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What is paleoflood hydrology? How are paleofloods analyzed? What are common paleoflood results? What are the implications of paleoflood analyses?

We present a detailed example of how a subbasin develops adjacent to a transfer zone in the Rio Grande rift. The Embudo transfer zone in the Rio Grande rift is considered one of the classic examples and has been used as the inspiration for several theoretical models. Despite this attention, the history of its development into a major rift structure is poorly known along its northern extent near Taos, New Mexico. Geologic evidence for all but its young rift history is concealed under Quaternary cover. We focus on under­standing the pre-Quaternary evidence that is in the subsurface by integrating diverse pieces of geologic and geophysical information. As a result, we present a substantively new understanding of the tectonic configuration and evolution of the northern extent of the Embudo fault and its adjacent subbasin. We integrate geophysical, borehole, and geologic information to interpret the subsurface configuration of the rift margins formed by the Embudo and Sangre de Cristo faults and the geometry of the subbasin within the Taos embayment. Key features interpreted include (1) an imperfect D-shaped subbasin that slopes to the east and southeast, with the deepest point ∼2 km below the valley floor located northwest of Taos at ∼36° 26′N latitude and 105° 37′W longitude; (2) a concealed Embudo fault system that extends as much as 7 km wider than is mapped at the surface, wherein fault strands disrupt or truncate flows of Pliocene Servilleta Basalt and step down into the subbasin with a minimum of 1.8 km of vertical displacement; and (3) a similar, wider than expected (5–7 km) zone of stepped, west-down normal faults associated with the Sangre de Cristo range front fault. From the geophysical interpretations and subsurface models, we infer relations between faulting and flows of Pliocene Servilleta Basalt and older, ­buried basaltic rocks that, combined with geologic mapping, suggest a revised rift history involving shifts in the locus of fault activity as the Taos subbasin developed. We speculate that faults related to north-striking grabens at the end of Laramide time formed the first west-down master faults. The Embudo fault may have initiated in early Miocene southwest of the Taos region. Normal-oblique slip on these early fault strands likely transitioned in space and time to dominantly left-lateral slip as the Embudo fault propagated to the northeast. During and shortly after eruption of Servilleta Basalt, proto-­Embudo fault strands were active along and parallel to the modern, NE-aligned Rio Pueblo de Taos, ∼4–7 km basinward of the modern, mapped Embudo fault zone. Faults along the northeastern subbasin margin had northwest strikes for most of the period of subbasin formation and were located ∼5–7 km basinward of the modern Sangre de Cristo fault. The locus of fault activity shifted to more northerly striking faults within 2 km of the modern range front sometime after Servilleta volcanism had ceased. The northerly faults may have linked with the northeasterly proto-Embudo faults at this time, concurrent with the development of N-striking Los Cordovas normal faults within the interior of the subbasin. By middle Pleistocene(?) time, the Los Cordovas faults had become inactive, and the linked Embudo–Sangre de Cristo fault system migrated to the south, to the modern range front.

Stress changes produced by the 1906 San Francisco earthquake had a profound effect on the seismicity of the San Francisco Bay region (SFBR), dramatically reducing it in the twentieth century. Whether the SFBR is still within or has emerged from this seismic quiescence is an issue of debate with implications for earthquake mechanics and seismic hazards. Historically, the SFBR has not experienced one complete earthquake cycle (i.e., the accumulation of stress, its release primarily as coseismic slip during surface‐faulting earthquakes, its re‐accumulation in the interval following, and its subsequent rerelease). The historical record of earthquake occurrence in the SFBR appears to be complete at about M 5.5 back to 1850 (Bakun, 1999). For large events, the record may be complete back to 1776, which represents about half a cycle. Paleoseismic data provide a more complete view of the most recent pre‐1906 SFBR earthquake cycle, extending it back to about 1600. Using these, we have developed estimates of magnitude and seismic moment for alternative sequences of surface‐faulting paleoearthquakes occurring between 1600 and 1776 on the region’s major faults. From these we calculate seismic moment and moment release rates for different time intervals between 1600 and 2012. These show the variability in moment release and suggest that, in the SFBR regional plate boundary, stress can be released on a single fault in great earthquakes such as that in 1906 and in multiple ruptures distributed on the regional plate boundary fault system on a decadal time scale.

Tectonic deformation from the 2010 Maule (Chile) Mw 8.8 earthquake included both uplift and subsidence along about 470 km of the central Chilean coast. In the south, deformation included as much as 3 m of uplift of the Arauco Peninsula, which produced emergent marine platforms and affected harbor infrastructure. In the central part of the deformation zone, north of Constitución, coastal subsidence drowned supratidal floodplains and caused extensive shoreline modification. In the north, coastal areas experienced either slight uplift or no detected change in land level. Also, river-channel deposition and decreased gradients suggest tectonic subsidence may have occurred in inland areas. The overall north-south pattern of 2010 coastal uplift and subsidence is similar to the average crestal elevation of the Coast Range between latitudes 33°S and 40°S. This similarity implies that the topography of the Coast Range may reflect long-term permanent strain accrued incrementally over many earthquake cycles.

