Search

I. INTRODUCTION II. BACKGROUND III. SECTION 10 OF THE RIVERS AND HARBORS ACT AS A POTENTIAL BASIS FOR AUTHORITY A. Courts Have Embraced Section 10's Upland Jurisdiction B. The Corps' [...], A growing body of science links hydraulic fracturing (fracking) to damage-causing earthquakes. Scientists and citizen groups fear these earthquakes could critically damage public civil works projects--e.g., dams, locks, and levees--that provide economic, environmental, and recreational benefits to the United States. This Comment argues that the U.S. Army Corps of Engineers (Corps), as caretaker of these public civil works projects and their associated navigable waters, has sufficient legal authority under section 10 of the Rivers and Harbors Act to manage the alleged risks. This Comment analyzes how section 10 has been successfully applied to regulate activities that, like fracking, take place outside of navigable waterways yet threaten the navigable capacity of U.S. waters. This Comment maintains that pursuant to section 10, the Corps could subject certain fracking operations to its existing permit program and seek to enjoin other similar operations. After acknowledging likely resistance to what would be an expansion of federal control over fracking, this Comment concludes that section 10 provides a strong legal foundation upon which the Corps could take action to protect its civil works projects from threats posed by fracking-caused earthquakes.

The creation of ocean crust by rapid injection of magma at mid-ocean ridges can lead to eruptions of lava onto the seafloor and release of 'event plumes,' which are huge volumes of anomalously warm water enriched in reduced chemicals that rise up to 1 km above the seafloor. Here, we use seismic data to show that seafloor eruptions and the release of hydrothermal event plumes correspond to diking episodes with high injection velocities and rapid onset of magma emplacement within the rift zone. These attributes result from high excess magma pressure at the dike source, likely due to a new influx of melt from the mantle. These dynamic magmatic conditions can be detected remotely and may predict the likelihood of event plume release during future seafloor spreading events. Keywords: dike injection, earthquakes, hydroacoustics, ridge, Juan de Fuca.

[1] The 1897 Shillong (Assam), northeast India, earthquake is considered to be one of the largest in the modern history. Although Oldham's [1899] classic memoir on this event opened new vistas in observational seismology, many questions on its style of faulting remain unresolved. Most previous studies considered this as a detachment earthquake that occurred on a gently north dipping fault, extending from the Himalayan front. A recent model proposed an alternate geometry governed by high-angle faults to the north and south of the plateau, and it suggested that the 1897 earthquake occurred on a south dipping reverse fault, coinciding with the northern plateau margin. In this paper, we explore the available database, together with the coseismic observations from the region, to further understand the nature of faulting. The geophysical and geological data examined in this paper conform to a south dipping structure, but its location is inferred to be in the Brahmaputra basin, further north of the present plateau front. Our analyses of paleoseismic data suggest a 1200-year interval between the 1897 event and its predecessor, and we identity the northern boundary fault as a major seismic source. The Shillong Plateau bounded by major faults behaves as an independent tectonic entity, with its own style of faulting, seismic productivity, and hazard potential, distinct from the Himalayan thrust front, a point that provides fresh insight into the regional geodynamics. INDEX TERMS: 7209 Seismology: Earthquake dynamics and mechanics; 7215 Seismology: Earthquake parameters; 7221 Seismology: Paleoseismology; 7230 Seismology: Seismicity and seismotectonics; 7299 Seismology: General or miscellaneous; KEYWORDS: earthquake, tectonics, paleoseismology, faulting, seismicity, northeast India. Citation: Rajendran, C.P., K. Rajendran. B. P. Duarah, S. Baruah. and A. Earnest (2004), Interpreting the style of faulting and paleoseismicity associated with the 1897 Shillong, northeast India, earthquake: Implications for regional tectonism, Tectonics, 23, TC4009, doi: 10.1029/2003TC001605.

