Contract Zone Research Articles

Reactivation of ancient rift systems triggers devastating intraplate earthquakes

Large historical and recent intraplate earthquakes have been concentrated along a contractional zone at the eastern margin of the Japan Sea back‐arc basin. Here we present high‐resolution three‐dimensional tomographic imaging of seismic velocities in this zone using data from a dense seismograph deployment. We discover that stepwise and tilted block structures of the basement, which are geophysical evidence of a Miocene rift system, are widely distributed beneath the thick sedimentary basin. Most aftershocks following recent intraplate earthquakes align roughly along the tilted block boundaries and are controlled by weaknesses associated with buried rift systems. Furthermore, slow anomalies are localized beneath the seismogenic zones, suggesting that fluids may have locally weakened the strength of the lower crust. We propose that stress loading through ductile creeping of the weak lower crust reactivates pre‐existing weak faults within ancient rift systems, leading to devastating intraplate earthquakes.

Why Do Player Trades Dominate Sales?

Although barter is considered to be inefficient, trades are more common than player sales in professional sports. Theory indicates that when owners have identical constant risk averse preferences, the contract zone for sales shrinks relative to that for trades. Moreover, the gap between the two contract zones becomes larger as the expected quality of the player increases. Probit estimations reveal that the likelihood a player is sold rather than traded increases with age and as the percentage of remaining career productivity decreases. An inverse relationship between player quality and the likelihood of sale for is found for hitters, but not for pitchers.

Introduction to the special section on the 2007 Chuetsu-Oki, Niigata, Japan, Earthquake

An MJMA 6.8 earthquake occurred in the offshore region of mid-Niigata prefecture, central Japan, on July 16, 2007. This earthquake killed 15 people, injured 2,016 others, and destroyed 1,300 dwellings in coastal regions along the Sea of Japan, especially in the city of Kashiwazaki. The Kashiwazaki-Kariya nuclear power plant, which is the largest nuclear generating station in the world, is located in the epicentral area and automatically powered down safely in response to the earthquake. The extended shutdown needed for its post-earthquake inspection and subsequent upgrades, however, had a significant impact on the Japanese economy. This earthquake also focused attention on some of the problems involved in providing a high level of anti-earthquake resistance to nuclear power plants in the Japanese islands. This earthquake occurred in a fold-and-thrust belt along the coast of the Sea of Japan in northern Honshu, which has been marked as a failed rift formed in the Miocene associated with the opening of the Sea of Japan (e.g., Sato, 1994). The more than 6-km-thick Neogene basin fill shows active folding and thrusting, forming a zone of late Quaternary contraction. The coast of the Sea of Japan in Niigata prefecture is also located in the zone showing a high strain rate, as observed by the continuous GPS network (Sagiya, 2004), and has been hit by many destructive earthquakes in the past, such as the 1964 Niigata earthquake (MJMA 7.4) and the 2004 mid-Niigata Prefecture earthquake (MJMA 6.8; Hirata, 2005). Studies of the 2007 Chuetsu-Oki Earthquake, as well as the 2004 mid-Niigata Prefecture earthquake, will provide important information towards a better understanding of the generation of earthquakes and crustal deformations in the inverted back-arc rift basin. The special section in this issue of Earth, Planets and Space is a collection of papers on the 2007 Chuetsu-Oki Earthquake. Immediately after the earthquake, onshore and offshore seismic observations were made with densely distributed seismometers. The observations of aftershocks together with the data acquired by the permanent seismic networks enabled the source fault geometry and velocity structure to be delineated (Kato et al., 2008; Mori, 2008; Nakajima and Hasegawa, 2008; Shinohara et al., 2008;

Simulation of Seismicity in the Block-structure Model of Italy and its Surroundings

