Geology topics

Research about Utah

Source-linked reports with geographic coverage including Utah.

At least 91 records · Page 5Linked to original sources

USGS2022

Conflicts among protected native birds and valuable sport fishes: Potential pelican predation effects

Reservoirs are examples of novel ecosystems that have developed into popular sport fisheries; these systems are also becoming seasonal refuges for migratory birds, including the piscivorous American white pelican ( Pelecanus erythrorhynchos ). We (1) investigated the proportion of cutthroat trout ( Oncorhynchus clarkii utah ) and other species consumed by pelicans, (2) compared whether pelicans have an adverse effect on cutthroat trout spawning movement, and (3) determined the importance of pelican predation relative to other sources of fish mortality in Strawberry Reservoir, Utah, USA. Pelican diet samples consisted of >85% Utah sucker ( Catostomus ardens ), 6% Utah chub ( Gila atraria ), and 3% cutthroat trout. Based on bioenergetics, we estimated that pelicans consumed 384–3020 individual cutthroat trout (0.17%–1.3% of population), in contrast to 14 166–27 196 nongame sucker and chub. Bird-related mortality rate ranged from 1% to 6% for stocked, PIT (passive integrated transponder)-tagged adult cutthroat trout and from 4% to 16% for subadult cutthroat trout. Based on these results, any management action taken to control pelican predation would need to be weighed against the benefits of nongame fish removal and the protected status of pelicans.

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USGS2022

Preliminary evidence of anticoagulant rodenticide exposure in American kestrels (Falco sparverius) in the western United States

Although there is extensive evidence of declines in the American Kestrel ( Falco sparverius ) population across North America, the cause of such declines remains a mystery. One hypothesized driver of decline is anticoagulant rodenticide (AR) exposure, which could potentially cause mortality or reduced fitness. We investigated AR exposure in wild American Kestrels in Utah, USA. We collected and tested for AR residues in liver samples ( n = 8) from kestrels opportunistically encountered dead and in blood samples ( n = 71) from live wild kestrels, both nestlings and adults. We found high detection rates in both tissues. Adult kestrels were more likely to exhibit exposure than juveniles sampled in nests. Three-quarters (six of eight) of tested liver samples from adult kestrels exhibited evidence of AR exposure. Additionally, liver samples ( n = 19) opportunistically collected from seven species of raptors within our study area had detectable levels of AR residues, with seven of eight raptor species evidencing exposure; across all raptors, five ARs were detected in liver samples, with brodifacoum the most prevalent, being found in over half (14 of 27) of samples. Over half (7 of 12) of the blood samples from adult kestrels had detectible levels of ARs, while only one of 59 juvenile nest samples tested positive. The difference in exposure rates between adults and juveniles could indicate differential exposure pathways by age class. Based on these findings, we recommend that ARs be further investigated as a potential cause of kestrel declines. Future research could focus on expanding sampling to provide sufficient sample sizes to test for potential nonlethal effects of AR exposure (e.g., fecundity, nesting success), identifying potential exposure pathways, and developing methods for passive sampling of ARs in excreta.

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USGS2021

Climatic controls on soil carbon accumulation and loss in a dryland ecosystems

Arid and semiarid ecosystems drive year-to-year variability in the strength of the terrestrial carbon (C) sink, yet there is uncertainty about how soil C gains and losses contribute to this variation. To address this knowledge gap, we embedded C-depleted soil mesocosms, containing litter or biocrust C inputs, within an in situ dryland ecosystem warming experiment. Over the course of one year, changes in microbial biomass and total soil organic C pools were monitored alongside hourly measurements of soil CO 2 flux. We also developed a biogeochemical model to explore the mechanisms that gave rise to observed soil C dynamics. Field data and model simulations demonstrated that water exerted much stronger control on soil biogeochemistry than temperature, with precipitation events triggering large CO 2 pulses and transport of litter- and biocrust-derived C into the soil profile. We expected leaching of organic matter would result in steady accumulation of C within the mineral soil over time. Instead, the size of the total organic C pool fluctuated throughout the year, largely in response to microbial growth: increases in the size of microbial biomass were negatively correlated with the quantity of C residing in the top 2 cm, where most biogeochemical changes were observed. Our data and models suggest that microbial responses to precipitation events trigger rapid metabolism of dissolved organic C inputs, which strongly limit accumulation of autotroph-derived C belowground. Accordingly, changes in the magnitude and/or frequency of precipitation events in this dryland ecosystem could have profound impacts on the strength of the soil C sink.