SUMMARY The Mw 8.8 Maule earthquake occurred off the coast of central Chile on 2010 February 27 and was the sixth largest earthquake to be recorded instrumentally. This subduction zone event was followed by thousands of aftershocks both near the plate interface and in the overriding continental crust. Here, we report on a pair of large shallow crustal earthquakes that occurred on 2010 March 11 within 15 min of each other near the town of Pichilemu, on the coast of the O’Higgins Region of Chile. Field and aerial reconnaissance following the events revealed no distinct surface rupture. We infer from geodetic data spanning both events that the ruptures occurred on synthetic SW-dipping normal faults. The first, larger rupture was followed by buried slip on a steeper fault in the hangingwall. The fault locations and geometry of the two events are additionally constrained by locations of aftershock seismicity based on the International Maule Aftershock Data Set. The maximum slip on the main fault is about 3 m and, consistent with field results, the onshore slip is close to zero near the surface. Satellite radar data also reveal that significant aseismic afterslip occurred following the two earthquakes. Coulomb stress modelling indicates that the faults were positively stressed by up to 40 bars as a result of slip on the subduction interface in the preceding megathrust event; in other words, the Pichilemu earthquakes should be considered aftershocks of the Maule earthquake. The occurrence of these extensional events suggests that regional interseismic compressive stresses are small. Several recent large shallow crustal earthquakes in the overriding plate following the 2011 Mw 9.0 Tohoku-Oki earthquake in Japan may be an analogue for the triggering process at Pichilemu.

The Kern Canyon fault represents a major tectonic and physiographic boundary in the southern Sierra Nevada of east-central California. Previous investigations of the Kern Canyon fault underscore its importance as a Late Cretaceous and Neogene shear zone in the tectonic development of the southern Sierra Nevada. Study of the late Quaternary history of activity, however, has been confounded by the remote nature of the Kern Canyon fault and deep along-strike exhumation within the northern Kern River drainage, driven by focused fluvial and glacial erosion. Recent acquisition of airborne lidar (light detection and ranging) topography along the ∼140 km length of the Kern Canyon fault provides a comprehensive view of the active surface trace. High-resolution, lidar-derived digital elevation models (DEMs) for the northern Kern Canyon fault enable identification of previously unrecognized offsets of late Quaternary moraines near Soda Spring (36.345°N, 118.408°W). Predominately north-striking fault scarps developed on the Soda Spring moraines display west-side-up displacement and lack a significant sense of strike-slip separation, consistent with detailed mapping and trenching along the entire Kern Canyon fault. Scarp-normal topographic profiling derived from the lidar DEMs suggests normal displacement of at least 2.8 +0.6/–0.5 m of the Tioga terminal moraine crest. Cosmogenic 10Be exposure dating of Tioga moraine boulders yields a tight age cluster centered around 18.1 ± 0.5 ka ( n = 6), indicating a minimum normal-sense fault slip rate of ∼0.1–0.2 mm/yr over this period. Taken together, these results provide the first clear documentation of late Quaternary activity on the Kern Canyon fault and highlight its role in accommodating internal deformation of the southern Sierra Nevada.

Paleoseismic trenching within Fort Ross State Historic Park provides data on the late Holocene rupture history of the North Coast segment of the northern San Andreas fault. The 1906 earthquake ruptured through the Fort Ross Orchard site, which is characterized by a narrow shutter ridge and associated linear trough containing latest Holocene sediments. Trenches across the northeast-facing fault scarp exposed sediments interpreted as scarp-derived colluvium and possible fissure-fill deposits, and tentative upward fault truncations that provide evidence of three possible surface ruptures prior to 1906. Coarse-grained scarp-derived colluvial sediments were deposited after individual surface-rupturing earthquakes that predate the 1906 rupture. Radiocarbon analyses of 31 detrital radiocarbon samples collected from the colluvial deposits constrain the timing of earthquakes over the past approximately 1000 years. Based on stratigraphic ordering and a statistical comparison of radiocarbon dates using the OxCal program, we estimate (at a 95% confidence level) that three pre-1906 surface ruptures at the Orchard site occurred at a.d. 1660–1812, a.d. 1220–1380, and a.d. 1040–1190. Previous trenches at the nearby Fort Ross Archae Camp site are consistent with these dates and further suggest the occurrence of an earlier event between a.d. 555 and 950. Collectively, the Fort Ross Orchard and Archae Camp sites suggest pre-1906 ruptures at a.d. 1660–1812, a.d. 1220–1380, a.d. 1040–1190, and a.d. 555–950. The time windows for these ruptures are consistent with results from other sites on the North Coast segment of the San Andreas fault. However, additional information on the late Holocene history of rupture events on adjacent fault segments is needed to evaluate whether the long-term behavior of the San Andreas fault involves a mix of large, 1906-type ruptures and shorter, segment-specific ruptures.

