesis in a graveyard of detached seamounts?  

NASA Astrophysics Data System (ADS)

Thousands of offshore repeating earthquakes with low-angle thrust focal mechanisms occur along the subduction plate boundary of NE Japan. Double-difference relocation methods using P- and S-wave arrivals reveal clusters of events above these repeating events. To assure good depth control we restrict our study to events that are close to seismic stations. These "supraslab" earthquake clusters are regional features at depths of 25 to 50 km, and most of these clusters are below the depth of the forearc Moho, which we determined from converted waves. Seismicity over this depth range does not occur under the inland area of NE Japan except just below the vicinity of the arc volcanoes. Re-entrants in the inner trench slope indicate that repeated collisions of seamounts have occurred in the past. Our preliminary interpretation of supraslab clusters is that they represent seismicity in seamounts detached from the Pacific plate during slab descent, driven by the resistance of seamounts to subduction. Detachment during slab descent probably occurs on the sedimented and hydrothermally altered seafloor on which seamounts were originally constructed since these are known as zones of weakness during active island growth. High fluid pressure produced during dehydration of clay minerals and other low-temperature hydrous minerals could enable detachment at depths. Seamount crust is thus accreted to forearcs, possibly leading to a long-term component of near-coastal uplift. Supraslab earthquake clusters may be our most direct evidence of the fates of seamounts and suggest that tectonic underplating is actively occurring in this subduction system.

Uchida, Naoki; Kirby, Stephen H.; Okada, Tomomi; Hino, Ryota; Hasegawa, Akira

2010-09-01

361

Measuring present-day strain rates along the Fish Lake Valley fault system, Pacific-North America plate boundary  

NASA Astrophysics Data System (ADS)

A fundamental issue in modern tectonics is the degree to which spatial and temporal variations exist in strain accumulation and release along evolving plate boundaries. The eastern California shear zone (ECSZ) is located east of the San Andreas fault and contains a complex network of structures that accommodate ~25% of the relative displacement between the Pacific and North American plates. Geodetic data indicate strain accumulation at a rate of 12±2 mm/yr along four main structures in the ECSZ. The Death Valley-Fish Lake Valley fault, the prominent and longest fault in the ECSZ at ~300km, is observed to be the fastest slipping fault in the region storing elastic strain at a rate of 3-8 mm/yr. Recently determined long-term slip rates (103 - 106 year timescale) indicate a pattern of decreasing velocity moving north through Fish Lake Valley (FLV) from ~6 mm/yr to zero, presumably because strain is transferred onto extensional faults located to the east. This study intends to determine the short-term (decadal timescale) GPS-derived displacement fields along the FLV fault to test whether spatial patterns of geodetic and geologic rates are consistent through time. In a series of two GPS campaigns in 2010 and 2011, eleven geodetic monuments, spaced 15-20 km apart, were surveyed in and around FLV. In addition, campaign data from previous surveys has been acquired from UNAVCO. The combined data sets are used to calculate the relative motion along the fault. Modern strain rates will be presented in comparison to published long-term rates.

Johnson, C. W.; Frankel, K. L.; Newman, A. V.; Lifton, Z. M.

2011-12-01

362

Pore pressure near the plate boundary decollement in the Nankai Trough, southwest Japan  

NASA Astrophysics Data System (ADS)

