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At least 523 records · Page 29Linked to original sources
USGS2016

Nutrient dynamics of the Delta: Effects on primary producers

Increasing clarity of Delta waters, the emergence of harmful algal blooms, the proliferation of aquatic water weeds, and the altered food web of the Delta have brought nutrient dynamics to the forefront. This paper focuses on the sources of nutrients, the transformation and uptake of nutrients, and the links of nutrients to primary producers. The largest loads of nutrients to the Delta come from the Sacramento River with the San Joaquin River seasonally important, especially in the summer. Nutrient concentrations reflect riverine inputs in winter and internal biological processes during periods of lower flow with internal nitrogen losses within the Delta estimated at approximately 30% annually. Light regime, grazing pressure, and nutrient availability influence rates of primary production at different times and locations within the Delta. The roles of the chemical form of dissolved inorganic nitrogen in growth rates of primary producers in the Delta and the structure of the open-water algal community are currently topics of much interest and considerable debate. Harmful algal blooms have been noted since the late 1990s, and the extent of invasive aquatic macrophytes (both submerged and free-floating forms) has increased especially during years of drought. Elevated nutrient loads must be considered in terms of their ability to support this excess biomass. Modern sensor technology and networks are now deployed that make high-frequency measurements of nitrate, ammonium, and phosphate. Data from such instruments allow a much more detailed assessment of the spatial and temporal dynamics of nutrients. Four fruitful directions for future research include utilizing continuous sensor data to estimate rates of primary production and ecosystem respiration, linking hydrodynamic models of the Delta with the transport and fate of dissolved nutrients, studying nutrient dynamics in various habitat types, and exploring the use of stable isotopes to trace the movement and fate of effluent-derived nutrients.

California↗
USGS2007

A new towed platform for the unobtrusive surveying of benthic habitats and organisms

Maps of coral ecosystems are needed to support many conservation and management objectives, as well as research activities. Examples include ground-truthing aerial and satellite imagery, characterizing essential habitat, assessing changes, and monitoring the progress of restoration efforts. To address some of these needs, the U.S. Geological Survey developed the Along-Track Reef-Imaging System (ATRIS), a boat-based sensor package for mapping shallow-water benthic environments. ATRIS consists of a digital still camera, a video camera, and an acoustic depth sounder affixed to a moveable pole. This design, however, restricts its deployment to clear waters less than 10 m deep. To overcome this limitation, a towed version has been developed, referred to as Deep ATRIS. The system is based on a light-weight, computer-controlled, towed vehicle that is capable of following a programmed diving profile. The vehicle is 1.3 m long with a 63-cm wing span and can carry a wide variety of research instruments, including CTDs, fluorometers, transmissometers, and cameras. Deep ATRIS is currently equipped with a high-speed (20 frames · s-1) digital camera, custom-built light-emitting-diode lights, a compass, a 3-axis orientation sensor, and a nadir-looking altimeter. The vehicle dynamically adjusts its altitude to maintain a fixed height above the seafloor. The camera has a 29° x 22° field-of-view and captures color images that are 1360 x 1024 pixels in size. GPS coordinates are recorded for each image. A gigabit ethernet connection enables the images to be displayed and archived in real time on the surface computer. Deep ATRIS has a maximum tow speed of 2.6 m · s-1and a theoretical operating tow-depth limit of 27 m. With an improved tow cable, the operating depth can be extended to 90 m. Here, we present results from the initial sea trials in the Gulf of Mexico and Biscayne National Park, Florida, USA, and discuss the utility of Deep ATRIS for map-ping coral reef habitats. Several example mosaics illustrate the high-quality imagery that can be obtained with this system. The images also reveal the potential for unobtrusive animal observations; fish and sea turtles are unperturbed by the presence of Deep ATRIS

Florida↗
USGS2004

Estimates of fetch-induced errors in Bowen-ratio energy-budget measurements of evapotranspiration from a prairie wetland, Cottonwood Lake Area, North Dakota, USA

