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At least 1,153 records · Page 64Linked to original sources

USGS2026

Hydrologic investigation of water level fluctuations at Moreau Lake, Moreau Lake State Park, town of Moreau, New York

The causes of water level fluctuations at Moreau Lake, within Moreau Lake State Park in the town of Moreau, New York, were investigated from 2016 to 2021 after lake water levels dropped between 2015 and 2016, raising concerns about the loss of a shallow swimming area at the park beach. Annual variation in precipitation records from the area did not account for the lake water level decline. Two possible causes for the low lake water levels were investigated: the increase in groundwater withdrawals from new residential development since about 2000 and seasonal changes (nongrowing and growing seasons) in precipitation. Investigation of the potential effects of nearby groundwater withdrawals required the compilation and collection of well-log data, seismic surveys, and measurements of lake and groundwater levels, field chemical parameters, and water isotopes to define the hydrogeologic system and to estimate water use. The net result of this work was the determination that Moreau Lake is a “flow though” lake with no surface water outlet; groundwater enters the lake on the upgradient side and exits through the downgradient side, however, groundwater does not flow southward from the lake toward nearby groundwater withdrawals from the semiconfined aquifer, and thus groundwater withdrawals were unlikely to have an effect on lake water levels. Investigation of the historic precipitation records during nongrowing (November through April) and growing (May through October) indicated that (1) nongrowing season precipitation from 2011–12 to 2015–16 was more deficient than any similar period during the past 78 years and (2) since about 2000, nongrowing seasons have been drier overall and growing seasons have been considerably wetter. Initiation of lake water level monitoring in 2016 provided an opportunity to compare seasonal precipitation with seasonal lake water level changes. Nongrowing season lake water levels are very sensitive to precipitation, such that high precipitation (40 percent above the seasonal median) resulted in a 5-foot rise in lake water level. In contrast, the growing season lake water levels are sensitive to dry conditions; for example, deficient rainfall (about 6 percent below the seasonal median) resulted in a decline of lake water levels of about 3.5 feet. However, lake water levels are insensitive to high growing season rainfall inputs (about 10 to 47 percent above the seasonal median); lake water levels consistently declined about by 0.8 feet above this range of seasonal excessive precipitation.

New York↗

USGS2015

Southern San Andreas Fault seismicity is consistent with the Gutenberg-Richter magnitude-frequency distribution

The magnitudes of any collection of earthquakes nucleating in a region are generally observed to follow the Gutenberg-Richter (G-R) distribution. On some major faults, however, paleoseismic rates are higher than a G-R extrapolation from the modern rate of small earthquakes would predict. This, along with other observations, led to formulation of the characteristic earthquake hypothesis, which holds that the rate of small to moderate earthquakes is permanently low on large faults relative to the large-earthquake rate (Wesnousky et al., 1983; Schwartz and Coppersmith, 1984). We examine the rate difference between recent small to moderate earthquakes on the southern San Andreas fault (SSAF) and the paleoseismic record, hypothesizing that the discrepancy can be explained as a rate change in time rather than a deviation from G-R statistics. We find that with reasonable assumptions, the rate changes necessary to bring the small and large earthquake rates into alignment agree with the size of rate changes seen in epidemic-type aftershock sequence (ETAS) modeling, where aftershock triggering of large earthquakes drives strong fluctuations in the seismicity rates for earthquakes of all magnitudes. The necessary rate changes are also comparable to rate changes observed for other faults worldwide. These results are consistent with paleoseismic observations of temporally clustered bursts of large earthquakes on the SSAF and the absence of M greater than or equal to 7 earthquakes on the SSAF since 1857.

California↗

USGS1978

Preliminary catalog of earthquakes in northern Imperial Valley, California, October 1977-December 1977

The northern section of the Imperial Valley region in southern California is an area of known geothermal resources and an area of high seismicity. To study in detail the relationship between geothermal areas and earthquakes, the U.S. Geological Survey has been monitoring seismicity in the Imperial Valley with a 16-station network since 1973. Six new stations were added to the network in November 1976. This catalog contains a description of the network and a list of preliminary data on earthquakes recorded by the network from October 1977 through December 1977.