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USGS2021

Seasonal variation in resource selection by subadult golden eagles in the Great Basin Desert

Golden eagles Aquila chrysaetos are a long-lived and wide-ranging species believed to be stable or in slight decline across North America. Golden eagles have an extended subadult stage (4–5 years) that is critical to maintaining recruitment into the breeding population and population viability. Compared to adult golden eagles, the ecology of subadult golden eagles (hereafter, subadults) has received little attention. We investigated patterns of resource selection for subadults in the Great Basin Desert of the western United States during summer and winter, 2013–2019. We monitored 46 subadults with GPS transmitters and related locations (n = 99 037) with predictors hypothesized to influence seasonal patterns of space use with mixed-effects logistic regression. Subadults selected for ridges and upper slopes in summer and winter, but higher elevations in summer. Subadults showed weak selection for lower ridge density in summer, which was likely facilitated by selection for areas with greater thermal wind current potential. In contrast, subadults showed strong selection for higher ridge density in winter. Subadults selected areas further from roads in summer and closer to roads and electrical transmission lines in winter, which may be related to winter scavenging of road-killed ungulates. Resource selection functions suggested subadults selected for shrublands and woodlands in both seasons, but odds ratios revealed that during winter subadults avoided shrublands and increased selection of woodlands relative to summer. Subadults selected for areas with infrequent fires in both seasons; areas with frequent fires were avoided in summer but selected for in winter. Seasonal changes in resource selection suggested that subadults used woodlands more than expected, potentially reflecting spatial partitioning by subadults to lower-quality habitats to minimize competition with breeding adults during winter when energetic demands for thermoregulation were presumably higher and prey more limited.

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USGS2021

An opportunistic survey reveals an unexpected coronavirus diversity hotspot in North America

In summer 2020, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) was detected on mink farms in Utah. An interagency One Health response was initiated to assess the extent of the outbreak and included sampling animals from on or near affected mink farms and testing them for SARS-CoV-2 and non-SARS coronaviruses. Among the 365 animals sampled, including domestic cats, mink, rodents, raccoons, and skunks, 261 (72%) of the animals harbored at least one coronavirus. Among the samples that could be further characterized, 127 alphacoronaviruses and 88 betacoronaviruses (including 74 detections of SARS-CoV-2 in mink) were identified. Moreover, at least 10% ( n = 27) of the coronavirus-positive animals were found to be co-infected with more than one coronavirus. Our findings indicate an unexpectedly high prevalence of coronavirus among the domestic and wild free-roaming animals tested on mink farms. These results raise the possibility that mink farms could be potential hot spots for future trans-species viral spillover and the emergence of new pandemic coronaviruses.

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USGS2021

Utah prairie dog population dynamics on the Awapa Plateau: Precipitation, elevation, and plague