The numerical block-model of the lithosphere dynamics is used to simulate seismicity in Italy and its surroundings, based on the available structural and geodynamics information. The purpose of the study is to understand which are the tectonic processes that control the main features of the observed seismicity and the kinematics of the region. The influence of the rheology of the fault systems is studied as well. The model we use differs from other modeling approaches in that it simulates earthquakes and hence it possibly relates to seismicity and geodynamics. The model provides an effective capability to include the set of documented constraints supplied by widely available earthquake catalogs. This is done by means of the comparison of the GR relation, of the focal mechanisms and of the space distribution for observed and computed seismicity. The region is modeled as a system of perfectly rigid blocks, separated by infinitely thin fault planes, in viscoelastic interaction between themselves and with the underlying medium. The movement of the boundary blocks and of the underlying medium determines the motion of the blocks. The synthetic seismicity obtained with the defined block-model is similar to the observed one for the most seismically active areas. A linear frequency-magnitude (FM) relation (Gutenberg-Richter law) is obtained for synthetic earthquakes; the slope (b-value) of the FM plot appears larger for the synthetic seismicity than for the observed one. Nevertheless, the b-value is essentially larger in northern and central Italy than that in southern Italy, both in the model and in the observations. The analysis of the source mechanisms of the synthetic earthquakes shows a good agreement with the observations. In the model normal faulting is typical for the Apennines, the eastern edge of Sicily and the Calabrian arc, while reverse faulting takes place at the northwestern boundary of the Adriatic Sea, in the southern Alps and along the eastern edge of the Adria, along the Dinarides. The model correctly reproduces the extension zone along the Apennines and the contraction zone along the northwestern boundary of the Adriatic Sea; the counter-clockwise rotation of the Adria is mimed. The resulting movements of the blocks are in overall agreement with GPS (Global Positioning System) observations. The results of the modeling experiments suggest that the main features of dynamics and seismicity in the central Mediterranean region cannot be satisfactorily explained as a consequence of Africa and Eurasia convergence only; the passive subduction in the Calabrian arc and the different rheology of faults are essential as well.

Mantle flow-induced crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland (E Turkey) deduced from the geological and geophysical data

Eastern Anatolia consisting of an amalgamation of fragments of oceanic and continental lithosphere is a current active intercontinental contractional zone that is still being squeezed and shortened between the Arabian and Eurasian plates. This collisional and contractional zone is being accompanied by the tectonic escape of most of the Anatolian plate to the west by major strike-slip faulting on the right-lateral North Anatolian Transform Fault Zone (NATFZ) and left-lateral East Anatolian Transform Fault Zone (EATFZ) which meet at Karlıova forming an east-pointing cusp. The present-day crust in the area between the easternmost part of the Anatolian plate and the Arabian Foreland gets thinner from north (ca 44 km) to south (ca 36 km) relative to its eastern (EAHP) and western sides (central Anatolian region). This thinner crustal area is characterized by shallow CPD (12–16 km), very low Pn velocities (< 7.8 km/s) and high Sn attenuation which indicate partially molten to eroded mantle lid or occurrence of asthenospheric mantle beneath the crust. Northernmost margin of the Arabian Foreland in the south of the Bitlis–Pötürge metamorphic gap area is represented by moderate CPD (16–18 km) relative to its eastern and western sides, and low Pn velocities (8 km/s). We infer from the geophysical data that the lithospheric mantle gets thinner towards the Bitlis–Pötürge metamorphic gap area in the northern margin of the Arabian Foreland which has been most probably caused by mechanical removal of the lithospheric mantle during mantle invasion to the north following the slab breakoff beneath the Bitlis–Pötürge Suture Zone. Mantle flow-driven rapid extrusion and counterclockwise rotation of the Anatolian plate gave rise to stretching and hence crustal thinning in the area between the easternmost part of the Anatolian plate and the Arabian Foreland which is currently dominated by wrench tectonics.

Building bridges to 2020 and beyond: the road from Bali

What would the shape of a realistic, yet ambitious, package for the climate regime after 2012 look like? How do we obtain a package deal starting in Bali but building bridges to a post-2020 climate regime? A fair, effective, flexible and inclusive package deal has to strike a core balance between development and climate imperatives (mitigation, adaptation, dealing with the impacts of response measures, technology transfer, investment and finance) to create bargaining space and establish a conceptual contract zone. Within a continuum of possible packages, two packages in the contract zone are identified: ‘multi-stage’ and ‘ambitious transitional’. The latter is ambitious, combining domestic cap-and-trade for the USA, deeper cuts for Annex B countries, and quantifiable mitigation actions by developing countries. It is transitional as a possible bridge to a more inclusive regime beyond 2020. Multi-stage is defined around mechanisms by which countries move through increasingly stringent levels of participation, and must be based upon agreed triggers. Our assessment of political dynamics is that multi-stage is not yet in the political contract zone. Key to this is the absence of a ‘trigger from the North’, in that the largest historical emitter must act earlier and most decisively. But progress will also depend on continued leadership from Annex B countries, as well as more proactive, incentivized leadership in the South. Agreeing on the transitional stage is the critical next step in the evolution of the climate regime. Negotiating any package will require an institutional space for bargaining, political leadership and trust, and a clear time-frame.