We predict pore pressure distribution within the Nankai Trough accretionary prism via a theoretical based approach. The decollement (a detachment that separates a deformed accretionary prism from the underthrust sediments) in the Nankai Trough off the Muroto peninsula is developed within a hemipelagic mudstone sequence and it is well defined by a prominent reverse-polarity reflector on seismic profiles. From this polarity reversal, the decollement is inferred to be a low acoustic impedance zone. The low acoustic impedance at the decollement can be explained by high porosity sustained by pore fluid pressure. Because the pore pressure along the decollement influences the frictional characteristics, it plays a key role in the earthquake mechanism and deformation features of the accretionary prism. Many studies of pore pressure prediction from seismic reflection data rely on empirical relations. Here, we present a method for determining pore pressure based on rock physics theory from seismic interval velocities and well data. In our method, we introduce the aspect ratio distribution of pore space. From the aspect ratio distribution calibrated by well data, we calculate theoretical velocity parameterized by effective pressure via Differential Effective Medium (DEM) theory and compare it with seismic P-wave velocity derived from 3-D reflection tomography. By iteratively fitting the theoretical velocity to the seismic interval velocity, we estimate in situ effective pressure. The results demonstrate the abnormal high pore pressure within the subducting sedimentary sequence. Two-third of the effective pressure at hydrostatic conditions is supported by overpressure in the underthrust sequence. This high pore fluid pressure can account for the weak coupling along the decollement and shallowly tapered geometry of the accretionary prism. The overpressure within the accreted section also increases from the deformation front. Seismic profiles image the tectonic thickening of the accretionary prism that has occurred following displacement along the frontal-thrust. This increase of vertical load by the thickened prism and low permeable marine sediment may raise the pore fluid pressure within the accretionary prism. Furthermore, low permeable cap along the decollement may seal the pore pressure of the underthrust sequence, and cause pressure boundary at the decollement.

Tsuji, T.; Tokuyama, H.; Pisani, P. C.; Moore, G.

2006-12-01

363

Observing active deformation of volcanoes in North America: Geodetic data from the Plate Boundary Observatory and associated networks  

NASA Astrophysics Data System (ADS)

The EarthScope Plate Boundary Observatory (PBO), operated by UNAVCO, records deformation of the geologically diverse North America western plate boundary, with subnetworks of instruments concentrated at selected active and potentially active volcanoes. These sensors record deformation and earthquakes and allow monitoring agencies and researchers to analyze changes in ground motion and seismicity. The intraplate volcanoes at Yellowstone and Long Valley are characterized by uplift/subsidence cycles, high seismicity, and hydrothermal activity but there have been no historic eruptions at either volcano. PBO maintains dense GPS networks of 20-25 stations at each of these volcanoes, with an additional 5 boreholes at Yellowstone containing tensor strainmeters, short-period seismometers, and borehole tiltmeters. Subduction zone volcanoes in the Aleutian Arc have had multiple historic eruptions, and PBO maintains equipment at Augustine (8 GPS), Akutan (8 GPS, 4 tiltmeters), and Unimak Island (14 GPS, 8 tiltmeters). The Unimak stations are at the active Westdahl and Shishaldin edifices and the nearby, inactive Isanotski volcano. In the Cascade Arc, PBO maintains networks at Mount St. Helens (15 GPS, 4 borehole strainmeters and seismometers, 8 borehole tiltmeters), Shasta (7 GPS, 1 borehole strainmeter and seismometer), and Lassen Peak (8 GPS). Data from many of these stations in the Pacific Northwest and California are also provided as realtime streams of raw and processed data. Real-time GPS data, along with high-rate GPS data, will be an important new resource for detecting and studying future rapid volcanic deformation events and earthquakes. UNAVCO works closely with the USGS Volcano Hazards Program, archiving data from USGS GPS stations in Alaska, Cascadia, and Long Valley. The PBO and USGS networks combined provide more comprehensive coverage than PBO alone, particularly of the Cascade Arc, where the USGS maintains a multiple instruments near each volcano. Ground-based instruments are supplemented by remote sensing data sets. UNAVCO supports the acquisition of InSAR and LiDAR imaging data, with archiving and distribution of these data provided by UNAVCO and partner institutions. We provide descriptions and access information for geodetic data from the PBO volcano subnetworks and their applications to monitoring for scientific and public safety objectives. We also present notable examples of activity recorded by these instruments, including the 2004-2010 accelerated uplift episode at the Yellowstone caldera and the 2006 Augustine eruption.