California↗

USGS1978

Preliminary catalog of earthquakes in northern Imperial Valley, California, January 1, 1977 to March 31, 1977

The northern section of the Imperial Valley region in Southern California is an area of known geothermal resources and an area of high seismicity. To study in detail the relationship between geothermal areas and earthquakes, the U.S. Geological Survey has been monitoring seismicity in the Imperial Valley with a sixteen station network since 1973. Six new stations were added to the network in November 1976. This catalog contains a description of the network and a list of preliminary data on earthquakes recorded by the network from January 1977 through March 1977.

California↗

USGS2011

Revelations from ambient shaking data of a recently instrumented unique building at MIT campus

A state-of-the-art seismic monitoring system comprising 36 accelerometers and a data-logger with real-time capability was recently installed at Building 54 on the campus of the Massachusetts Institute of Technology [MIT], Cambridge, Massachusetts. The system is designed to record translational, torsional and rocking motions, and to facilitate computation of drift between select pairs of stories. The cast-in-place, reinforced concrete building is rectangular in plan but has vertical irregularities. Heavy equipment is installed asymmetrically on the roof. Spectral analyses and system identification performed on one set of low-amplitude ambient data reveal distinct fundamental translational frequencies in the structural NS and EW directions [0.75 and 0.67Hz, respectively], a torsional frequency of 1.49 Hz, a rocking frequency of 0.75 Hz, and very low damping. Such results from low-amplitude data serve as baseline against which to compare the behavior and performance of the building during stronger shaking caused by future earthquakes in the region.

Massachusetts↗

USGS2009

Seismic monitoring to assess performance of structures in near-real time: Recent progress

Earlier papers have described how observed data from classical accelerometers deployed in structures or from differential GPS with high sampling ratios deployed at roofs of tall buildings can be configured to establish seismic health monitoring of structures. In these configurations, drift ratios are the main parametric indicator of damage condition of a structure or component of a structure. Real-time measurement of displacements are acquired either by double integration of accelerometer time-series data, or by directly using GPS. Recorded sensor data is then related to the performance level of a building. Performance-based design method stipulates that for a building the amplitude of relative displacement of the roof of a building (with respect to its base) indicates its performance. Usually, drift ratio is computed using relative displacement between two consecutive floors. When accelerometers are used, determination of displacement is possible by strategically deploying them at a select number of pairs of consecutive floors. For these determinations, software is used to compute displacements and drift ratios in real-time by double integration of accelerometer data. However, GPS-measured relative displacements are limited to being acquired only at the roof with respect to its reference base. Thus, computed drift ratio is the average drift ratio for the whole building. Until recently, the validity of measurements using GPS was limited to long-period structures (T>1 s) because GPS systems readily available were limited to 10–20 samples per seconds (sps) capability. However, presently, up to 50 sps differential GPS systems are available on the market and have been successfully used to monitor drift ratios [1, Panagitou et al. (Seismic Response of ReinForced Concrete Wall Buildings, 2006)], (Restrepo, pers. comm. 2007) – thus enabling future usefulness of GPS to all types of structures. Several levels of threshold drift ratios can be postulated in order to make decisions for inspections and/or occupancy. Experience with data acquired from both accelerometers and GPS deployments indicates that they are reliable and provide pragmatic alternatives to alert the owners and other authorized parties to make informed decisions and select choices for pre-defined actions following significant events. Furthermore, recent adoption of such methods by financial and industrial enterprises is testimony to their viability.

Book chapter↗

USGS2008

Finite-fault analysis of the 2004 Parkfield, California, earthquake using P nl waveforms