Micrometeorological measurements of evapotranspiration ( ET ) often are affected to some degree by errors arising from limited fetch. A recently developed model was used to estimate fetch-induced errors in Bowen-ratio energy-budget measurements of ET made at a small wetland with fetch-to-height ratios ranging from 34 to 49. Estimated errors were small, averaging −1.90%±0.59%. The small errors are attributed primarily to the near-zero lower sensor height, and the negative bias reflects the greater Bowen ratios of the drier surrounding upland. Some of the variables and parameters affecting the error were not measured, but instead are estimated. A sensitivity analysis indicates that the uncertainty arising from these estimates is small. In general, fetch-induced error in measured wetland ET increases with decreasing fetch-to-height ratio, with increasing aridity and with increasing atmospheric stability over the wetland. Occurrence of standing water at a site is likely to increase the appropriate time step of data integration, for a given level of accuracy. Occurrence of extensive open water can increase accuracy or decrease the required fetch by allowing the lower sensor to be placed at the water surface. If fetch is highly variable and fetch-induced errors are significant, the variables affecting fetch (e.g., wind direction, water level) need to be measured. Fetch-induced error during the non-growing season may be greater or smaller than during the growing season, depending on how seasonal changes affect both the wetland and upland at a site.

North Dakota↗
USGS2009

Suggested notation conventions for rotational seismology

We note substantial inconsistency among authors discussing rotational motions observed with inertial seismic sensors (and much more so in the broader topic of rotational phenomena). Working from physics and other precedents, we propose standard terminology and a preferred reference frame for inertial sensors (Fig. 1) that may be consistently used in discussions of both finite and infinitesimal observed rotational and translational motions in seismology and earthquake engineering. The scope of this article is limited to observations because there are significant differences in the analysis of finite and infinitesimal rotations, though such discussions should remain compatible with those presented here where possible. We recommend the general use of the notation conventions presented in this tutorial, and we recommend that any deviations or alternatives be explicitly defined.

Bulletin of the Seismological Society of America↗
USGS2009

Recording rotational and translational ground motions of two TAIGER explosions in northeastern Taiwan on 4 March 2008

Two explosions were set off on 4 March 2008 at the N3 explosion site in northeastern Taiwan. The code name for the first shot with 3000 kg explosives is N3P and that for the second shot with 750 kg explosives is N3. To record these two explosions, 8 triaxial rotational sensors, 13 triaxial accelerometers, and 12 six-channel, 24 bit dataloggers with Global Positioning System receivers were deployed to continuously record several hours before and after the explosions. These instruments were installed at about 250 m (1 station), 500 m (11 stations), and 600 m (1 station) from the explosions. The 11 stations form a center array with station spacing of about 5 m. Except for one rotational sensor, onscale records were obtained. Although the N3P shot used four times larger amounts of explosives than those used for the N3 shot, the peak ground translational acceleration and rotational velocity at the 13 station sites from the N3P shot are only about 1.5 times larger than those for the N3 shot. We also observed large variations (by tens of percent) of translational accelerations and rotational velocities at the center array with station spacing of about 5 m. The largest peak rotational velocity was observed for the x component: 2.74 and 1.75 mrad/sec at a distance of 254 m from the N3P and N3 shots, respectively. The main purpose of this article is to document our recordings of rotational and translation motions from two explosions in Taiwan and to release the data online for open access. The translational acceleration data from this experiment have been analyzed by Langston et al. (2009) , and we plan to submit an article with analysis of the rotational velocity data in the future.