Many important insights are embedded in the detailed observations of surface rupture of the 1906 San Francisco earthquake, during which surface faulting interacted with pipelines, earth embankments, and buildings. Lessons gleaned from the 1906 rupture, combined with parallel and new insights from recent earthquakes, illustrate how various geologic conditions alter the surface expression of faulting and how surface fault rupture interacts with engineered systems. Geologic and engineering procedures can be employed to evaluate the hazards associated with surface faulting and to develop sound designs. Illustrative examples are used to demonstrate how the hazards associated with surface fault rupture can be addressed. Effective design measures include constructing earth fills to partially absorb underlying ground movements; isolating foundations from the underlying ground movements; and designing strong, ductile foundations that can accommodate some deformation without compromising the functionality of the structure.

The Niigata Ken Chuetsu earthquake triggered a vast number of landslides in the epicentral region. Landslide concentrations were among the highest ever measured after an earthquake, and most of the triggered landslides were relatively shallow failures parallel to the steep slope faces. The dense concentration of landslides can be attributed to steep local topography in relatively weak geologic units, adverse hydrologic conditions caused by significant antecedent rainfall, and very strong shaking. Many of the landslides could be discerned from high-resolution satellite imagery acquired immediately after the earthquake.

The Niigata Ken Chuetsu earthquake induced significant geotechnical and geologic failures throughout the affected region. The most prevalent geotechnical observations from this earthquake are related to ground failure, including landslides in natural ground, failures of highway embankments and residential earth fills, and limited liquefaction in alluvial deposits. The absence of considerable levee deformations and surface faulting was noted. This paper documents the geotechnical aspects of the Niigata Ken Chuetsu earthquake as related to earth structures, liquefaction, and surface faulting; landslides are discussed in an accompanying paper.

The New Madrid North and Reelfoot Faults are believed to have ruptured during large-magnitude earthquakes on 23 January and 7 February 1812, respectively, based on the regional distribution of liquefaction, contemporary New Madrid seismic zone microseismicity, and historical accounts of earthquake-related damage. Although the location of the Reelfoot Fault generally is well constrained between the Kentucky Bend of the Mississippi River in Kentucky and the southeastern margin of the Mississippi Valley in Tennessee, the northern extent of the fault remains enigmatic in southeastern Missouri. This is equally true of the New Madrid North Fault, which has a postulated location based primarily on contemporary microseismicity and rupture scenario models of the 1811-1812 earthquake sequence. In this paper, we synthesize existing unpublished and published data with recently acquired subsurface and geomorphic information to clarify the locations of the Reelfoot and New Madrid North Faults in southeastern Missouri. On the basis of this data synthesis, we interpret that the Reelfoot Fault trends northwest across the Kentucky Bend of the Mississippi River as a northwest-facing scarp coincident with Des Cyprie Slough near New Madrid, Missouri, and anomalous elevated topography on southern Sikeston Ridge northwest of New Madrid. Furthermore, Quaternary faulting and folding imaged from seismic-reflection profiles across Des Cyprie Slough coincide with bedrock structural lineaments, a northeast-trending band of contemporary microseismicity, and a distinct northwest-trending post-Tertiary change in alluvial thickness. We trace the Reelfoot Fault as much as several kilometers northwest of the Mississippi River, where it either dies out or steps north-northeast to merge with the New Madrid North Fault. The New Madrid North Fault appears to be expressed geomorphically as left-stepping, en echelon northeast-trending fractures preserved in Pleistocene glacial outwash material comprising Sikeston Ridge. The fractures coincide with Quaternary faults and folds, as well as deeper Cretaceous and Paleozoic faults and flexures, imaged in geophysical profiles. In summary, the surface locations of the Reelfoot and New Madrid North Faults directly west-northwest of New Madrid, Missouri are constrained by geomorphic, geologic, geophysical, and historical seismological data sets and reflect transfer of strain from the northeast-verging Reelfoot reverse fault to the northeast-striking, dextral New Madrid North Fault.

The Chi-Chi earthquake provides dramatic evidence of the damaging effects of surface ground deformation to buildings, lifelines, and other facilities. Much of the building damage is associated with surface faulting and folding along the Chelungpu thrust fault. Our detailed surveying at representative sites along the fault shows that the rupture commonly is a relatively simple 1- to 4-m-high scarp with minor hanging-wall deformation and localized (but severe) uplift, folding, and graben formation along the scarp crest. For individual scarps, the width of deformation is about 10 to 20 times the net vertical displacement. Distributed secondary faulting and folding on the hanging wall occurred as much as 350 m from the primary fault. Near the northern end of the rupture, growth of a pre-existing 1-km-wide late Quaternary anticline produced severe ground rupture along multiple thrusts and backthrusts but only minor tilting between fault strands. The pattern of building damage coincides with the pattern of geologic deformation, with severe damage along large fault scarps and lesser but still significant damage attributable to distributed secondary surface deformation on the hanging wall. Rupture-related building damage on the footwall occurred next to the prerupture fault trace, where the hanging wall bulldozed onto the footwall. The width of this damage zone is related to the local horizontal shortening along the fault and generally is less than 10 m. Building zonation along reverse faults should account for this pattern of surface deformation. In addition, buildings with massive foundations locally influenced the style and location of near-surface deformation, producing variations in fault strike or accentuated secondary deformation on the hanging wall. Manuscript received 15 January 2001.