Puskas, C. M.; Phillips, D. A.; Mattioli, G. S.; Meertens, C. M.; Hodgkinson, K. M.; Crosby, C. J.; Enders, M.; Feaux, K.; Mencin, D.; Baker, S.; Lisowski, M.; Smith, R. B.

2013-12-01

364

Linear stability of a gas boundary layer flowing past a thin liquid film over a flat plate  

NASA Astrophysics Data System (ADS)

The flow of a gas stream past a flat plate under the influence of rainfall is investigated. As raindrops sediment on the flat plate, they coalesce to form a water film that flows under the action of shear from the surrounding gas stream. In the limit of (a) large Reynolds number, Re, in the gas phase, (b) small rainfall rate, r[dot above], compared to the free-stream velocity, U[infty infinity], and (c) small film thickness compared to the thickness of the boundary layer that surrounds it, a similarity solution is obtained that predicts growth of the liquid film like x3/4; x denotes dimensionless distance from the leading edge. The flow in the gas stream closely resembles the Blasius solution, whereas viscous dissipation dominates inside the film. Local linear stability analysis is performed, assuming nearly parallel base flow in the two streams, and operating in the triple-deck regime. Two distinct families of eigenvalues are identified, one corresponding to the well-known Tollmien Schlichting (TS) waves that originate in the gas stream, and the other corresponding to an interfacial instability. It is shown that, for the air water system, the TS waves are convectively unstable whereas the interfacial waves exhibit a pocket of absolute instability, at the streamwise location of the applied disturbance. Moreover, it is found that as the inverse Weber number (We[minus sign]1) increases, indicating the increasing effect of surface tension compared to inertia, the pocket of absolute instability is translated towards larger distances from the leading edge and the growth rate of unstable waves decreases, until a critical value is reached, We[minus sign]1 [approximate] We[minus sign]1c, beyond which the family of interfacial waves becomes convectively unstable. Increasing the inverse Froude number (Fr[minus sign]1), indicating the increasing effect of gravity compared to inertia, results in the pocket of absolute instability shrinking until a critical value is reached, Fr[minus sign]1 [approximate] Fr[minus sign]1c, beyond which the family of interfacial waves becomes convectively unstable. As We[minus sign]1 and Fr[minus sign]1 are further increased, interfacial waves are eventually stabilized, as expected. In this context, increasing the rainfall rate or the free-stream velocity results in extending the region of absolute instability over most of the airfoil surface. Owing to this behaviour it is conjectured that a global mode that interacts with the boundary layer may arise at the interface and, eventually, lead to three-dimensional waves (rivulets), or, under extreme conditions, even premature separation.

Pelekasis, Nikolaos A.; Tsamopoulos, John A.

2001-06-01

365

Jet-boundary and Plan-form Corrections for Partial-Span Models with Reflection-Plane, End-Plate, or No End-Plate in a Closed Circular Wind Tunnel  

NASA Technical Reports Server (NTRS)

A method is presented for determining the jet-boundary and plan-form corrections necessary for application to test data for a partial-span model with a reflection plane, an end plate, or no end plate in a closed circular wind tunnel. Examples are worked out for a partial-span model with each of the three end conditions in the Langley 19-foot pressure tunnel and the corrections are applied to measured values of lift, drag, pitching-moment, rolling-moment, and yawing-moment coefficients.

Sivells, James C; Deters, Owen J

1946-01-01

366

Regional provenance study of Eocene clastic sedimentary rocks within the South America-Caribbean plate boundary zone using detrital zircon geochronology  

NASA Astrophysics Data System (ADS)