Utah prairie dogs (UPDs, Cynomys parvidens ) are colonial, herbivorous rodents listed under the Endangered Species Act as threatened. Little is known about UPD population dynamics at higher elevations in the species’ range. From 2013 through 2016, we studied UPDs on five colonies at 2,645 to 2,873 m elevation on the Awapa Plateau, Utah, USA. Primary production increases with precipitation and precipitation increases with elevation on the plateau. We hypothesized that UPD body condition, reproduction, survival, and population growth all would vary directly with precipitation and elevation. Each year, we live-trapped UPDs from late-Jun through Aug, weighing each UPD, aging it as adult or pup, measuring its right hind foot, marking it for unique identification, and releasing it at point of capture. Fleas from live-trapped UPDs and opportunistically collected rodent carcasses, and rodent carcasses themselves, were tested for the agent of sylvatic plague ( Yersinia pestis ), a lethal invasive pathogen. Adult UPD body condition (mass:foot) increased with elevation. In addition, UPD reproduction (pups:adults) and population growth (λ) increased with precipitation. Annual survival declined from 0.49 in 2013–2014 to 0.24 in 2015–2016. We captured 421 UPDs in 2013 but only 149 in 2016. Sylvatic plague may have contributed to population declines. Notwithstanding, plague detection (yes/no by colony and year) had no statistical effect on population growth or annual survival, raising suspicion about the predictive value of binary plague detection variables. Generally speaking, efforts to conserve UPDs may benefit from the restoration and preservation of large colonies at mesic sites.

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USGS2021

Trophic niches of native and nonnative fishes along a river-reservoir continuum

Instream barriers can constrain dispersal of nonnative fishes, creating opportunities to test their impact on native communities above and below these barriers. Deposition of sediments in a river inflow to Lake Powell, USA resulted in creation of a large waterfall prohibiting upstream movement of fishes from the reservoir allowing us to evaluate the trophic niche of fishes above and below this barrier. We expected niche overlap among native and nonnative species would increase in local assemblages downstream of the barrier where nonnative fish diversity and abundance were higher. Fishes upstream of the barrier had more distinct isotopic niches and species exhibited a wider range in δ 15 N relative to downstream. In the reservoir, species were more constrained in δ 15 N and differed more in δ 13 C, representing a shorter, wider food web. Differences in energetic pathways and resource availability among habitats likely contributed to differences in isotopic niches. Endangered Razorback Sucker ( Xyrauchen texanus ) aggregate at some reservoir inflows in the Colorado River basin, and this is where we found the highest niche overlap among species. Whether isotopic niche overlap among adult native and nonnative species has negative consequences is unclear, because data on resource availability and use are lacking; however, these observations do indicate the potential for competition. Still, the impacts of diet overlap among trophic generalists, such as Razorback Sucker, are likely low, particularly in habitats with diverse and abundant food bases such as river-reservoir inflows.

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USGS2021

Seismic wave propagation and basin amplification in the Wasatch Front, Utah

Ground‐motion analysis of more than 3000 records from 59 earthquakes, including records from the March 2020 M w "> M w 5.7 Magna earthquake sequence, was carried out to investigate site response and basin amplification in the Wasatch Front, Utah. We compare ground motions with the Bayless and Abrahamson (2019 ; hereafter, BA18) ground‐motion model (GMM) for Fourier amplitude spectra, which was developed on crustal earthquake records from California and other tectonically active regions. The Wasatch Front records show a significantly different near‐source rate of distance attenuation than the BA18 model, which we attribute to differences in (apparent) geometric attenuation. Near‐source residuals show a period dependence of this effect, with greater attenuation at shorter periods ( ⁠ T < 0.5    s "> T < 0.5 s ) and a correlation between period and the distance over which the discrepancy manifests ( ⁠ ∼ 20 – 50    km "> ∼ 20 – 50 km ⁠ ). We adjusted the recorded ground motions for these regional path effects and solved for station site terms using linear mixed‐effects regressions, with groupings for events and stations. We analyzed basin amplification by comparing the site terms with the basin geometry and basin depths from two seismic‐velocity models for the region. Sites over the deeper parts of the sedimentary basins are amplified by factors of 3–10, relative to sites with thin sedimentary cover, with greater amplification at longer periods ( ⁠ T ≳ 1    s "> T ≳ 1 s ). Average ground‐motion variability increases with period, and long‐period variability exhibits a slight increase at the basin edges. These results indicate regional seismic wave propagation effects requiring further study, and potentially a regionalized GMM, as well as highlight basin amplification complexities that may be incorporated into seismic hazard assessments.