A general method for nondestructive mapping of three-dimensional surfaces, particularly useful in cases where the surface is composed of a large array of identical depressions, is presented. The sample is first marked with a uniform flux of particles, which then act as isotropic sources of some detectable radiation. By measuring the emitted radiation from several directions, it is possible to reconstruct the surface using a parametrization coupled with a least squares fit procedure. As an example, we report on the experimental implementation of the algorithm to arrays of micron-scale inverted pyramids etched in GaAs substrates, using a particular sequence of alpha emitting atoms.

The dextral strike-slip New Madrid North Fault (NMNF) is interpreted by others to have ruptured during the 23 January 1812, M 7.8 earthquake. Although widespread liquefaction was associated with this earthquake and is evident today, the NMNF's surface trace remains enigmatic. Our surficial geologic mapping in southeast Missouri identifies two prominent northeast-trending, 3- to 3.5-km-long lineaments (North and South Farrenburg lineaments) traversing Sikeston Ridge. The lineaments are expressed by apparent right-laterally deflected paleodrainages, scarplets, swales, linear troughs, and tonal contrasts in late Pleistocene deposits. Northeast-trending contemporary microseismicity and previously inferred NMNF locations align partly with the lineaments. Borehole data show a linear change in thickness (5 m) of post-Tertiary alluvium trending N30°–35°E for 35 km across both Sikeston Ridge and a Holocene fluvial surface east of the ridge. This thickness change coincides with microseismicity, apparent right-laterally separated isopachs, aeromagnetic anomalies, and the North and South Farrenburg lineaments. Our interpretation of S -wave seismic-reflection profiles acquired across the North Farrenburg lineament also suggests warped and faulted Quaternary deposits. Four trenches excavated across the North Farrenburg lineament exposed late Pleistocene interbedded clay, silt, and sand. The trenches also exposed linear liquefaction vents that trend N20°E to N55°E, near-vertical faults striking N30°E and N42°E, and a possibly warped Pleistocene paleochannel. Vented sand extends upward nearly to the ground surface, suggesting that the vents were produced during the 1811–1812 earthquakes. Oriented sediment samples collected from the fault zones and vents and analyzed with an SEM identified fractured sand grains across the faults, suggesting that the displacement exposed in the trenches may be of primary tectonic origin. Similar sediment samples collected from undeformed sand and from the sand vents show no evidence of grain fracturing and reduction. We hypothesize that the geomorphic, geologic, seismic reflection, trench, and microtextural data strongly suggest that the North Farrenburg lineament, as well as the South Farrenburg lineament, may be the surface expression of an underlying tectonic fault.

Paleoseismic investigation of the Northridge Hills fault in the northern San Fernando Valley, California, helps assess the timing and style of near-surface late Quaternary deformation in the epicentral area of the 1994 Northridge earthquake. The Northridge Hills fault, a 15-km-long, north-dipping reverse fault, exhibits geomorphic evidence of late Quaternary surface deformation, including topographic scarps across late Quaternary fluvial terraces and aligned alluvial-fan apices on the footwall block. We excavated one 40-m-long trench and six test pits, and drilled nine boreholes across a 2-m-high scarp developed on a probable Holocene fluvial terrace adjacent to Aliso Canyon Wash. A continuous clayey gravel identified in the trench, test pits, and boreholes defines a south-facing monocline with 6 ± 1 m of vertical separation across the Northridge Hills fault. Based on pedochronology, the clayey gravel ranges in age from 6 to 30 ka. The borehole data also suggest that an unconformity developed on the Plio-Pleistocene Saugus Formation is warped into a monocline that has 13 ± 2 m of vertical separation across the fault. These preliminary data yield a dip-slip rate of 1.0 ± 0.7 mm/yr for the Northridge Hills fault. The absence of distinct scarp-derived colluvium in trench exposures at the base of the scarp and secondary brittle fracturing or faulting suggests that the monocline is related to folding during small, incremental uplifts rather than large uplifts that generate distinct scarp relief. We postulate that such uplift could be produced via moderate-magnitude earthquakes ( M W 6¼) on the Northridge Hills fault, or secondary deformation induced by earthquakes on other faults. For instance, evidence of surface uplift near the trench site during or following the 1994 earthquake suggests that all or part of the observed deformation is a result of secondary slip on the Northridge Hills fault produced by movement on the underlying Northridge blind reverse fault or other nearby large structures. Based on our geologic investigations, the distribution of aftershocks following the 1994 earthquake, and pre- and post-1994 leveling and geodetic surveys, we interpret that the Northridge Hills fault underwent triggered slip during the 1994 earthquake.