Bulletin of the Seismological Society of America↗
USGS2009

Along-Arc and Back-Arc Attenuation, Site Response, and Source Spectrum for the Intermediate-Depth 8 January 2006 M 6.7 Kythera, Greece, Earthquake

An M 6.7 intermediate-depth (66 km), in-slab earthquake occurring near the island of Kythera in Greece on 8 January 2006 was well recorded on networks of stations equipped with acceleration sensors and with broadband velocity sensors. All data were recorded digitally using recording instruments with resolutions ranging from almost 11 to 24 bits. We use data from these networks to study the distance dependence of the horizontal-component Fourier acceleration spectra (FAS) and horizontal-component pseudoabsolute response spectral acceleration (PSA). For purposes of simulating motions in the future, we parameterize the distance decay using several forms of the geometrical-spreading function, for each of which we derive Q as a function of frequency. By extrapolating the distance decay back to 1 km, we obtain a reference spectrum that can be used in future simulations. This spectrum requires a more complicated spectral shape than the classic single-corner-frequency model; in particular, there appears to be an enhancement of motion around 0.2-0.3 Hz that may be due to the radiation of a 3-5 sec pulse from the source. We infer a ?? 0 value of about 0.055 sec for rock stations and a stress parameter in the range of 400-600 bars. We also find distinctive differences in the site response of stations on soft soil and soil; both the FAS and the 5% damped PSA amplifications have similar peak amplitudes (about 2 and 4 for soil and soft-soil sites, respectively, relative to the rock sites) at similar frequencies (between about 0.4 and 2.0 Hz, with the soft-soil amplifications peaking at somewhat lower frequencies than the soil amplifications). One of the most distinctive features of the data is the clear difference in the motions for along-arc and back-arc stations, with the former being significantly higher than the latter over a broad range of frequencies at distances beyond about 250 km. The motions from the Kythera earthquake are roughly comparable to those from intermediate-depth earthquakes elsewhere, but they appear to be significantly higher than those from recordings of shallow earthquakes in Greece of comparable magnitude and hypocentral distance.

Bulletin of the Seismological Society of America↗
USGS2011

A Comparison of seismic instrument noise coherence analysis techniques

The self-noise of a seismic instrument is a fundamental characteristic used to evaluate the quality of the instrument. It is important to be able to measure this self-noise robustly, to understand how differences among test configurations affect the tests, and to understand how different processing techniques and isolation methods (from nonseismic sources) can contribute to differences in results. We compare two popular coherence methods used for calculating incoherent noise, which is widely used as an estimate of instrument self-noise (incoherent noise and self-noise are not strictly identical but in observatory practice are approximately equivalent; Holcomb, 1989; Sleeman et al., 2006). Beyond directly comparing these two coherence methods on similar models of seismometers, we compare how small changes in test conditions can contribute to incoherent-noise estimates. These conditions include timing errors, signal-to-noise ratio changes (ratios between background noise and instrument incoherent noise), relative sensor locations, misalignment errors, processing techniques, and different configurations of sensor types.

Bulletin of the Seismological Society of America↗
USGS2014

Rapid earthquake characterization using MEMS accelerometers and volunteer hosts following the M 7.2 Darfield, New Zealand, Earthquake

We test the feasibility of rapidly detecting and characterizing earthquakes with the Quake‐Catcher Network (QCN) that connects low‐cost microelectromechanical systems accelerometers to a network of volunteer‐owned, Internet‐connected computers. Following the 3 September 2010 M 7.2 Darfield, New Zealand, earthquake we installed over 180 QCN sensors in the Christchurch region to record the aftershock sequence. The sensors are monitored continuously by the host computer and send trigger reports to the central server. The central server correlates incoming triggers to detect when an earthquake has occurred. The location and magnitude are then rapidly estimated from a minimal set of received ground‐motion parameters. Full seismic time series are typically not retrieved for tens of minutes or even hours after an event. We benchmark the QCN real‐time detection performance against the GNS Science GeoNet earthquake catalog. Under normal network operations, QCN detects and characterizes earthquakes within 9.1 s of the earthquake rupture and determines the magnitude within 1 magnitude unit of that reported in the GNS catalog for 90% of the detections.