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USGS2021

Drought resistance and resilience: The role of soil moisture–plant interactions and legacies in a dryland ecosystem

In many regions of the world, climate change is projected to reduce water availability through changes in the hydrological cycle, including more frequent and intense droughts, as well as seasonal shifts in precipitation. In water-limited ecosystems, such as drylands, lower soil water availability may exceed the adaptive capacity of many organisms, leading to cascading ecological effects during (concurrent effects) and after drought (legacy effects). The magnitude and duration of concurrent and legacy effects depends on drought intensity, duration and timing as well as the resistance and resilience of the ecosystem. Here, we investigated the effects of drought seasonality and plant community composition on two dominant perennial grasses, Achnatherum hymenoides (C 3 photosynthesis) and Pleuraphis jamesii (C 4 photosynthesis), in a dryland ecosystem. The experiment consisted of three precipitation treatments: control (ambient precipitation), cool-season drought (−66% ambient precipitation November–April) and warm-season drought (−66% ambient precipitation May–October), applied in two plant communities (perennial grasses with or without a large shrub, Ephedra viridis ) over a 3-year period. We examined the concurrent and legacy effects of seasonal drought on soil moisture, phenology and biomass. Drought treatments had strong concurrent and legacy effects on soil moisture, which impacted the phenology and biomass of the two grasses. Drought reduced growing season length by delaying green-up (cool-season drought) or advancing senescence (warm-season drought) and reduced biomass for both species. Biomass and phenology legacy effects from drought emerged in the second and third years of the experiment. While we observed differential sensitivity to drought legacies between the two grasses, we found limited evidence that shrub presence had interactive effects with the drought treatment. Synthesis . The results from this study highlight how abiotic and biotic legacies can develop and influence a community's resistance and resilience to subsequent droughts. When the frequency of repeated extreme events, such as recurring seasonal droughts, exceeds the capacity of organisms or ecosystems to recover (i.e. resilience), persistent drought legacies can reduce the resistance to subsequent drought events. Overall, these results highlight how drought legacies are a product of ecological resistance and resilience to past drought and can influence ecosystem vulnerability to future droughts.

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USGS2021

Potential Pb+2 mobilization, transport, and sequestration in shallow aquifers impacted by multiphase CO2 leakage: A natural analogue study from the Virgin River Basin in Southwest Utah

Geological carbon sequestration (GCS) is necessary to help meet emissions reduction goals, but groundwater contamination may occur if CO 2 and/or brine were to leak out of deep storage formations into the shallow subsurface. For this study, a natural analogue was investigated: in the Virgin River Basin of southwest Utah, water with moderate salinity and high CO 2 concentrations is leaking upward into shallow aquifers that contain heavy metal-bearing concretions. The aquifer system is comprised of the Navajo and Kayenta formations, which are pervasive across southern Utah and have been considered as a potential GCS injection unit where they are sufficiently deep. Numerical models of the site were constructed based on measured water chemistry and head distributions from previous studies. Simulations were used to improve understanding of the rate and distribution of the upwelling flow into the aquifers, and to assess the reactive transport processes that may occur if the upwelling fluids were to interact with a zone of iron oxide and other heavy metals, representing the concretions that are common in the area. Various mineralogies were tested, including one in which Pb +2 was adsorbed onto ferrihydrite, and another in which it was bound within a solid mixture of litharge (PbO) and hematite (Fe 2 O 3 ). Results indicate that metal mobilization depends strongly on the source zone composition and that Pb +2 transport can be naturally attenuated by gas phase formation and carbonate mineral precipitation. These findings could be used to improve risk assessment and mitigation strategies at geological carbon sequestration sites.