Measurements of nuclear stimulated desorption (NSD) of 107 Cd from a (111) nickel single crystal surface covered with a fraction of a monolayer of palladium were performed. The total desorption probability and the polar angular distribution were determined. An anisotropic distribution with a minimum in the upward direction was found. This distribution is compared with molecular dynamics calculations and is shown to be consistent with desorption from step sites. It is also qualitatively consistent with independent results on similar systems obtained by the perturbed angular correlation method using 111 m Cd. The total desorption probability agrees with the predicted value. Future work required to turn NSD into a useful analytic tool is discussed.

Paleoseismic trenching was performed to assess the slip rate and earthquake history of the northern segment of the Calaveras fault at a site along Welch Creek in the eastern San Francisco Bay area, California. At Welch Creek, the northern Calaveras fault crosses a series of fluvial terraces and displaces the intervening terrace risers. We derive a late Holocene slip rate using two independent methods: (1) by measuring the offset of the back-edge (i.e., terrace angle) of one of the offset terraces and (2) by using isopach contours to measure the offset of a debris flow unit within the terrace sediments. The terrace back-edge is offset 39 ± 1 m and is between 5 and 13 ka old. The debris flow deposit is offset 27 ± 1 m; the deposit age is estimated to be between 4840 and 5325 cal yr B.P. These findings suggest a late Holocene slip rate of 6 ± 1 mm/yr for the northern Calaveras fault. We recognize as many as seven surface-rupturing earthquakes at Welch Creek, although the amount of terrace back-edge displacement suggests that several more events must have occurred that are not discernable in the stratigraphic or structural record. Based on the maximum amount of time between age-constrained paleoearthquakes that are preserved in the record at Welch Creek, we derive an estimate of the maximum recurrence interval of between 1375 and 3425 yr. Using the assumption that additional events are required to account for the 39 ± 1 m of back-edge offset, we derive a recurrence estimate of between 125 and 685 yr.

Molecular dynamics calculations of low energy Nuclear Stimulated Desorption (NSD) of 107 Cd from a palladium substrate are presented. The characteristics of the desorption probability are shown to be related both to the site occupied by the 107 Cd and to the adsorbate–substrate interaction. The quantitative implications of the theoretical calculations to a specific experimental scenario are discussed, based on preliminary measurements of 107 Cd desorption from palladium.

The α-particle energy loss method (AEL) has been implemented in situ to monitor film thickness and composition during growth of GaAs, InP and LaF 3 based materials by molecular beam epitaxy (MBE). In the AEL method, a 228 Th source is used to recoil implant a 5 mm diameter region of the surface of the wafers with the α-emitter daughter isotope 224 Ra prior to growth. The implanted nuclei decay with a half life of 3.7 days through a sequence of daughters which emit alpha particles at different energies. Deposition on the surface causes the emission lines to be shifted to lower energies due to energy loss in the film. For substrates marked with a low activity (∼ 30 kBq; similar to activity of smoke detectors) we are able to measure film thickness with ± 6 nm uncertainty and growth rate with ± 0.01 nm/s uncertainty in real time. By measuring the relative growth rates of the different materials, AEL also allows us to infer the composition of a ternary laver film as well as the sticking coefficients rates directly at different growth temperatures.

Backreflection of the residual pump power into the cavity, and optimization of the fiber length, may significantly improve the efficiency of a strongly pumped fiber laser. A rate equation model is introduced and studied. Examples for Yb/sup 3+/-doped fiber lasers, with DBR mirrors at either end, show that employing such a geometry results in higher efficiency with shorter optimal fiber length. Approximate analytical and quasi-analytical expressions are shown to be in excellent agreement with the exact numerical solution of the rate equations.

Parallel molecular dynamics calculations of nuclear-stimulated desorption are carried out for a palladium crystal containing radioactive atoms. The characteristics of the desorption probability and their dependence on different interaction parameters are presented. The implications of the results to an experimental scenario which may enable better understanding and modelling of adsorbate-substrate interaction are discussed.

The temperature dependence of the diffusion of lead in GaAs is determined by measuring the modification to the energy spectrum of emitted alpha particles from the decay chain of implanted 212Pb atoms. Diffusion rates are measured for temperatures up to 900 °C. Higher rates are observed for the diffusion in silicon-doped GaAs than in semi-insulating GaAs. An upper limit for the diffusion of radium in GaAs is similarly obtained from the decay of the 224Ra isotope. Implications for the use of implanted alpha sources for thickness monitoring during epitaxial film growth by the alpha-particle energy loss method are discussed.

Strongly pumped fiber lasers are analyzed, based on a rate equation model. Examples include Nd/sup 3+/-doped and Yb/sup 3+/-doped fiber lasers, with distributed Bragg reflector mirrors at either end. Approximate analytical and quasi-analytical expressions are shown to be in excellent agreement with the exact numerical solution of the rate equations, and both agree well with recently published experimental data.