We apply a kinematic finite-fault inversion scheme to P nl displacement waveforms recorded at 14 regional stations (Δ<2°) to recover the distribution of coseismic slip for the 2004 Parkfield earthquake using both synthetic Green’s functions (SGFs) calculated for one-dimensional (1D) crustal-velocity models and empirical Green’s functions (EGFs) based on the recordings of a single M w 5.0 aftershock. Slip is modeled on a rectangular fault subdivided into 2×2 km subfaults assuming a constant rupture velocity and a 0.5 sec rise time. A passband filter of 0.1–0.5 Hz is applied to both data and subfault responses prior to waveform inversion. The SGF inversions are performed such that the final seismic moment is consistent with the known magnitude ( M w 6.0) of the earthquake. For these runs, it is difficult to reproduce the entire P nl waveform due to inaccuracies in the assumed crustal structure. Also, the misfit between observed and predicted vertical waveforms is similar in character for different rupture velocities, indicating that neither the rupture velocity nor the exact position of slip sources along the fault can be uniquely identified. The pattern of coseismic slip, however, compares well with independent source models derived using other data types, indicating that the SGF inversion procedure provides a general first-order estimate of the 2004 Parkfield rupture using the vertical P nl records. The best-constrained slip model is obtained using the single-aftershock EGF approach. In this case, the waveforms are very well reproduced for both vertical and horizontal components, suggesting that the method provides a powerful tool for estimating the distribution of coseismic slip using the regional P nl waveforms. The inferred slip model shows a localized patch of high slip (55 cm peak) near the hypocenter and a larger slip area (~50 cm peak) extending between 6 and 20 km to the northwest.

California↗

USGS1993

Use of geophysical data to assess scour development

The development of scour holes in the Connecticut River near the new Baldwin Bridge has been documented by comparing geophysical records collected before (1989), during (1990), and after (1992) bridge construction. Eight piers that support the 570-m (meter) span over the Connecticut River were protected by 12-m wide cofferdams during construction. The maximum flow during the study was equivalent to a 3-year recurrence-interval flood, indicating no significant floods. Fathometer data indicate that deep scour holes, 1.5 to 6.4 m deep, developed north of piers 6, 7, and 8. Scour holes, less than 1.3 m-deep, developed south of these piers. The deepest scour hole was north of pier 7, where data show a flat river bottom in 1989, a scour 3.3-m deep in 1990, and a scour hole 6.4-m deep in 1992. Continuous seismic-profiling (CSP) data show that a 1.5 -m deep scour hole north of pier 6 in 1990 was filled in with 1.5-m of material by 1992. No infilling was detected in the scour holes north of piers 7 and 8. Numerous subbottom reflectors from geologic layers, up to 7.6 -m deep were identified in the CSP records.

Conference Paper↗

USGS2025

Near-fault amplification and ground motion variability during the 2019 Ridgecrest, California sequence

We estimate ground-motion variability near the 2019 M 7.1 Ridgecrest earthquake sequence. Accurate seismic hazard estimation requires understanding ground-motion spatial correlations, yet many studies lack the dense station coverage needed to resolve small-scale variability. The 2019 M 7.1 Ridgecrest earthquake sequence presents a unique opportunity to examine ground motions and their spatial correlations at a range of interstation distances. The permanent seismic network was augmented with hundreds of temporary stations including several fault-crossing nodal arrays. We compute the event ( δE i ) and within-event ( δW ij ) residuals from the observed peak ground velocity and peak ground acceleration data to isolate potential sources of ground-motion variability. We then compare δW ij between station pairs that record an event to understand the semivariance of the ground motion versus interstation distance. By fitting an exponential model to the semivariances, we determine a correlation range of 25 km for the Ridgecrest region. Although the exponential model fits the broad-scale increase of semivariance with interstation distance, we also observe smaller-scale trends. We find that ground motions are less correlated for station pairs that are near or across faults that ruptured during the 2019 Ridgecrest sequence. We also find large, positive median δW ij with relative values 2–3 times larger than nearby stations for individual stations’ near-fault traces. Near-fault amplification and greater ground-motion variability can delineate fault zones and may locally increase the seismic hazard.

California↗

USGS1989

Geochemical evidence for invasion of Kilauea's plumbing system by Mauna Loa magma

From the beginning of the study of Hawaiian volcanism there has been controversy over possible relationships between the neighbouring active volcanoes Mauna Loa and Kilauea 1–5 . Seismic activity, thought to reflect upward migration of magma, reveals that the magmatic plumbing systems apparently converge at depth to form a broad funnel within the mantle 6 . Although on rare occasions they have erupted concurrently, the brief historical eruptive record appears to show that when Kilauea is most active, Mauna Loa is in repose and vice versa, suggesting that they may be competing for the same magma supply 5,7 . Petrological, geochemical and isotope data, however, require a diametrically opposite conclusion. Distinct differences in major-element, trace-element and isotope compositions of lavas are regarded as compelling evidence that the two volcanoes have separate magmatic plumbing systems, supplied by parental magmas from physically and geochemically distinct mantle sources 8–13 . Here we present preliminary geochemical data which show that in the past 2,000 years Kilauea has erupted a spectrum of lava compositions resembling historical Kilauea lavas at one end and Mauna Loa lavas at the other. We discuss the cause of this diversity, and speculate that magma from Mauna Loa may have invaded Kilauea's 'high-level' magmatic plumbing system.