Previous on- and offshore studies have postulated that the Caribbean plate has translated hundreds of kilometers eastward during the Cenozoic along strike-slip and oblique thrust faults bounding the northern margin of the continental South America plate. Two previously proposed tectonic-sedimentary models to explain the complex linkages between plate motions and sedimentation within the broad plate boundary zone include: 1) eastward bulldozing by the Caribbean plate of a single, large point source, thick Eocene proto-Maracaibo deltaic system of northwestern South America, over 1000 km to the east and incorporation of these continentally derived sediments into the ˜ 12-km-thick Barbados accretionary prism along the leading edge of the Caribbean plate; and 2) eastward bulldozing by less than 300 km of smaller point and line sources of Eocene and younger clastic sediments derived from erosion of the Guyana shield located in north-central and northeastern South America. We test both models by sampling eight Eocene localities that span a 1200-km-length of the plate boundary zone from the proto-Maracaibo delta in western Venezuela to Barbados Island in the subaerial part of the large accretionary prism bounding the eastern margin of the Caribbean plate. Ages of 972 single grains from samples at these eight localities support the multiple-source model, in which the Barbados prism was partly constructed from the bulldozing and incorporation of smaller point and line sources derived from older-than 1500 Ma crustal provinces of the Precambrian Guyana shield in central and northeastern South America. Eocene clastic sediments of the proto-Maracaibo delta derived from Paleozoic and Precambrian crustal provinces in northwestern South America are distinct in their ranges of detrital zircon ages from the ranges of the Guyana shield sources to the east.

Xie, Xiangyang; Mann, Paul; Escalona, Alejandro

2010-03-01

367

The effect of elastic boundary conditions on the dynamic response of rectangular plates. M.S. Thesis  

NASA Technical Reports Server (NTRS)

Natural frequencies and forced steady-state harmonic response for the vibration of uniform rectangular plates with edges elastically restrained against rotation and transverse translation are addressed. A single mode Rayleigh-Ritz solution is derived using functions that describe the normal modes of vibration of a beam whose ends are elastically restrained. The finite element solution is obtained for comparison. MACSYMA symbolic manipulation system is implemented as an aid to the mathematical rigor of the Ritz approach, and NASTRAN finite element code is used to model the mechanical system. Comparisons are made to published results and the solutions of this study are found to give lower frequencies for some values of boundary restraint. Steady-state harmonic amplitudes of displacement and acceleration are found to agree favorably for the two solutions. Low predictions of steady-state strain from NASTRAN result in some cases when compared to the Ritz values. Finally, a subjective assessment is made about the merit of using MACSYMA and NASTRAN.

Brewer, Terry K.

1988-01-01

368

The Plate Boundary Observatory Permanent Global Positioning System Network on Augustine Volcano Before and After the 2006 Eruption  

USGS Publications Warehouse

In September of 2004, UNAVCO and the National Science Foundation (NSF) funded EarthScope Plate Boundary Observatory (PBO) installed five permanent Continuous Global Positioning System (CGPS) stations on Augustine Volcano, supplementing one existing CGPS station operated by the Alaska Volcano Observatory. All six CGPS stations proved crucial to scientists for detecting and monitoring the precursory deformation of the volcano beginning in early May 2005, as well as for monitoring the many subsequent small inflationary and deflationary episodes that characterized the 2006 eruption. Following the eruption, in September of 2006, PBO added six additional permanent CGPS stations. The 2006 eruption and its precursors were the first significant activity of the volcano in 20 years and the PBO CGPS network provided an unprecedented opportunity to monitor and detect volcanic ground deformation on an erupting Alaskan stratovolcano. Data from the new CGPS stations coupled with the existing seismic stations provided scientists with the first real opportunity to use geodetic data and real time seismic data to assess the volcanic hazards before, during, and after an Alaskan eruption.

Pauk, Benjamin A.; Jackson, Michael; Feaux, Karl; Mencin, David; Bohnenstiehl, Kyle

2010-01-01

369

New c. 270 kyr strike-slip and uplift rates for the southern Alpine Fault and implications for the New Zealand plate boundary  

NASA Astrophysics Data System (ADS)