Triggering of earthquakes by filling of artificial water reservoirs is known for over six decades. As of today, over 90 sites have been globally identified where earthquakes have been triggered by filling of water reservoirs. The question of earthquakes triggered by artificial reservoirs has been addressed and reviewed in a number of papers and books. In the present review, the book 'Reservoir-Induced Earthquakes' by Gupta [Gupta, H.K., 1992. Reservoir-Induced Earthquakes. Elsevier, Amsterdam, 364 pp.], which contains all the necessary information on this topic till 1990, has been taken as the base. An effort has been made to add information on this important topic gathered over the last 10 years. Koyna, India continues to be the most significant site of artificial-water-reservoir-triggered earthquakes. During 1990s, two events exceeding M 5 and several smaller events occurred in the vicinity of Koyna, and recently impounded Warna Reservoir. Detailed studies have addressed the relocation of earthquakes, stress drop, nucleation, migration and other important aspects of these earthquakes. In a unique experiment, twenty-one 90- to 250-m deep borewells have been drilled in the seismically active Koyna-Warna region and the water levels are continuously monitored. Step-like coseismic changes of several centimeters have been observed in some wells associated with a few M [greater than or equal to] 4 events. Detailed tomographic studies conducted on one of the best recorded triggered earthquake sequence at Lake Oroville in California revealed that this sequence was associated with a southwest dipping structure characterized by low velocity, while in adjacent areas, seismic activity occurs in regions of higher velocity. Similar investigations in Aswan showed that shallow activity is associated with low P-wave velocity. Several new reservoir sites that have triggered earthquakes have been reported during 1990s. The most important being Srinagarind Dam in Thailand, which had an M 5.9 earthquake and the sequence had all the characteristics of triggered earthquake sequences. New theoretical work, particularly the effect of pore fluid pressure in anisotropic rocks and its implication in triggered seismicity is an important development. However, much more needs to be done to fully comprehend the role of artificial water reservoirs in triggering earthquakes. Keywords: triggered earthquakes; artificial water reservoirs; pore pressure; earthquake nucleation

The Helice earthquake of 373 B.C. ruptured the master fault of the Gulf of Corinth but the antithetic fault at Delphi. The famous oracular cave of this region may have been an ancient tectonic rupture.

A band of seismicity transects the southern Sierra Nevada range between the northeastern end of the site of the 1952 [M.sub.W] (moment magnitude) 7.3 Kern County earthquake and the site of the 1946 [M.sub.W] 6.1 Walker Pass earthquake. Relocated earthquakes in this band, which lacks a surface expression, better delineate the northeast-trending seismic lineament and resolve complex structure near the Walker Pass mainshock. Left-lateral earthquake focal planes are rotated counterclockwise from the strike of the seismic lineament, consistent with slip on shear fractures such as those observed in the early stages of fault development in laboratory experiments. We interpret this seismic lineament as a previously unrecognized, incipient, currently blind, strike-slip fault, a unique example of a newly forming structure.

Circumstantial and physical evidence indicates that the 1997 [M.sub.w] 4.9 earthquake in southern Alabama may have been related to hydrocarbon recovery. Epicenters of this earthquake and its aftershocks were located within a few kilometers of active oil and gas extraction wells and two pressurized injection wells. Main shock and aftershock focal depths (2-6 km) are within a few kilometers of the injection and withdrawal depths. Strain accumulation at geologic rates sufficient to cause rupture at these shallow focal depths is not likely. A paucity of prior seismicity is difficult to reconcile with the occurrence of an earthquake of [M.sub.w] 4.9 and a magnitude-frequency relationship usually assumed for natural earthquakes. The normal-fault main-shock mechanism is consistent with reactivation of preexisting faults in the regional tectonic stress field. If the earthquake were purely tectonic, however, the question arises as to why it occurred on only the small fraction of a large, regional fault system coinciding with active hydrocarbon recovery. No obvious temporal correlation is apparent between the earthquakes and recovery activities. Although thus far little can be said quantitatively about the physical processes that may have caused the 1997 sequence, a plausible explanation involves the poroelastic response of the crust to extraction of hydrocarbons.

Seismic tomography revealed a low seismic velocity (-5%) and high Poisson's ratio (+6%) anomaly anomaly covering about 300 square kilometers at the hypocenter of the 17 January 1995, magnitude 7.2, Kobe earthquake in Japan. This anomaly may be due to an overpressurized, fluid-filled, fractured rock matrix that contributed to the initiation of the Kobe earthquake., The 17 January 1995, magnitude (M) 7.2, Kobe (Hyogo-Ken Nanbu) earthquake was the most damaging earthquake to strike Japan since the Kanto earthquake in 1923 (1). The Kobe earthquake occurred [...]

Nonvolcanic tremors occur adjacent to rocked faults and may be closely related to the generation of earthquakes. Monitoring of the San Andreas Fault in the Parkfield, California, region revealed that after two strong earthquakes, tremor activity increased in a hearty dormant tremor zone, increased and became periodic in a previously active zone, and has remained elevated and periodic for over 4 years. Static shear- and Coulomb-stress increases of 6 to 14 kilopascals from these two earthquakes are coincident with sudden increases in tremor rates. The persistent changes in tremor suggest that stress is now accumulating more rapidly beneath this part of the San Andreas Fault, which ruptured in the moment magnitude 7.8 Ft. Tejon earthquake of 1857.