Hawaii↗

USGS2024

Post-glacial stratigraphy and late Holocene record of great Cascadia earthquakes in Ozette Lake, Washington, USA

Ozette Lake is an ~100-m-deep coastal lake located along the outer coast of the Olympic Peninsula (Washington, USA); it is situated above the locked portion of the northern Cascadia megathrust but also relatively isolated from active crustal faults and intraslab earthquakes. Here we present a suite of geophysical and geological evidence for earthquake-triggered mass transport deposits (MTDs) and related turbidite deposition in Ozette Lake since ca. 14 ka. Comprehensive high-resolution bathymetry data, seismic reflection profiles, and sediment cores are used to characterize the post-glacial stratigraphic framework and examine paleoseismic evidence in the lacustrine sediments. Stacked sequences of MTDs along the steep eastern flanks of the lake appear to grade basin-ward from thick, chaotic, blocky masses to thin, parallel-bedded turbidite beds. The discrete turbidite event layers are separated by fine-grained (silt and clay) lake sedimentation. The event layers are observed throughout the lake, but the physical characteristics of the deposits vary considerably depending on proximity to primary depocenters, steep slopes, and subaqueous deltas. A total of 30–34 event deposits are observed in the post-glacial record. Radiometric dating was used to reconstruct a detailed sedimentation history over the last ~5.5 k.y., develop an age model, and estimate the recurrence (365–405 yr) for the most recent 12 event layers. Based on sedimentological characteristics, temporal overlap with other regional paleoseismic chronologies, and recurrence estimates, at least 10 of the dated event layers appear to be sourced from slope failures triggered by intense shaking during megathrust ruptures; the recurrence interval for these 10 events is 440–560 yr. Thus, Ozette Lake contains one of the longest and most robust geological records of repeated shaking along the northern Cascadia subduction zone.

Washington↗

USGS2026

How to determine an earthquake rate budget? A comparison of geodetic, geologic, and seismologic moment rates

How much tectonic geodetic strain is accommodated as earthquakes? Can estimates of tectonic geodetic strain be used in probabilistic seismic hazard analyses? Understanding the balance of moment accumulation (i.e., geodetic moment) and accommodation (i.e., geologic and seismologic moment) is a necessary step toward leveraging corrected geodetic strain rates to quantify earthquake budgets. We investigate these questions using updated geodetic, geologic, and seismologic datasets compiled for the western United States (WUS) portion of the 2023 U.S. National Seismic Hazard Model (NSHM23‐WUS) to provide new views of moment rates across the WUS. We compare moment rates using a floating footprint approach across the extent of the NSHM23‐WUS fault sections database. We make these comparisons using “moment rate deviation (MRD),” which is defined as a surplus or deficit of geodetic moment rate relative to the sum of geologic and seismologic moment rates. We find that, in general, higher strain rate areas of the WUS (i.e., plate boundary) have smaller values of MRD, meaning that geodetic moment rates approximate the earthquake record preserved by geologic and seismologic moment rates well. In contrast, the lower strain rate, eastern portions of our analysis domain (i.e., intraplate) have very high values of MRD, with geodetic moment rates exceeding measured geologic and seismologic moment rates. We find that geodetic moment rates appear to be representative of the earthquake budget in relatively well‐characterized, interplate regions, and geodetic estimates of off‐fault deformation could be considered in seismic hazard analyses where MRD is minimized.

western United States↗

USGS2007

A record of large earthquakes on the southern Hayward fault for the past 1800 years