Along 100 km of the Alpine Fault, major valleys and glacial deposits can be matched across an 8000 m dextral offset. We use paleontologic and stratigraphic age constraints to date c. 270 ka marine sediments uplifted to 600 m elevation and overlying c. 270 ka glacial deposits related to the 8000 m dextral offset. These constraints yield a fault-proximal Australian plate uplift rate of 2.6 (-0.5/+0.4) mm/yr and an Alpine Fault dextral slip rate of 29.6 (-2.5/+4.5) mm/yr. Our rates resolve an apparent along-strike drop in strike-slip rate and instead support a relatively constant along-strike dextral slip rate of ˜28 mm/yr (˜80% of current Australian-Pacific plate boundary motion). We argue that the rate of dextral slip on the southern Alpine Fault has been relatively constant over the last ?3.5 myr, and that ductile fault processes may rate-limit the fault from accommodating a progressively higher percentage of plate boundary motion through time (i.e., the fault reached maturity long ago). The spatiotemporally constant strike-slip rate of the southern Alpine Fault and a previously published paleoseismic record of near-regular earthquake recurrence both characterize the Alpine Fault as a mature plate boundary fault zone that behaves in a constant way with behavior predictable over timescales of thousands and hundreds of thousands of years.

Barth, N. C.; Kulhanek, D. K.; Beu, A. G.; Murray-Wallace, C. V.; Hayward, B. W.; Mildenhall, D. C.; Lee, D. E.

2014-07-01

370

New insights into North America-Pacific plate boundary deformation from Lake Tahoe, Salton Sea and Southern Baja California  

E-print Network

to the Pacifi c Plate: Tectonics, v. 8, p. 99-115. Stock,c North America plate tectonics of the Neogene southwesternplate motion partitioning and the transition to seafl oor spreading in the Gulf of California: Tectonics,

Brothers, Daniel Stephen

2009-01-01

371

IODP Expedition 338: NanTroSEIZE Stage 3: NanTroSEIZE plate boundary deep riser 2  

NASA Astrophysics Data System (ADS)

The Nankai Trough Seismogenic Zone Experiment (NanTroSEIZE) is designed to investigate fault mechanics and seismogenesis along a subduction megathrust, with objectives that include characterizing fault slip, strain accumulation, fault and wall rock composition, fault architecture, and state variables throughout an active plate boundary system. Integrated Ocean Drilling Program (IODP) Expedition 338 was planned to extend and case riser Hole C0002F from 856 to 3600 meters below the seafloor (m b.s.f.). Riser operations extended the hole to 2005.5 m b.s.f., collecting logging-while-drilling (LWD) and measurement-while-drilling, mud gas, and cuttings data. Results reveal two lithologic units within the inner wedge of the accretionary prism that are separated by a prominent fault zone at ~ 1640 m b.s.f. Due to damage to the riser during unfavorable winds and strong currents, riser operations were suspended, and Hole C0002F left for re-entry during future riser drilling operations. Contingency riserless operations included coring at the forearc basin site (C0002) and at two slope basin sites (C0021 and C0022), and LWD at one input site (C0012) and at three slope basin sites (C0018, C0021 and C0022). Cores and logs from these sites comprehensively characterize the alteration stage of the oceanic basement input to the subduction zone, the early stage of Kumano Basin evolution, gas hydrates in the forearc basin, and recent activity of the shallow megasplay fault zone system and associated submarine landslides.

Moore, G. F.; Kanagawa, K.; Strasser, M.; Dugan, B.; Maeda, L.; Toczko, S.

2014-01-01

372

Nonlinear radiation heat transfer effects in the natural convective boundary layer flow of nanofluid past a vertical plate: a numerical study.  