The α-particle energy loss method has been implemented in situ to monitor film thickness during growth by molecular beam epitaxy. For InP and GaAs substrates dosed with 500–1500 Bq of α-particle emitters, we have been able to measure thickness in situ of deposited GaAs and InP, to an accuracy of 6 nm in 180 s of counting time. The corresponding growth rate accuracy for growth rates on the order of 0.3 nm/s was ±0.01 nm/s. The accuracy and counting time improvements expected with the use of a stronger marking source are also discussed.

A method for determining both the thickness and the average stoichiometry of thin films is presented. The method is based on implanting radioactive -sources in the substrate prior to layer growth and measuring the energy loss of the -particles as they traverse the layer. Information about the stoichiometry is obtained through the comparison of the energy loss of -particles of different initial energies. Experimental examples for the utilization of this method are presented, in which Sb was grown on Si substrates, GaAs, InAs and AlAs on GaAs and YBCO on YSZ. The experimental precision which can be expected using the method is discussed, together with specific scenarios in which it could be advantageously applied.

Surface fault rupture resulted from the 11 April 2011 Mw 6.6 Hamadoori aftershock of the 2011 Mw 9.0 Tōhoku earthquake. This paper documents the surface rupture pattern and its interaction with a school gymnasium and pool. Locally along the rupture, surface offset was distinct, but at the school site, ground deformation was distributed across a wide zone. LIDAR-derived data show that the structures were tilted and warped as a result of surface rupture. Numerical analysis shows that semi-consolidated Tertiary sedimentary rocks were ductile and that prior fault ruptures may have not developed fully within the surficial materials. This is analogous to surface rupture interactions with engineered fills that exhibit ductile responses.

The northern Calaveras fault traverses a heavily populated area in the eastern San Francisco Bay region and has not had a large earthquake in more than 130 years. To obtain data on the number, timing, and recurrence of large paleoearthquakes, we conducted paleoseismologic investigations at Leyden Creek, which crosses the fault in the rugged southern East Bay Hills. The site is characterized by a prominent west facing scarp and fivc fluvial terraces on the western (upstream) side of the fault. On the eastern (downstream) side of the fault, the creek flows through a narrow bedrock canyon that constricts the modern valley and has constrained the location of a late Pleistocene palcovalley. The margin of a buried bedrock valley west of the fault trends nearly perpendicular to the fault and is offset 54 (+18, -14) m in a right-lateral sense from the narrow bedrock canyon. Based on radiocarbon ages for alluvial sediments predating and postdating this paleovalley margin, we estimate an age of 11.5 (+3, -1) ka for the valley margin and a Holocene slip rate of 5 ± 2 mm/yr for the fault at Leyden Creek. Slickensides exposed in multiple trenches across the fault show that the most recent movement was predominantly lateral with a minor component of down-to-the-west slip. Multiple displaced scarp-derived colluvial deposits are interpreted as results of five or six surface ruptures within the past 2500 years. Twenty-one radiocarbon samples from scarp-derived colluvium and interfingered alluvial deposits suggest an average interval between surface rupture carthquakes of 250 to 850 years.

The Reelfoot fault is an east vergent, reverse fault underlying the Lake County uplift, a low-amplitude, late Holocene anticline bordered on the east by the 32-km-long Reelfoot scarp. Fluvial deposits across the scarp define an 8-m-high, east facing monocline. Most near-surface deformation along the scarp is accommodated via folding rather than faulting. We interpret the scarp as a fault-propagation fold developed over a wcst dipping reverse fault interpreted from shallow seismic reflection data. Trench exposurcs provide evidence for three episodes of deformation along the Reelfoot fault within thc past approximately 2400 years, between A.D. 780 and 1000, between A.D. 1260 and 1650, and during A.D. 1812. Our best estimate of the average recurrence interval for deformation along the scarp is 400-500 years. Each episode of deformation had a slightly different style. The third most recent event produced a small graben a few tens of centimeters deep in the hanging wall of the reverse fault. The second most recent earthquake produced about 1.3 m of throw in the graben, as well as folding along the updip projection of the reverse fault and development of the scarp. Thesc relations suggest that graben development increased through time concomitant with growth of the monocline or that the events are of different magnitude. The 1811-1812 episode of deformation produced abundant liquefaction, prominent folding of fluvial strata along the scarp, and minor faulting in the graben.

A method of optimizing molecular dynamics calculations is presented. The method employs multiple time steps across the computational crystal both for the force evaluation and the neighbor list updating. The time step for each individual atom is chosen according to general criteria which reproduce overall accuracy while saving CPU time. A detailed application is presented to demonstrate the reduction in computation time and the reproducibility of the results.

The Reelfoot scarp in northwestern Tennessee is the surface expression of an east-verging fault propagation fold that overlies a southwest-dipping reverse fault. This fault is responsible for much of the current New Madrid seismicity and was probably the origin of the February 7, 1812, M 8.0 earthquake. Tectonic scarps in the Kentucky bend of the Mississippi River and at New Madrid, Missouri, appear to be a northwestern continuation of the Reelfoot scarp. Cores collected across the scarp in Kentucky where the topographic relief is 2.2 m reveal that the structural relief on a distinct subsurface fluvial sand bed is 4 m. One kilometer to the north the topographic relief is 3 m and structural relief is 4 m. Similarly, the scarp at New Madrid, Missouri, has 2 m of topographic and structural relief. These core data are compatible with trench observations to the south where the fold structure is reflected...