Darfield↗
USGS2016

Developments in new fluid rotational seismometers: Instrument performance and future directions

In this article we describe prototype designs and tests for low-cost rota- tional medium- and strong-motion seismometers using three types of proof mass (two liquid and one solid) and a number of transducer configurations. This article describes the third set of designs and tests in our development program. The details of our results for most of these are in the E electronic supplement to this article, whereas here we concentrate on three of the most promising and representative design combinations. Most of our results pertain to sensors with water or silicon oil as the proof mass, though we also tested a torsion-bar design with a solid proof mass. We find that most mass–transducer combinations lead to output proportional to rotational acceleration, with varying degrees of fidelity. Most combinations we tested can be dismissed from further development for reasons of performance or inconvenience during analysis of acceleration response (compare with E electronic supplement). In this article, we describe three of the more promising combinations, one each for the three types of response functions we measured. Of these three, one mass–transducer combination in particular (a hinged sensing element and capacitive transduction) has output voltage closely proportional to rotational displacement (angle) over a wide frequency range; such displacement proportionality obviates two of the integration steps normally re- quired to solve for continuum single-point motions or correct for tilt-induced errors in horizontal translational sensors. Thus, although we illustrate two other designs of some promise, we propose a new design that follows this displacement-proportional path while increasing the device’s sensitivity to on-axis rotations, improving its manu- facturing ease and lowering its sensitivity to translational motions.

Bulletin of the Seismological Society of America↗
USGS2017

Detection and characterization of pulses in broadband seismometers

Pulsing - caused either by mechanical or electrical glitches, or by microtilt local to a seismometer - can significantly compromise the long‐period noise performance of broadband seismometers. High‐fidelity long‐period recordings are needed for accurate calculation of quantities such as moment tensors, fault‐slip models, and normal‐mode measurements. Such pulses have long been recognized in accelerometers, and methods have been developed to correct these acceleration steps, but considerable work remains to be done in order to detect and correct similar pulses in broadband seismic data. We present a method for detecting and characterizing the pulses using data from a range of broadband sensor types installed in the Global Seismographic Network. The technique relies on accurate instrument response removal and employs a moving‐window approach looking for acceleration baseline shifts. We find that pulses are present at varying levels in all sensor types studied. Pulse‐detection results compared with average daily station noise values are consistent with predicted noise levels of acceleration steps. This indicates that we can calculate maximum pulse amplitude allowed per time window that would be acceptable without compromising long‐period data analysis.

Bulletin of the Seismological Society of America↗
USGS2017

Improvements in absolute seismometer sensitivity calibration using local earth gravity measurements

The ability to determine both absolute and relative seismic amplitudes is fundamentally limited by the accuracy and precision with which scientists are able to calibrate seismometer sensitivities and characterize their response. Currently, across the Global Seismic Network (GSN), errors in midband sensitivity exceed 3% at the 95% confidence interval and are the least‐constrained response parameter in seismic recording systems. We explore a new methodology utilizing precise absolute Earth gravity measurements to determine the midband sensitivity of seismic instruments. We first determine the absolute sensitivity of Kinemetrics EpiSensor accelerometers to 0.06% at the 99% confidence interval by inverting them in a known gravity field at the Albuquerque Seismological Laboratory (ASL). After the accelerometer is calibrated, we install it in its normal configuration next to broadband seismometers and subject the sensors to identical ground motions to perform relative calibrations of the broadband sensors. Using this technique, we are able to determine the absolute midband sensitivity of the vertical components of Nanometrics Trillium Compact seismometers to within 0.11% and Streckeisen STS‐2 seismometers to within 0.14% at the 99% confidence interval. The technique enables absolute calibrations from first principles that are traceable to National Institute of Standards and Technology (NIST) measurements while providing nearly an order of magnitude more precision than step‐table calibrations.