Bargaining over an Uncertain Value: Arbitration Mechanisms Compared

This article explores the theoretical and behavioral impact of conventional arbitration and final-offer arbitration (FOA) when parties are bargaining over an uncertain value. In this context, one player receives a fixed payment while the other player receives the uncertain residual. Although both forms of arbitration have identically sized contract zones, we show theoretically that in FOA the contract zone shifts in favor of the residual claimant. In addition, as the variance of the possible values rises, the contract zone shifts further in favor of the residual claimant. In laboratory testing, the contract zone roughly reflects the central tendencies of behavior; however, both forms of arbitration increase conflict relative to a no-arbitration baseline. This is caused by residual claimants being more aggressive when arbitration is available while fixed-payment recipients are not. However, both parties play a role in the conflict escalation due to the increased proposal variation.

How powerful is arbitration procedure AFOA?

Recently, an amendment to final-offer arbitration (AFOA) was proposed to improve the well-known final-offer arbitration (FOA): AFOA is powerful enough to overcome the uncertainty about the arbitrator’s notion of a fair settlement, if both disputants are risk neutral. This paper further examines the behavior of AFOA when two disputants are not risk neutral, by use of an existing concept of contract zone and a newly proposed concept of convergent-offer zone. The result is that AFOA is riskier than other existing procedures, therefore more powerful to induce an agreement between risk-averse disputants.

Scour in Long Contractions

Experimental results on local scour in long contractions for uniform and nonuniform sediments (gravels and sands) under clear-water scour are presented. An emphasis was given to conduct the experiments on scour in long contractions for gravels. The findings of the experiments are used to describe the effects of various parameters (obtained from dimensional analysis) on equilibrium scour depth under clear-water scour. The equilibrium scour depth increases with decrease in opening ratio and with increase in sediment size for gravels. But the curves of scour depth versus sediment size have considerable sag at the transition of sand and gravel. The scour depth decreases with increase in densimetric Froude number, for larger opening ratios, and increases with increase in approaching flow depth at lower depths. However, it becomes independent of approaching flow depth at higher flow depths. The effect of sediment gradation on scour depth is pronounced for nonuniform sediments, which reduce scour depth significantly due to the formation of armor layer in the scour hole. Using the continuity and energy equations, a simple analytical model for the computation of clear-water scour depth in long contractions is developed with and without sidewall correction for contracted zone. The models agree satisfactorily with the present and other experimental data. Also, a new empirical equation of maximum equilibrium scour depth, which is based on the experimental data at the limiting stability of sediments in approaching channel under clear-water scour, is proposed. The potential predictors of the maximum equilibrium scour depth in long contractions are compared with the experimental data. The comparisons indicate that the equations given by Komura and Lim are the best predictors among those examined.

Physiology of the esophageal pressure transition zone: separate contraction waves above and below

Manometrically measured peristaltic pressure amplitude displays a well-defined trough in the upper esophagus. Whereas this manometric "transition zone" (TZ) has been associated with striated-to-smooth muscle fiber transition, the underlying physiology of the TZ and its role in bolus transport are unclear. A computer model study of bolus retention in the TZ showed discoordinated distinct contraction waves above and below. Our aim was to test the hypothesis that distinct upper/lower contraction waves above/below the manometric TZ are normal physiology and to quantify space-time coordination between tone and bolus transport through the TZ. Eighteen normal barium swallows were analyzed in 6 subjects with concurrent 21-channel high-resolution manometry and digital fluoroscopy. From manometry, the TZ center (nadir pressure amplitude) and the upper/lower margins of the pressure trough were objectively quantified. Using fluoroscopy, we quantified space-time trajectories of the bolus tail and bolus tail pressures and maximum intraluminal pressures proximal to the tail with their space-time trajectories. In every swallow, the bolus tail followed distinct trajectories above/below the TZ, separated by a well-defined spatial "jump" that terminated an upper contraction wave and initiated a lower contraction wave (3.32 +/- 1.63 cm, P = 0.0004). An "indentation wave" always formed within the TZ distal to the upper wave, increasing in amplitude until the lower wave was initiated. As the upper contraction wave tail entered the TZ, it slowed and the tail pressure reduced rapidly, while indentation wave pressure increased to normal tail pressure values at the initiation of the lower wave. The TZ was a special zone of segmental contraction. The TZ is, physiologically, the transition from an upper contraction wave originating in the proximal striated esophagus to a lower contraction wave that moves into the distal smooth muscle esophagus. Complete bolus transport requires coordination of upper/lower waves and sufficient segmental squeeze to fully clear the bolus from the TZ during the transition period.