Geodetic observations of crustal motions in the Tonga Lau system, using the Global Postioning System, suggest that the intense magnetic seismicity in the region can be attributed to high subduction and back-arc extension rates. The opening rate of the Lau basin increases northward up to nearly 60 mm per year. The northern Tonga ridge contains part of a rigid microplate, as suggested by the absence of straining in the region. Convergence rates across the Tonga increases northward up to nearly 240 mm per year.

Laboratory experiments indicate that the overpressuring of fluids in geological faults can bring on the slippage that results in earthquakes. These overpressured fluids could diminish the shear stress needed to make the faults slide through a two-step process: sealing and compaction. Sealing blocks the movement of fluids from the fault zone to the adjacent rock and compaction of the fault rock allows slippage by increasing pore pressure in the sealed fault.

The research findings on seven major earthquakes, which had rocked Turkey since 1992, reveals that, absence of interior reinforced-concrete walls, lead to the collapse of most of the school buildings. The research was conducted separately by universities in Turkey and United States.

Examination of the Serghaya fault, a branch of the Dead Sea Fault System in western Syria and eastern Lebanon, documents Late Quaternary and Recent left-lateral fault movements including the probable remnant of a historic coseismic surface rupture. Carbon-14 dating and the presence of fault-scarp free faces in soft, late Pleistocene lake deposits suggest coseismic slip during the past two or three centuries, possibly corresponding with one of the well-documented earthquakes of 1705 or 1759. With an estimated Holocene slip rate of 1-2 mm [a.sup.-1], the Serghaya Fault accommodates a significant part of the active deformation along the Arabian-African plate boundary. These results suggest that multiple active fault branches are involved in the transfer of strain through the `Lebanese' restraining bend. Keywords: Dead Sea Transform, Syria, Lebanon, neotectonics, earthquakes.

In a number of subduction zones, earthquakes at 50-200 km depth define two dipping planes, separated by 20-40 km, that appear to merge downdip. Upper plane earthquakes are inferred to occur within the subducting oceanic crust, whereas lower plane earthquakes occur in the subducting oceanic mantle. Beneath northeast Japan, the results of a new finite-element heat-transfer model suggest that the lower seismic plane cuts across isotherms at a shallow angle. Lower plane earthquakes occur at ~550-800 [degrees] C at 100 km depth and at ~350-600 [degrees] C at 160 km depth. These conditions coincide with the dehydration reaction antigorite (serpentine) [right arrow] forsterite + enstatite + [H.sub.2]O, which suggests that lower plane earthquakes may be triggered by dehydration embrittlement, which in turn suggests that the subducting oceanic mantle is partially hydrated. Serpentinization may occur in the trench--outer rise region, where faulting may promote infiltration of seawater several tens of kilometers into the oceanic lithosphere. If this hypothesis is correct, current subduction-zone [H.sub.2]O budgets may significantly underestimate the amount of bound [H.sub.2]O entering the 'subduction factory.' Keywords: dehydration, earthquakes, metamorphism, serpentine, subduction zone.

Several large and enigmatic earthquakes have occurred in the interior of tectonic plates, far from stresses that arise at the boundaries between plates. In some cases--particularly in Scandanavia and perhaps [...]

Stress measurements in deep boreholes have universally shown that stresses in the Earth's crust are in equilibrium with favorably oriented faults with friction coefficients in the range 0.6--0.7 and with nearly hydrostatic pore-pressure gradients. Because of the lack of any fault-adjacent heat-flow anomaly as predicted by a conductive model of frictional heating, the San Andreas fault has long been thought to be an exception, i.e., far weaker than this standard case. Borehole stress measurements near the San Andreas fault have failed to confirm this weak-fault hypothesis, being either inconclusive or in conflict with it. Directions of maximum horizontal stresses reported to be nearly fault normal in central California are now known not to be regional stresses but a result of active folding within folds that have been rotated 20 [degrees]-30 [degrees] clockwise from their original orientations. Everywhere in southern California it is observed that the maximum stress directions rotate to smaller angles (30 [degrees]-60 [degrees]) with the San Andreas, within 20 km of it. The sense of this rotation is opposite to that expected from the weak-fault hypothesis and indicates that the shear stress on the San Andreas is comparable in magnitude to all other horizontal stresses in the system. In the 'big bend' section of the fault, this rotation is predicted from a transpressional plate-boundary model in which the San Andreas is loaded by a deep shear zone with a locking depth of 10 km. If the adjacent minor thrust faults are assumed to obey Byerlee friction, the crustal-average shear stress on the San Andreas in that region must be in the range 100-160 MPa, regardless of the pore pressure in the fault. These stresses are many times greater than permitted by the weak-fault hypothesis. In the more transcurrent regions farther south, the San Andreas shear stress will be smaller than this estimate, but similar stress rotations observed there indicate that the San Andreas cannot be weak relative to minor faults in that region. These stress rotations can only be consistent with the weakfault hypothesis if it were assumed that all faults in California were equally weak, which is known to be untrue. The conclusion is that the heat-flow model is flawed, probably in its assumption that all heat transfer is governed by conduction. Keywords: San Andreas fault, fault strength, faults, strength, stress, earthquakes.