Bulletin of the Seismological Society of America↗
USGS2017

Effects of thermal variability on broadband seismometers: Controlled experiments, observations, and implications

Isolating seismic instruments from temperature fluctuations is routine practice within the seismological community. However, the necessary degree of thermal stability required in broadband installations to avoid generating noise or compromising the fidelity in the seismic records is largely unknown and likely application dependent. To quantify the temperature sensitivity of seismometers over a broad range of frequencies, we artificially induced local temperature changes on three different models of seismometers to measure the effect of thermal variations on seismometer output. We found that diurnal temperature changes above 0.002°C root mean square (rms) showed significant changes in velocity and acceleration output in comparison to thermally stable reference measurements. We also found that sensor incoherent self‐noise increased with temperature variation; these increases in noise can be modeled as 1 / f "> 1 / f noise (pink noise), and are unlikely to be easily corrected for. These experimental results are compared with the data from Incorporated Research Institutions for Seismology (IRIS) U.S. Geological Survey (USGS) Global Seismographic Network (GSN) station TUC (Tucson, Arizona). This station is well instrumented with temperature sensors and has three different broadband seismometers, each of which uses a different method of thermal isolation. We show that the water bricks and borehole installations give ample temperature attenuation to thermally isolate seismometers from diurnal thermal variability that would compromise seismic data. We find that seismometer installations that provide thermal stability below 0.002°C rms could help to improve long‐period vertical seismic data across the GSN by decreasing temperature‐driven 1 / f "> 1 / f noise.

Bulletin of the Seismological Society of America↗
USGS2022

Seismic background noise levels across the continental United States from USArray Transportable Array: The influence of geology and geography

Since 2004, the most complete estimate of background noise levels across the continental U.S. was attained using 61 broadband seismic stations to calculate power spectral density (PSD) probability density functions. To improve seismic noise estimates across the U.S., we examine vertical component seismic data from the EarthScope USArray Transportable Array seismic network that rolled across the U.S. and southeastern Canada between 2004 and 2015 and form a large (10 TB) PSD database from 1679 stations that contains no smoothing or binning of the spectral estimates. Including station outages, our database has a mean of 98.9% data completeness, and we present maps showing the spatial and temporal variability of seismic noise in six bands of interest between 0.2- and 75-s period. At 0.2 s period, seismic noise across the eastern U.S. is predominantly anthropogenically generated and may be subsequently amplified more than 20 decibels in the sandy and water-saturated sediments of the southeastern U.S. Coastal Plain and Mississippi Embayment. In these sediments, 1 s noise shows similar amplification and is generated through a variety of mechanisms including cultural activity throughout Kentucky and the southeastern Appalachian Mountains, lake waves around the Great Lakes, and ocean waves throughout New England, the Pacific Northwest, and Florida. Both 0.2 and 1 s noise levels are the lowest in the Intermountain West portion of the U.S. We attribute this to a combination of installations on crystalline rocks and reduced population density. Finally, we find that sensors emplaced in sandy, water-saturated sediments observe median, diurnal variations in vertical component power at 18 to 75 s period, which we infer arise through local deformation driven by pressure variations. Ultimately, our results underscore that for shallow (<5 m depth) sensor installation, bedrock provides superior broadband noise performance compared to unconsolidated sediments.

Bulletin of the Seismological Society of America↗
USGS2015

Self-noise models of five commercial strong-motion accelerometers

Strong‐motion accelerometers provide onscale seismic recordings during moderate‐to‐large ground motions (e.g., up to tens of m/s 2 peak). Such instruments have played a fundamental role in improving our understanding of earthquake source physics (Bock etal. , 2011), earthquake engineering (Youd et al. , 2004), and regional seismology (Zollo et al. , 2010). Although strong‐motion accelerometers tend to have higher noise levels than high‐quality broadband velocity seismometers, their higher clip‐levels provide linear recordings at near‐field sites even for the largest of events where a collocated broadband sensor would no longer be able to provide onscale recordings (Clinton and Heaton, 2002). Recently, the seismological community has begun to make use of strong‐motion accelerometer data even in the absence of large ground motions (e.g., Tibuleac et al. , 2011). The noise floor of the instruments often limits the usefulness of strong‐motion accelerometer data in such studies, because it obscures first arrivals or can make the traces dominated by noise. When a strong‐motion accelerometer is deployed in a quiet setting, the noise floors of the digitizer and the accelerometer tend to dominate the other noise sources (Cauzzi and Clinton, 2013). This situation is unlike that using broadband sensors, in which site conditions are typically the largest contributing source of noise in seismic data, especially at long periods (Wilson et al. , 2002). With the widespread deployment of strong‐motion accelerometers recorded on high resolution digitizers, it is now possible to get continuous high‐rate acceleration data in which the digitizer noise is not the dominant noise source (Cauzzi and Clinton, 2013). To better characterize the noise of a number of commonly deployed accelerometers in a standardized way, we conducted noise measurements on five different models of strong‐motion accelerometers. Our study was limited to traditional accelerometers (Fig. 1) and is in no way exhaustive.