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USGS2021

The demographic and ecological factors shaping diversification among rare Astragalus species

Aim Evolutionary radiations are central to the origin and maintenance of biodiversity, yet we rarely understand how they are jointly shaped by demography and ecological opportunity. Astragalus is the largest plant genus in the world and is disproportionately comprised of rare species restricted to narrow geographic and ecological regions. Here, we explored the demographic and ecological mechanisms underlying patterns of diversification in a threatened Astragalus species complex endemic to a small desert region in the western United States. Location Southeast Utah, USA. Methods We used high‐throughput DNA sequencing to infer genetic structure, genetic diversity, and demographic history (i.e., the timing of population divergence, effective population sizes and gene flow) among Astragalus taxa. We performed landscape genetic analyses to quantify the relationships between genetic differentiation, geographic distance, and ecological distance based on bioclimatic and soil variables. Finally, we identified putative adaptive loci that show higher genetic differentiation between taxa than expected based on our inferred neutral demographic model. Results We found evidence of low gene flow between three highly differentiated taxa (currently delineated as A . iselyi , A . sabulosus var. sabulosus and A. sabulosus var. vehiculus ) that rapidly diverged from a small ancestral population near the beginning of the last glacial period. Genomic signatures revealed long‐term effective population sizes are 2–10× larger than recent census sizes, perhaps due to the maintenance of standing genetic variation through seed banks. Consistent with limited dispersal and local adaptation, genome‐wide patterns of differentiation are shaped by geographic distance (isolation‐by‐distance) and climate and soil variation (isolation‐by‐environment). Taxon‐specific adaptation is further supported by uncovering putative adaptive loci. Main Conclusions Our findings suggest that interactions between demography (i.e., dispersal limitations and seeds banks) and ecological opportunity (i.e., spatial and temporal environmental heterogeneity) may promote diversification, endemism, and rarity among closely related Astragalus species and similar plant clades distributed across complex landscapes.

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USGS2021

History of Great Salt Lake, Utah, USA: Since the termination of Lake Bonneville

During the past half century or so diverse histories of Great Salt Lake have been written from differing perspectives and all of them have contributed ideas and essential data. The published literature, however, can be confusing and misleading. In this chapter, we review and provide context for a number of those publications. This chapter is intended as a summary of what is known, what is not known, and what cannot be known with precision about the history of the lake. Great Salt Lake is the largest hydrographically closed lake in the Bonneville basin of northwestern Utah. It responds to both short-term weather and long-term climate. In the Lake Bonneville/Great Salt Lake lacustrine system, the end of Lake Bonneville at 13,000 yr BP marks the beginning of Great Salt Lake. The much larger and deeper lakes of the Bonneville lake cycle responded to the pluvial climate of oxygen isotope stage 2, but the warmer, drier climate of oxygen isotope stage 1 led to rapid fluctuations within a relatively narrow, well-documented elevation range, 5 m above and 9 m below the historical mean elevation of ~1280 m. Two exceptional but short-lived rises of Great Salt Lake to elevations higher than 5 m above ~1280 m have been documented —one during the Gilbert episode, which peaked about 11,600 yr BP near an elevation of 1295 m, and one to about 1289 m sometime after about 11,000 yr BP. The historical Great Salt Lake hydrograph (the past 150 years) shows its labile behavior. Smooth-curve hydrographs based on estimates of lake level at time scales of decades, centuries, or millennia, such as those presented in previous publications, do not accurately portray the way lake level rises and falls, and a precise plot of post-Bonneville changes in level of Great Salt Lake would resemble the “jagged” historical record. The available sedimentary and geomorphic data are not conducive at this time to the production of a highly precise hydrograph, so we suggest that post-Bonneville lake-level history be portrayed, imprecisely but accurately, as confined generally between the elevation limits of 1285 and 1271 m, with an indication of the exceptional spikes in the lake level.