Strain concentration zone along the volcanic front derived by GPS observations in NE Japan arc

A nationwide GPS array with more than 1,000 permanent stations operated by the Geographical Survey Institute of Japan, has provided many invaluable deformation data such as co- and post-seismic, volcanic, and ongoing secular deformations in the Japanese islands. Based on daily coordinate data of the GEONET stations together with results from a regional network operated by Tohoku University, we derived a map of the strain rate distribution in NE Japan showing that there exists a notable strain concentration zone of EW contraction along the Volcanic Front. The area demonstrates active seismicity including some disastrous earthquakes. Recent seismic tomography studies have revealed the existence of inclined seismic low-velocity zones (LVZ) at depths shallower than ~150 km in the mantle wedge sub-parallel to the subducted slab. The inclined LVZ reaches the Moho right beneath the Volcanic Front, indicating that the formation of the strain concentration zone is closely related to the rheological structure of the island-arc system.

The SACU‐US free trade agreement: In search of a contract zone

The issues in the negotiations between the Southern African Customs Union (SACU) and the US for a free trade area are complex and difficult. This article looks at whether there is room for sufficient trade offs to enable a successful conclusion to the process.

A Comparison of Arbitration Procedures for Risk‐Averse Disputants*

ABSTRACTWe propose an arbitration model framework that generalizes many previous quantitative models of final offer arbitration, conventional arbitration, and some proposed alternatives to them. Our model allows the two disputants to be risk averse and assumes that the issue(s) in dispute can be summarized by a single quantifiable value. We compare the performance of the different arbitration procedures by analyzing the gap between the disputants' equilibrium offers and the width of the contract zone that these offers imply. Our results suggest that final offer arbitration should give results superior to those of conventional arbitration.

Pretrial settlement with fairness

We introduce fairness into three models of pretrial settlement and find that it increases the incidence of trial in each. A taste for fairness is reflected in the percentage of their own trial costs a party is willing to give up in accepting a pretrial offer. In models of asymmetric information, a taste for fairness lowers the cost of a rejected offer and so increases the incidence of trial. In an optimism model, a taste for fairness increases the probability that a contract zone will fail to exist, and thereby increases the incidence of trial.

The Eocene Southern Vancouver Island Orocline — a response to seamount accretion and the cause of fold-and-thrust belt and extensional basin formation

A deflection of the fault controlled southwestern coastline of Vancouver Island suggests the presence of a minor orocline, with a Southern Crustal Block (south of Barkley Sound–Alberni Inlet) rotated 20° counterclockwise relative to a Northern Fixed Crustal Block about a pole of rotation located northeast of Port Alberni. In this paper two models of orocline development, one of pure block rotation and one of pure bending, are proposed. The predictions of these models are tested against available geological maps, structural orientation data, identified regions of extension and contraction, and paleomagnetic data. Structural orientation and paleomagnetic data are consistent with 18° of post-Late Cretaceous counter clockwise rotation of the Southern Crustal Block relative to the Northern Fixed Crustal Block. A southward increase in the magnitude of rotation evident in the structural orientation data argues for a model of bending. Both bending and block rotation models predict the development of a zone of contraction along the northeast margin of the Southern Crustal Block, coincident with the location of the Eocene Cowichan fold-and-thrust belt, that diminishes northward toward the pole of rotation. As predicted, the fold-and-thrust belt is characterized by a northerly decrease in the amount of shortening, from >30% at the south end of the thrust belt, to 0% shortening north of Port Alberni. The northerly decrease in shortening is complemented by a north to south change in structural style from cylindrical to conical folds, and finally to planar, undeformed strata. The model of block rotation predicts the presence of a zone of extension extending southwest from the zone of rotation, coincident with the location of Eocene extensional structures within Barkley Sound and with horst and graben structures in the offshore Eocene to Miocene Tofino basin. Extension is less than predicted by a model of pure block rotation and suggests that much of the oroclinal rotation was accommodated by bending. Timing constraints indicate that orocline development was coeval with, and resulted from, the Eocene accretion of seamounts of the Crescent terrane. These findings demonstrate that oroclinal orogeny, the buckling of a linear crustal beam about vertical axes of rotation, can significantly impact the geometry, structure and character of an orogenic belt, even where the buckles are minor (<20° of rotation).