A study is conducted in Joes Valley Dam to investigate the effects of nearby coal mining on earthquake risk in the area. Seismologists from the University of Utah, the U.S. Geological Survey (USGS), and the U.S. Bureau of Reclamation studied earthquakes within the Trail Mountain Mine, adjacent to the tract where future coal mining is planned might get an earthquake as large as magnitude 3.9 at the dam.

According to a new research melting of glaciers could cause earthquakes in Southern Alaska. The new research links ice mass changes caused by glacial thinning to an increase in local seism city and the occurrence of past earthquakes.

Research presented concerns the slip rate, or fault movement, of the Reelfoot Lake blind-thrust fault in the Mississippi Valley. Topics addressed include the geological factors affecting earthquake magnitude and destruction levels in the New Madrid seismic zone, and the US Geological Survey's earthquake forecasts for the area.

Seismicity is correlated in space and time with production from some oil and gas fields where pore pressures have declined by several tens of megapascals. Reverse faulting has occurred both above and below petroleum reservoirs, and normal faulting has occurred on the flanks of at least one reservoir. The theory of poroelasticity requires that fluid extraction locally alter the state of stress. Calculations with simple geometries predict stress perturbations that are consistent with observed earthquake locations and focal mechanisms. Measurements of surface displacement and strain, pore pressure, stress, and poroelastic rock properties in such areas could be used to test theoretical predictions and improve our understanding of earthquake mechanics.

In spite of extensive research, the causal structure of the 1886 magnitude 7 earthquake near Charleston, South Carolina, has not bee identified. In this study I analyzed digital surface topography and river morphology in light of earlier studies using seismic reflection, seismic refraction, earthquake seismology, and gravity and magnetic surveys. This analysis revealed an area approximately 400 [km.sup.2] northwest of Charieston that may have been repeatedly uplifted by earthquakes. Geologica and seismic reflection data confirm alteration of formations at depth. Deformation of the surface is supported by observations on aerial and LANDSAT photographs. Therefore, the structure on which the 1886 earthquake occurred may be within the uplifted area defined in this report.

One of the first things taught in elementary physics is that friction increases with the force applied perpendicular to a sliding surface (the normal force). As innumerable high school experiments […]

Large earthquakes are possibly caused due to shearing of isolated mountains (seamounts) in subduction zones of the ocean. The position of seamount decapitation determines the magnitude of the earthquake. Asperities are strong areas of the plate interface that control earthquake occurrences. They are made from the subducted seamounts and are affected by sea floor roughness and style of sediment subduction. The size of earthquakes varies between subduction zones probably due to the absolute velocity of the overlying plate that affects the speed of subduction.

Research at the Transverse Ranges shows that the Pacific and North American tectonic plates collide because of a kink in the San Andreas fault. Earthquakes are inevitable in the region as the bend in the strike-slip fault does not allow the two plates to slide past each other. Researchers can monitor the speed of seismic waves caused by the subduction. The Transverse Ranges cross the San Andreas fault in the Big Bend region.

Some subduction zones are seismically active and cause earthquakes, while some others are quiescent. The Cascadia subduction zone, which extends along the coast from northern California to southern British Columbia, is one such area which has geological evidence of possible earthquakes. Tichelaar, Ruff, Hyndman and Wang attempted to discover the reason for the lack of earthquakes in this region in recent times. They suggest the narrow seismic zone as a possible reason.

The article discusses the devastating earthquake of June7, 1692, which completely destroyed the bustling town of Port Royal, Jamaica, is described. The town's inhabitants and building sank as the sand beneath Port Royal liquefied and turned into roiling quicksand wiping away all evidence of its prosperous past.