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USGS2021

Ungaged inflow and loss patterns in urban and agricultural sub‐reaches of the Logan River Observatory

Streams in semi‐arid urban and agricultural environments are often heavily diverted for anthropogenic purposes. However, they simultaneously receive substantial inflows from a variety of ungaged sources including stormwater returns, tile drainage, and irrigation runoff that help sustain flow during dry periods. Due to the inability to identify sources or directly gage many of these inflows, there is a clear need for methods to understand source origination while quantifying potential gains and losses over highly impacted reaches. In the context of the Logan River Observatory, historical gage data illustrate the importance of ungaged and unidentified inflows on maintaining or enhancing flows in both urban and agricultural reaches containing large diversions. To understand the inflows in this portion of the Logan River, we first analysed water samples for ions collected from a subset of representative inflow sources and applied clustering analyses to establish inflow source classifications and associated ion concentration ranges. These representative concentration ranges, combined with mainstem flow and river ion samples taken at sub‐reach scales, allow for the application of flow and mass balances to quantify inflow rates from different sources as well as any losses. These calculations demonstrate significant gains and losses occurring in many sub‐reaches during three sampling events. The dominant land use (urban or agriculture) and flow regime at the time of sampling were the primary drivers of gains and losses. These exchanges were found to be most important below large diversions during low flow conditions. This highlights the need to classify inflow sources (urban or agriculture, surface or groundwater) and estimate their contributions to anticipate instream consequences of land use and water management decisions. As irrigation and water conveyance practices become more efficient, a portion of these ungaged inflows could be diminished or eliminated, thus further depleting streamflow during dry periods.

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USGS2021

The Traverse Ridge paleoseismic site and ruptures crossing the boundary between the Provo and Salt Lake City segments of the Wasatch fault zone, Utah, United States

How structural segment boundaries modulate earthquake behavior is an important scientific and societal question, especially for the Wasatch fault zone (WFZ) where urban areas lie along multiple fault segments. The extent to which segment boundaries arrest ruptures, host moderate magnitude earthquakes, or transmit ruptures to adjacent fault segments is critical for understanding seismic hazard. To help address this outstanding issue, we conducted a paleoseismic investigation at the Traverse Ridge paleoseismic site (TR site) along the ∼7-km-long Fort Canyon segment boundary, which links the Provo (59 km) and Salt Lake City (40 km) segments of the WFZ. At the TR site, we logged two trenches which were cut across sub-parallel traces of the fault, separated by ∼175 m. Evidence from these exposures leads us to infer that at least 3 to 4 earthquakes have ruptured across the segment boundary in the Holocene. Radiocarbon dating of soil material developed below and above fault scarp colluvial packages and within a filled fissure constrains the age of the events. The most recent event ruptured the southern fault trace between 0.2 and 0.4 ka, the penultimate event ruptured the northern fault trace between 0.6 and 3.4 ka, and two prior events occurred between 1.4 and 6.2 ka (on the southern fault trace) and 7.2 and 8.1 ka (northern fault trace). Colluvial wedge heights of these events ranged from 0.7 to 1.2 m, indicating the segment boundary experiences surface ruptures with more than 1 m of vertical displacement. Given these estimates, we infer that these events were greater than Mw 6.7, with rupture extending across the entire segment boundary and portions of one or both adjacent fault segments. The Holocene recurrence of events at the TR site is lower than the closest paleoseismic sites at the adjacent fault segment endpoints. The contrasts in recurrence rates observed within 15 km of the Fort Canyon fault segment boundary may be explained conceptually by a leaky segment boundary model which permits spillover events, ruptures centered on the segment boundary, and segmented ruptures. The TR site demonstrates the utility of paleoseismology within segment boundaries which, through corroboration of displacement data, can demonstrate rupture connectivity between fault segments and test the validity of rupture models.