Illustrated Examples of the Effects of Risk Preferences and Expectations on Bargaining Outcomes

The author highlights bargaining examples that use expected utility theory. Bargainer payoffs in the event of a dispute are represented by a simple lottery. Expectations are assumed to affect a bargainer's subjective probabilities over lottery outcomes, and risk preferences affect the expected utility of a given lottery. Risk preferences and/or expectations are predicted to influence both negotiated outcomes and the likelihood of a bargaining impasse. The analysis shows that, ceteris paribus, risk aversion or pessimism, or both, will cause a bargainer to capture less of the pie in negotiations. Similarly, risk-loving and optimistic bargainers are more likely to experience impasse because of the disappearance of the contract zone. The results are intuitive, can be shown graphically and algebraically, and provide upper-level students with engaging examples that show the usefulness of expected utility theory.

The role of deformation in controlling depositional patterns in the south-central Niger Delta, West Africa

The Niger Delta has a distinctive structural and stratigraphic zonation. Regional and counter-regional growth faults, developed in an outer-shelf and upper-slope setting, are linked, via a translational zone containing shale diapirs, to a contractional zone defined by a fold-thrust belt that developed in a toe-of-slope setting. Structural and depositional systems have migrated with the progradation of the delta. A paleo fold belt is buried under the modern upper/middle slope. The structural system in this paleo fold belt is complex and comprises a series of en échelon thrust-cored folds and associated ponded slope-basins, shale diapirs, and extensional growth faults. Analysis of the growth sections filling the ponded slope-basins provides a record of how this accommodation was created and subsequently filled and how the individual structural elements interact to create and modify the available space. The depositional systems initially exploit primary accommodation on the slope created by structural movement—the synchronous growth of the fold, the extensional faults and the shale diapir. As the pond is progressively filled, the previously deposited strata modify the accommodation and subsequent depositional systems compensate accordingly.

The mechanical advantage of local longitudinal shortening on peristaltic transport.

Whereas bolus transport along the esophagus results from peristaltic contractions of the circular muscle layer, it has been suggested that local shortening of the longitudinal muscle layer concentrates circular muscle fibers in the region where the highest contractile pressures are required. Here we analyze the mechanical consequences of local longitudinal shortening (LLS) through a mathematical model based on lubrication theory. We find that local pressure and shear stress in the contraction zone are greatly reduced by the existence of LLS. In consequence, peak contractile pressure is reduced by nearly 2/3 at physiological LLS, and this reduction is greatest when peak in LLS is well aligned with peak contractile pressure. We conclude that a peristaltic wave of local longitudinal muscle contraction coordinated with the circular muscle contraction wave has both a great physiological advantage (concentrating circular muscle fibers), and a great mechanical advantage (reducing the level of contractile force required to transport the bolus), which combine to greatly reduce circular muscle tone during esophageal peristalsis.