PubMed

The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge-Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. PMID:25251242

Mustafa, Meraj; Mushtaq, Ammar; Hayat, Tasawar; Ahmad, Bashir

2014-01-01

373

Nonlinear Radiation Heat Transfer Effects in the Natural Convective Boundary Layer Flow of Nanofluid Past a Vertical Plate: A Numerical Study  

PubMed Central

The problem of natural convective boundary layer flow of nanofluid past a vertical plate is discussed in the presence of nonlinear radiative heat flux. The effects of magnetic field, Joule heating and viscous dissipation are also taken into consideration. The governing partial differential equations are transformed into a system of coupled nonlinear ordinary differential equations via similarity transformations and then solved numerically using the Runge–Kutta fourth-fifth order method with shooting technique. The results reveal an existence of point of inflection for the temperature distribution for sufficiently large wall to ambient temperature ratio. Temperature and thermal boundary layer thickness increase as Brownian motion and thermophoretic effects intensify. Moreover temperature increases and heat transfer from the plate decreases with an increase in the radiation parameter. PMID:25251242

Mustafa, Meraj; Mushtaq, Ammar; Hayat, Tasawar; Ahmad, Bashir

2014-01-01

374

Current Status of Nankai Earthquake Forecasting System based on Sequential Data Assimilation of the Slip on the Plate Boundary  

NASA Astrophysics Data System (ADS)

Interplate earthquake cycles are expressed by spatiotemporal variation of slip and slip deficit on plate interfaces. Hence, we can approximate changes in fault stress during earthquake cycles through the kinematic dislocation model in the simplified medium. By combining fault stress based on the elastic dislocation with a friction law, we can derive mathematical formulations obeying the evolution of fault slips. Actually, it has been shown that many phenomena in plate boundaries can be explained by results of numerical integration of mathematical models. Moreover, the distribution of slips on the plate interface can be presumed from the crustal deformation obtained by some instruments (e.g. GNSS or submarine pressure gage etc.). Thus, owing to developments of models for fault slips and observation networks, it is possible to predict the evolution of fault slips through the combination of model and observation. However, there are many difficulties to realize the prediction of the evolution of fault slips; Mathematical models of earthquakes are nonlinear ones with many DOFs, even though they are highly simplified. Besides, observation always contains an error, and observation sites are limited to the earth's surface. Moreover, the precise observation data are only available for recent several decades which is much shorter than a great interplate earthquake cycle. In such situation, the observation is not enough to obtain a deterministic prediction. Hence, we must prepare many simulation results (scenarios) with possible conditions. Then, for crustal deformations associated with whole scenarios, the fitness to observation is checked. Based on the fitness, likelihoods of scenarios are calculated, and each scenario is weighted by the likelihood value. Thus, the extrapolation of the ensemble of weighted scenarios should be regarded as the prediction of fault slips. To predict anticipated Nankai earthquakes in southwestern Japan, we have so far advanced the construction of the forecasting system in Nankai region based on the above concept. For investigating Nankai earthquake scenarios comprehensively, the simultaneous simulation of many conditions is performed using K computer. Moreover, for the implementation of ensemble prediction, we adopt Sequential Importance Sampling which is a kind of the data assimilation technique. Now, observation data (vertical component of GEONET) is taken from a database weekly, and using 22 sites in the Pacific coast of southwestern Japan, the likelihood of each scenario is evaluated. Results indicate that for scenarios with high likelihood, predicted horizontal deformation at GEONET sites and vertical deformation at the DONET sites are well consistent with the observation, though horizontal components of GEONET data and DONET data are not included in current data assimilation. This means the scenarios evaluated here are valid for the recent deformation data. Hence, as a next step for improving the forecasting system, we are planning to incorporate other data which characterize earthquake cycles (e.g. recurrence times, occurrence timing of past earthquakes etc.) to sequential assimilation.

Hyodo, M.; Nakata, R.; Ariyoshi, K.; Hori, T.; Kaneda, Y.

2013-12-01

375

Enigma of earthquakes at ridge-transform-fault plate-boundaries distribution of non-double couple parameter of Harvard CMT solutions  

Microsoft Academic Search

The distribution of the non-double couple parameter of shallow earthquakes reported in the Harvard CMT catalogue shows systematic characteristics depending on the epicentral locations and types of fault mechanisms. We suggest that they can be explained by the presence of subevents with different double couple mechanism in a single rupture sequence. The earthquakes at the ridge-transform-fault plate boundaries show a

Hitoshi Kawakatsu

1991-01-01