Seismological Research Letters↗
USGS2015

Surface monitoring of microseismicity at the Decatur, Illinois, CO2 sequestration demonstration site

Sequestration of CO2 into subsurface reservoirs can play an important role in limiting future emission of CO2 into the atmosphere (e.g., Benson and Cole, 2008). For geologic sequestration to become a viable option to reduce greenhouse gas emissions, large-volume injection of supercritical CO2 into deep sedimentary formations is required. These formations offer large pore volumes and good pore connectivity and are abundant (Bachu, 2003; U.S. Geological Survey Geologic Carbon Dioxide Storage Resources Assessment Team, 2013). However, hazards associated with injection of CO2 into deep formations require evaluation before widespread sequestration can be adopted safely (Zoback and Gorelick, 2012). One of these hazards is the potential to induce seismicity on pre-existing faults or fractures. If these faults or fractures are large and critically stressed, seismic events can occur with magnitudes large enough to pose a hazard to surface installations and, possibly more critical, the seal integrity of the cap rock. The Decatur, Illinois, carbon capture and storage (CCS) demonstration site is the first, and to date, only CCS project in the United States that injects a large volume of supercritical CO2 into a regionally extensive, undisturbed saline formation. The first phase of the Decatur CCS project was completed in November 2014 after injecting a million metric tons of supercritical CO2 over three years. This phase was led by the Illinois State Geological Survey (ISGS) and included seismic monitoring using deep borehole sensors, with a few sensors installed within the injection horizon. Although the deep borehole network provides a more comprehensive seismic catalog than is presented in this paper, these deep data are not publicly available. We contend that for monitoring induced microseismicity as a possible seismic hazard and to elucidate the general patterns of microseismicity, the U.S. Geological Survey (USGS) surface and shallow borehole network described below provides an adequate event detection threshold. The formation targeted for injection is the Mount Simon Sandstone, which is laterally extensive, has high porosity and permeability and has the potential to host future CCS projects due to its favorable hydrologic characteristics and proximity to industrial sources of CO2 (Birkholzer and Zhou, 2009). At Decatur, CO2, a byproduct of ethanol production at the Archer Daniels Midland (ADM) facility, is compressed to supercritical state and injected at 2.1 km depth into the 460 m thick Mount Simon Sandstone. This sandstone has varying properties, ranging from the lower, fine- to coarse-grained sandstone with high permeability and porosity, to the middle and upper Mount Simon, which consist of planar, cross-bedded layers of varied permeability and porosity (Leetaru and Freiburg, 2014). The changes in permeability and porosity within the Mount Simon Sandstone, due to depositional and diagenetic differences, create horizontal baffles, which inhibit vertical flow and restrict the injected CO2 to remain near the injection horizon (Bowen et al., 2011). The lowest portion of the Mount Simon Sandstone overlying the Precambrian rhyolite basement is the Pre-Mount Simon interval, generally < 15 m in thickness and composed of fine- to medium-grain size sandstone that is highly deformed (Leetaru and Freiburg, 2014). The basement rhyolite has a clayrich matrix and is fractured, with significant alterations within the fractures. The primary sealing cap rock is the Eau Claire Formation, a 100–150 m thick unit at a depth of roughly 1.69 km (Leetaru and Freiburg, 2014). The Maquoketa Shale Group and the New Albany Shale serve as secondary and tertiary seals at shallower depths of ∼820 and ∼650 m, respectively. The ISGS managed the Illinois Basin–Decatur Project (IBDP), a three-year project beginning in November 2011, during which carbon dioxide was injected at a rate of ∼1000 metric tons per day until November 2014 (Finley et al., 2011, 2013). ADM manages the Illinois Industrial CCS (ICCS) project, which will inject ∼3000 metric tons/day into a second injection well starting in the summer of 2015. The USGS began monitoring microseismicity with a 13- station seismic network at Decatur in July 2013 (Fig. 1). This network provides good detection capabilities and azimuthal (focal sphere) coverage for microseismicity with moment magnitudes (Mw) above about −0:5. Here, we report on 19 months of microseismicity monitoring at the Decatur CO2 sequestration site, which permits a detailed look at the evolution and character of injection-induced seismicity.