This is the second article presenting evidence of the occurrence and timing of paleoearthquakes on the southern Hayward fault as interpreted from trenches excavated within a sag pond at the Tyson's Lagoon site in Fremont, California. We use the information to estimate the mean value and aperiodicity of the fault's recurrence interval (RI): two fundamental parameters for estimation of regional seismic hazard. An earlier article documented the four most recent earthquakes, including the historic 1868 earthquake. In this article we present evidence for at least seven earlier paleoruptures since about A.D. 170. We document these events with evidence for ground rupture, such as the presence of blocky colluvium at the base of the main trace fault scarp, and by corroborating evidence such as simultaneous liquefaction or an increase in deformation immediately below event horizons. The mean RI is 170 ?? 82 yr (1??, standard deviation of the sample), aperiodicity is 0.48, and individual intervals may be expected to range from 30 to 370 yr (95.4% confidence). The mean RI is consistent with the recurrence model of the Working Group on California Earthquake Probabilities (2003) (mean, 161 yr; range, 99 yr [2.5%]; 283 yr [97.5%]). We note that the mean RI for the five most recent events may have been only 138 ?? 58 yr (1??). Hypothesis tests for the shorter RI do not demonstrate that any recent acceleration has occurred compared to the earlier period or the entire 1800-yr record, principally because of inherent uncertainties of the event ages.

Bulletin of the Seismological Society of America↗

USGS2021

Onshore flow characteristics of the 1755 CE Lisbon tsunami: Linking forward and inverse numerical modeling

The 1755 CE Lisbon earthquake triggered the largest historical tsunami ever impacting the Atlantic coasts of Europe. Despite recent efforts to better understand this event, there are still unanswered questions about the location of its epicenter and whether physical and historical evidences are in agreement. Inverse modeling using tsunami sediments can be applied to quantify onshore flow characteristics. Forward numerical modeling is also a powerful tool capable of simulating tsunami hydrodynamics and the induced sediment transport. This work presents novel results from a combination of inverse and forward modeling to assess tsunami characteristics onshore. The study site is located on the Portuguese southern coast, at the Salgados lowland where inverse modeling was performed using TsuSedMod ( Jaffe and Gelfenbaum, 2007 ) based on data retrieved from sediment samples. Forward modeling, including tsunami generation and propagation, was performed using the FLOW module of Delft3D suite model. Onshore topography was corrected for the 1755 CE scenario based on extensive tsunami sedimentary deposit thickness data. The tsunami source was chosen based on recent results from the authors that pointed to a good correlation between modeled and field tsunami data for the Marques de Pombal Fault (MPF), Horseshoe Fault (HSF) and a hypothetical scenario represented by a simple combination between Gorringe Bank and Horseshoe Fault (Scenario 1 - SC1). Results from inverse model show tsunami onshore average speed varying from 7.3 up to 9.3 m/s and shear velocities from 0.52 up to 0.66 m/s. Forward modeling results show a wide variation according to the seismic source and tsunami onshore velocities can range from around 7 m/s when considering MPF to even an absence of inundation (SC1). The good agreement between both modeling approaches estimating tsunami velocity confirms the potential of numerical modeling coupled with geological records to improve the understanding of historical events.

Marine Geology↗

USGS2020

Local earthquake Vp and Vs tomography in the Mount St. Helens region with the iMUSH broadband array

We present new 3-D P wave and S wave velocity models of the upper 20 km of the Mount St. Helens (MSH) region. These were obtained using local-source arrival time tomography from earthquakes and explosions recorded at 70 broadband stations deployed as part of the imaging Magma Under St. Helens (iMUSH) project and augmented by several data sets. Principal features of our models include (1) low P wave and S wave velocities along the St. Helens seismic zone to depths of at least 20 km corresponding to high conductivity imaged by iMUSH magnetotelluric studies. This delineates a zone of weakness that magma can exploit at the location of MSH; (2) a 5- to 7-km diameter, 6–15 km deep, 3–6% negative P wave and S wave velocity anomaly beneath MSH, consistent with previous estimates of the source region for recent eruptions. We interpret this as a magma storage region containing up to 15–20 km 3 of partial melt, which is about 5 times more than the largest documented eruption at MSH; (3) a broad region of low P wave velocity below 10-km depth extending between Mount Adams and Mount Rainier along and to the east of the main Cascade arc, which is likely due to high-temperature arc crust and possible presence of fluids or melt; (4) several anomalies associated with surface-mapped features, including high-velocity igneous units such as the Spud Mountain and Spirit Lake plutons and low velocities in the Chehalis sedimentary basin and the Indian Heaven volcanic field. Our results place further constraints on the geometry of these features at depth.