Tectonic stress state in NE Japan as part of the Okhotsk plate

An existing geodetic flow velocity model, obtained by using an internal free network adjustment technique, is used to derive estimates for various strain rates parameters in NE Japan. The greatest shortening rates of the principal strains, trending ∼E–W, are located in regions where much steady, internal, frame-invariant plastic flow deformation is observed to be taking place. The internal geodetic adjustment technique yielded the internal deformation in the Tohoku arc; most of the intraplate deformations, including the much folding deformations observed in the inner zone, are produced from within. An interseismic transient elastic loading at a strongly coupled/locked Japan trench would not be needed. The observed ongoing extensive ductile folding deformation in the inner zone of Tohoku may mean that the geodetic strain rates, causing shortening at ∼2–3 cm/yr, probably reflect the more correct level of the deformation, which is steady/permanent, in NE Japan as compared with seismic/faulting data, which indicate ∼0.5 cm/yr shortening. The calculated principal strain rates are used to make an interpretation for the origin of the deviatoric principal stresses within the greater regional plate tectonic framework. The tectonic stress state in NE Japan, as part of the Okhotsk plate, could mostly be influenced by the Okhotsk plate, which is extruding southward to lessen the significant accumulated contractional deformation in NE Asia in the Verkhoyansk–Cherskii mountains. The principal strain rates are ∼N–S extensional essentially everywhere in NE Japan, as a result of the southerly extrusion, except in its southernmost leading edge, in the Uetsu/Fossa Magna province, where the Japan Alps rampart rises in front of the extrusion. Here an ∼E–W compressional stress state prevails. A second ∼E–W contractional zone is found in north-central Tohoku, extending from the Sanriku province in the outer zone to the inner zone in the Japan Sea side, being more prevalent in the latter zone. The calculated rotation rates from the geodetic flow model are clockwise (CW) in both of the ∼E–W contractional regions. NE Japan, extruding southward, faces buttresses in (1) the Oga–Ojika Line (OOL), and/or a crustal weakness zone between the northern and the southern halves of Tohoku approx. at ∼38.5°N latitude, and, especially, (2) the Japanese Alps rampart; these obstacles cause the northern and southernmost Tohoku to veer to its right and rotate CW, thereby setting up the ∼E–W-trending compressional deformation in their respective inner zones. Between the OOL (or the 38.5°N boundary) and the Kanto Tectonic Line (KTL), the sense of the differential rotations is counterclockwise (CCW), towards the ocean to the SE. The northern Tohoku (north of the OOL) and the southernmost Tohoku (south of the KTL) cannot rotate CCW towards the ocean because of the Izu block's collision in the south and the relatively strong coupling along the subduction interface beneath the Japan trench in the north off-Sanriku. The relatively stronger long-term coupling between the northern Tohoku and the Pacific plate at the Sanriku coast, with respect to that in off-Fukushima, is due to a flatter subduction of the Pacific slab there, increasing the plates’ interface contact area; the flattening of the subduction dip angle was caused by CCW rotation and shifting of the northern Tohoku along the dextral Honjo–Matsushima Line, roughly corresponding to the OOL, towards the Pacific and overriding of the subduction zone during the formation of the Japan Sea.

New evidence for Cretaceous strike-slip faulting in the United States Cordillera and implications for terrane-displacement, deformation patterns, and plutonism

Early to mid-Cretaceous dextral strike-slip faulting, involving up to 400 km displacement, has been documented in the southern Sierra Nevada of California.In western Idaho, the Salmon River suture juxtaposes unrelated oceanic and continental rocks along a major, near-vertical shear zone that was active in the Early to mid-Cretaceous. These two structural zones have been treated as separate entities; however, new data indicate that they likely connect via a structural discontinuity in northwest Nevada and southeast Oregon, herein called the western Nevada shear zone (WNS). Current structures within the WNS record dip-slip contractional deformation; however, regional relations (structural and stratigraphic) indicate a mismatch in the early Mesozoic geology of rocks across the WNS that is best explained by dextral strike-slip displacement of several 100 km. These relations argue that an early strike-slip structure along the WNS was reactivated and obscured during later regional shortening deformation, most likely related to the Cretaceous Sevier orogeny. The WNS is along strike and broadly coeval with the Salmon River suture zone and strike-slip boundaries in the Sierra Nevada. We hypothesize that all these features are related elements of a major structural boundary in the western United States Cordillera. This boundary is interpreted to have accommodated significant dextral strike-slip displacement of outboard arc terranes of the Cordillera in the Early Cretaceous, followed by reactivation as a localized contractional zone in the mid-Cretaceous during the Sevier orogeny. Cretaceous batholiths of the United States Cordillera closely parallel the boundary, which we suggest formed a major crustal flaw that localized and facilitated emplacement of arc magmas.