A sequence of radioactive decays can be used to implant alpha-emitting sources in substrates for thickness measurements of films grown on them. Starting with 228Th, both direct recoil implantation of 224Ra and a two-stage recoil implantation of 212Pb were performed. The thickness of germanium layers grown on gallium arsenide was determined by measuring the energy loss of the alpha particles traversing them. The results were found to be consistent with those obtained by other methods. The special advantages of the present procedure are discussed.

A series of measurements of nuclear stimulated desorption was performed for 103Ru, using thin ruthenium films irradiated by thermal neutrons. The magnitude, time dependence and electric charge state of the outgoing 103Rh flux was investigated. The utilization of monoenergetic electrons accompanying the 103Rh decay for thin film thickness measurement is considered.

This reply addresses the three main comments by Shlemon et al. (2001), namely that our article (1) provided inadequate reference to a large body of earlier work, (2) yielded a conclusion that had already been made, and (3) estimated a range in slip-rate uncertainty that is too large. We address these three issues individually. First, we acknowledge that the Northridge Hills fault was identified many years ago and that it was previously interpreted as a probable active fault. However, Shlemon et al. (2001) implied that Baldwin et al. (2000) failed to acknowledge the earlier work performed by others (Barnhart and Slosson, 1973; Saul, 1975; and Johnson et al., 1996). They also suggest that earlier geomorphic and geologic observations by Barnhart, Slosson, and Saul are sufficient to define the seismogenic potential of the Northridge Hills fault. We disagree. As stated in our article, the Northridge Park trench site “... was selected on the basis of detailed geologic and geomorphic mapping of surficial deposits in the northern San Fernando Valley (Hitchcock and Kelson, 1996; Wills and Hitchcock, 1999),” (p. 631) in addition to the earlier work performed by others (e.g., Barnhart and Slosson, 1973; Smith, 1977; Saul, 1979; Dibblee, 1992). We also referenced Johnson et al. (1996) throughout the manuscript. The detailed 1:24,000-scale mapping of surficial deposits summarized by Hitchcock and Kelson (1996) and Wills and Hitchcock (1999) has recently been published by the California Division of Mines and Geology as Map Sheet 50 (1:48,000-scale) (Hitchcock and Wills, 2000). Second, we acknowledge that the Northridge Hills fault was interpreted as a possible active fault (Barnhart and Slosson, 1973), but also note Barnhart and Slosson (1973) state “Proper credence to the …

A series of measurements of nuclear stimulated desorption was performed for compounds containing the isotopes 47Ca and 99Mo. A persistent charged component was observed in the desorbed flux of 47Sc resulting from the decay of 47Ca. A transient charged component in the flux of 99mTc was detected for some chemical forms of the 99Mo compound.

Stratigraphic and structural relations exposed in a 90-m-long trench across the Reelfoot scarp in the central New Madrid Seismic Zone (NMSZ) provide data to assess the style and timing of late Holocene tectonic surficial deformation in the central NMSZ. Near-surface deposits exposed in the trench include natural levee, overbank, colluvial, and liquefaction-related deposits. The levee deposits consist of fine-grained, cross-bedded sands and silty sands and are overlain by clayey overbank and scarp-derived colluvial deposits. Liquefaction-related features include sand dikes and sills that intrude into the levee and overbank deposits, and a possible older extrusive sand deposit. Charcoal and archaeological artifacts from a deposit inset into and overlying the levee deposits suggest that the levee deposits are older than about A.D. 800 to 900. Charcoal from the overbank deposits yielded an age estimate of cal. A.D. 1310 ± 90; charcoal from the overlying colluvial deposits yielded an age estimate of cal. A.D. 1540 ± 90. Distinct marker beds within the levee deposits define a broad monocline that parallels the ground surface and exhibits more than 5 m of down-to-the-east vertical separation. This fold consists, in part, of four smaller-scale flexures each having amplitudes of about 1 m. Associated with these flexures are numerous west-dipping normal faults that have a total net vertical separation of about 0.4 m in a down-to-the-west sense, which is opposite in sense to that exhibited by the scarp and the silty marker beds. We interpret that these faults are related to extension in the crest of the monocline, and that the monocline represents deformation above a west-dipping reverse fault that reaches or approaches the ground surface east of the trench and the base of the scarp. At the trench site, this interpretation places the surface projection of the fault near the western margin of Reelfoot Lake. Stratigraphic relations exposed in the trench and several shallow boreholes permit identification of at least one and possibly three late Holocene earthquakes. Stratigraphic relations and age-estimates best support the interpretation that the unweathered liquefaction related features exposed in the trench are a result of the 1811–12 earthquakes, and that the scarp-derived colluvial deposits are a result of a prior event. Radiocarbon analyses show that this penultimate event occurred between about A.D. 1310 and A.D. 1540. Stratigraphic evidence of a third event prior to about A.D. 900 is present but equivocal. Given that the most-recent event occurred in A.D. 1812, we estimate that the time between the two most-recent earthquakes large enough to produce liquefaction and/or surface deformation was about 200 to 600 years.