Washington↗

USGS2012

Seismic guided waves trapped in the fault zone of the Landers, California, earthquake of 1992

A mobile seismic array of seven stations was deployed at 11 sites along the fault trace of the M 7.4 Landers earthquake of June 28, 1992, with a maximum offset of 1 km from the trace. We found a distinct wave train with a relatively long period following the S waves that shows up only when both the stations and the events are close to the fault trace. This wave train is interpreted as a seismic guided wave trapped in a low‐velocity fault zone. To study the distribution of amplitude of the guided waves with distance from the fault trace and also their attenuation with travel distance along the fault zone, we eliminated source and recording site effects by the coda normalization method. The normalized amplitudes of guided waves show a spectral peak at 3–4 Hz, which decays sharply with distance from the fault trace. Spectral amplitudes at high frequencies (8–15 Hz) show an opposite trend, increasing with distance from the fault trace. The normalized amplitudes of guided waves at 3–4 Hz also show a systematic decrease with hypocentral distance along the fault zone, from which we infer an apparent Q of 50. In order to confirm the existence of the guided waves, a dense array of 31 stations was deployed at one of the 11 sites. The resultant records revealed unequivocal evidence for the existence of guided waves associated with the fault zone. By modeling the waveforms as S waves trapped in a low‐velocity waveguide sandwiched between two homogeneous half‐spaces with velocity V s = 3.0 km/s, we infer a waveguide width of about 180 m, a shear velocity of 2.0–2.2 km/s, and a Q of ∼50. Hypocenters of aftershocks with clear guided waves show a systematic distribution both laterally and with depth delineating the extent of the low‐velocity fault zone in three dimensions. We find that the zone extends to a depth of at least 10 km. This zone apparently continues to the south across the Pinto Mountain fault because guided waves are observed at stations north of the Pinto Mountain fault for earthquakes with epicenters south of it. On the other hand, the zone appears to be discontinuous at the fault bend located about 20 km north of the mainshock epicenter; guided waves were observed for stations and epicenters which are located on the same sides of the fault bend but not for those on the opposite sides.

California↗

USGS1980

Driving- stress waveform and the determination of rock internal friction by the stress-strain curve method.

Harmonic distortion in the stress-time function applied to rock specimens affects the measurement of rock internal friction in the seismic wave periods by the stress-strain hysteresis loop method. If neglected, the harmonic distortion can cause measurements of rock internal friction to be in error by 3O% in the linear range. The stress-time function therefore must be recorded and Fourier analysed for correct interpretation of the experimental data. Such a procedure would also yield a value for internal friction at the higher harmonic frequencies.-Author

Geophysical Journal of the Royal Astronomical Soci↗

USGS2020

Short and long-term movement of mudflows of the Mississippi River Delta Front and their known and potential impacts on oil and gas infrastructure

Mudflows on the Mississippi River Delta Front (MRDF) are recognized hazards to oil and gas infrastructure in the shallow (20 – 300 m water depth) Gulf of Mexico. Preconditioning of the seafloor for failure results from high sedimentation rates coupled with slope over-steepening, under-consolidation, and abundant biogenic gas production. Catastrophic failure of production platforms and pipelines due to seafloor displacement during infrequent large hurricanes such as Camille in 1969 and Ivan in 2004, point to cyclical loading of the seafloor by waves as a primary movement trigger. Due to data limitations, the role of smaller storms and background oceanographic processes in driving seafloor movement have remained largely unconstrained, but are thought to contribute to significant seafloor change. With the aid of new high-resolution multibeam mapping and seismic reflection profiling across sections of the MRDF, several moving features within the deforming delta-front environment are investigated and potential hazards to infrastructure installed and adjacent to the region are discussed. Via repeat mapping surveys of selected areas and records of changing shipwreck locations, we highlight significant seafloor displacement across annual to decadal timescales. For example, individual blocks mapped within mudflow gullies adjacent to Southwest Pass show downslope transport of more than 80 m in a single year, while the S.S. Virginia, a 153 m-long oil tanker sunk in 1942 has been relocated and found to have moved downslope more than 400 m in 14 years, without a major hurricane (> Category 2) passing through the region.

Louisiana↗