Illinois↗
USGS2017

Characterizing local variability in long‐period horizontal tilt noise

Horizontal seismic data are dominated by atmospherically induced tilt noise at long periods (i.e., 30 s and greater). Tilt noise limits our ability to use horizontal data for sensitive seismological studies such as observing free earth modes. To better understand the local spatial variability of long‐period horizontal noise, we observe horizontal noise during quiet time periods in the Albuquerque Seismological Laboratory (ASL) underground vault using four small‐aperture array configurations. Each array comprises eight Streckeisen STS‐2 broadband seismometers. We analyze the spectral content of the data using power spectral density and magnitude‐squared coherence (γ2‐coherence). Our results show a high degree of spatial variability and frequency dependence in the long‐period horizontal wavefield. The variable nature of long‐period horizontal noise in the ASL vault suggests that it might be highly local in nature and not easily characterized by simple physical models when overall noise levels are low, making it difficult to identify locations in the vault with lower horizontal noise. This variability could be limiting our ability to apply coherence analysis for estimating horizontal sensor self‐noise and could also complicate various indirect methods for removing long‐period horizontal noise (e.g., collocated rotational sensor or microbarograph).

New Mexico↗
USGS2018

The Albuquerque Seismological Lab WWSSN film chip preservation project

From 1961 to 1996, the Albuquerque Seismological Laboratory (ASL) installed and operated the World‐Wide Standardized Seismograph Network (WWSSN). Each station within the network consisted of three Benioff short‐period sensors and three Sprengnether Press‐Ewing long‐period sensors along with recording, timing, and calibration equipment. Approximately 3.7 million single‐day record film chips were created from station records (paper seismograms) covering the period from 1962 to 1978. Two almost complete copies of these film chips are still known to exist at the ASL and at the Lamont–Doherty Earth Observatory (LDEO) as well as a couple of partial sets in other locations. To better preserve the data on these film chips, a project to scan the film chips and to make these scans available through the Incorporated Research Institutions for Seismology (IRIS) was started by W. H. K. Lee. The initial focus was on scanning film chips from a collection of specific earthquakes and nuclear events as well as complete scans of a number of reference stations. However, additional scans containing seismograms useful for climate studies were also completed. As part of this report, we cataloged all of the scanned WWSSN film chips with the hope that it serves as useful documentation as to what film chips have been scanned and of the location of the scans themselves at the IRIS‐Data Management Center (DMC) archive page (see Data and Resources ).

Seismological Research Letters↗
USGS2023

Earthquake detection with tinyML

Earthquake detection is the critical first step in earthquake early warning (EEW) systems. For robust EEW systems, detection accuracy, detection latency, and sensor density are critical to providing real‐time earthquake alerts. Traditional EEW systems use fixed sensor networks or, more recently, networks of mobile phones equipped with microelectromechanical systems (MEMS) accelerometers. Internet of things edge devices, with built‐in tiny machine learning (tinyML) capable microcontrollers, and always‐on, internet‐connected, stationary MEMS accelerometers provide the opportunity to deploy ML‐based earthquake detection and warning using a single‐station approach at a global scale. Here, I test and evaluate tinyML deep learning algorithms for earthquake detection on a microcontroller. I show that the tinyML earthquake detection models can generalize to earthquakes outside the training set.

Seismological Research Letters↗