Molecular dynamics calculations of nuclear stimulated desorption are carried out for a palladium crystal containing radioactive palladium atoms. The total desorption probability from various sites are computed, as well as the angular distribution of the desorbing atoms. The implications of the results to different experimental scenarios are discussed.

The α-particle energy loss method (AEL) has been implemented in situ to monitor film thickness during growth by molecular beam epitaxy. For InP and GaAs substrates recoil implanted with α-particle emitters, we have been able to measure thickness and composition of deposited GaAs, AlGaAs and InGaAs in real time. The AEL method yields in situ real time results comparable in accuracy to those obtained by ex situ scanning electron microscope and high-resolution x-ray diffraction measurements.

The San Andreas, Hayward, and Calaveras faults are major active faults that traverse the San Francisco Bay area in northern California, and may produce surface rupture during large earthquakes. We assessed the entire Pacific Gas & Electric Company natural gas transmission system in northern California, and identified several locations where primary pipelines cross these faults. The goal of this effort was to develop reasonable measures for mitigating fault-rupture hazards during the occurrence of various earthquake scenarios. Because fault creep (e.g., slow, progressive movement in the absence of large earthquakes) occurs at the pipeline fault crossings, we developed an innovative approach that accounts for the reduction in expected surface displacement, as a result of fault creep, during a large earthquake. In addition, we used recently developed data on the distribution of displacement across fault zones to provide likely scenarios of the seismic demand on each pipeline. Our overall approach involves (1) identifying primary, high-hazard fault crossings throughout the pipeline system, (2) delineating the location, width, and orientation of the active fault zone at specific fault-crossing sites, (3) characterizing the likely amount, direction, and distribution of expected surface fault displacement at these sites, (4) evaluating geotechnical soil conditions at the fault crossings, (5) modeling pipeline response, and (6) developing mitigation measures. At specific fault crossings, we documented fault locations, widths, and orientations on the basis of detailed field mapping and exploratory trenching. We estimated fault displacements based on expected earthquake magnitude, and then adjusted these values to account for the effects of fault creep at the ground surface. Fault creep decreases the amount of expected surface fault rupture, such that sites having high creep rates are expected to experience proportionally less surface displacement during a large earthquake. Lastly, we modeled the expected amount of surface offset to reflect the distribution of offset across the fault zone, based on data from historical surface ruptures throughout the world. Where specific fault crossings contain a single primary fault strand, we estimated that 85% of the total surface offset occurs on the main fault and the remainder occurs as secondary deformation. At sites where the pipeline crosses multiple active fault strands in a broad zone, we consider complex rupture distributions. Using this approach yields realistic, appropriately conservative estimates of surface displacement for assessing seismic demands on the pipelines.Copyright © 2004 by ASME

This paper describes the development of a unique pipeline fault crossing design upgrade for a 22-inch (559 mm) diameter Pacific Gas & Electric Company (PG&E) gas transmission line where it crosses the Calaveras fault near Sunol, California. The new design is capable of withstanding significant levels of horizontal fault offset while minimizing the deformation demands experienced by the pipeline. This unique design concept is applicable to fault crossings with well defined fault locations and highly localized fault offset profiles (e.g., for this fault, 85% of the offset is expected to occur within ±5 feet (±1.5 m) from the center of the fault trace, which was precisely located by field trenching studies). Relative to the original fault crossing design, the new design provides a more favorable “local” fault crossing angle “β” (β = 73° for the original design vs. β = 95° for the new design). The angle change is accomplished by installing an offset section of the pipeline adjacent to the fault such that the fault crosses the pipeline in the middle of a tangent section in the nearest offsetting leg. The four bends used to fabricate the offset section are cold bends with an average radius of 76.4 feet (23.3 m). The entire mitigated section of the pipeline is buried in a select sand trench. For this design configuration, right lateral fault motion results in (a) a “closing” action within the two adjacent cold bends located on either side of the fault and (b) a net tension force in the pipe (due to the obtuse β value) centered on the tangent section of the offsetting leg containing the fault crossing. The net tension force in the offsetting leg results in an “opening” action within the two adjacent cold bends on either side of the fault. By adjusting the local fault crossing angle β, the “bend opening” action that results from pipe extension across the fault can be made to nearly offset the “bend closing” action induced by the transverse component of the fault offset. The use of a select sand backfill in the retrofit section allows the bends to engage the soil with relatively low transverse and longitudinal resistance thereby enhancing the overall flexibility/compliance of the fault crossing design. Implementation of this unique design concept at the Calaveras fault crossing increased the amount of fault offset required to damage the pipeline from about 7 inches (18 cm) for the “as-built” design to well over 90 inches (2.3 m) for the retrofit.