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USGS2021

Groundwater management process simulations using an updated version of the three-dimensional numerical model of groundwater flow in northern Utah Valley, Utah County, Utah

Groundwater is a primary source of drinking water in northern Utah County. The groundwater system is recharged mainly from precipitation in the adjacent Wasatch Mountains and infiltration of streamflow. In 2004, groundwater withdrawals were estimated to be roughly 44,500 acre-feet per year. In 2016, groundwater withdrawals were estimated to be greater than 63,400 acre-feet per year. To prepare for anticipated future increases in groundwater withdrawals, local cities identified 16 locations as feasible for managed aquifer recharge. Using an updated version of an existing U.S. Geological Survey groundwater flow model of northern Utah County, the Groundwater-Management Process for MODFLOW-2005 was used to investigate optimal managed aquifer recharge scenarios with the objective of maintaining acceptable reductions in simulated discharge at 12 groundwater discharge areas and flowing wells along Utah Lake. The Groundwater-Management Process is applied to a 50-year (2017–66) projection of groundwater conditions using average recharge conditions and a linear increase of approximately 750 acre-feet per year of municipal groundwater withdrawals. Two sets of discharge constraints were applied. The first scenario constrains discharge to greater than or equal to 80 percent of the 2016 simulated groundwater discharge along Utah Lake. The constraint was met with a total managed aquifer recharge rate of roughly 7,300 acre-feet per year during 2042–56, and 15,600 acre-feet per year during 2057–66. A second scenario constrains discharge to greater than or equal to 90 percent of the 2016 simulated discharge. This constraint can only be met at 8 of the 12 discharge areas along Utah Lake. This required a managed aquifer recharge rate of roughly 10,000 acre-feet per year during 2042–56 and 15,400 acre-feet per year during 2057–66. For both scenarios, the Groundwater-Management Process indicated that all managed aquifer recharge sites need to be used to meet discharges constraints. The discharge constraints were informally defined on the basis of the water rights hierarchy associated with Utah Lake.

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USGS2021

Coseismic fault slip and afterslip associated with the M5.7 March 18, 2020 Magna, Utah, earthquake

The 2020 Magna, Utah, earthquake produced observable crustal deformation over a ∼ 100 km 2 area around the southeast margin of Great Salt Lake, but it did not produce any surface rupture. To obtain a detailed picture of the fault slip, we combine strong motion seismic waveforms with GPS static oﬀsets and Interferometric Synthetic Aperture Radar (InSAR) observations to obtain kinematic and static slip models of the event. We sample the regional seismic waveﬁeld with 3-component records from 68 stations of the University of Utah Seismograph Stations network. We ﬁnd that coseismic slip and afterslip, with predominantly normal slip, distributed on a shallowly west-dipping plane, possibly augmented by afterslip on a steeply northeast-dipping plane, best ﬁts the joint dataset. The west-dipping plane locates near previously inferred sources of interseismic creep at depth. Hence the earthquake may have occurred on the downdip ex-tension of the Wasatch fault and activated further slip (afterslip) at shallow depth east of the hypocenter. This inferred afterslip may have driven the vigorous aftershock activity that was concentrated east of the hypocenter.

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USGS2021

Greenhouse gas emissions from an arid-zone reservoir and their environmental policy significance: Results from existing global models and an exploratory dataset

Reservoirs in arid regions often provide critical water storage but little is known about their greenhouse gas (GHG) footprint. While there is growing appreciation of the role reservoirs play as GHG sources, there is a lack of understanding of GHG emission dynamics from reservoirs in arid regions and implications for environmental policy. Here we present initial GHG emission measurements from Lake Powell, a large water storage reservoir in the desert southwest United States. We report CO 2 -eq emissions from the shallow (< 15 m) littoral regions of the reservoir that are higher than the global average areal emissions from reservoirs (9.4 vs. 5.8 g CO 2 -eq m −2 d −1 ) whereas fluxes from the main reservoir were two orders of magnitude lower (0.09 g CO 2 -eq m −2 d −1 ). We then compared our measurements to modeled CO 2 + CH 4 emissions from the reservoir using four global scale models. Factoring these emissions into hydropower production at Lake Powell yielded low GHG emissions per MWh −1 as compared to fossil-fuel based energy sources. With the exception of one model, the estimated hydropower emissions for Lake Powell ranged from 10−32 kg CO 2 -eq MWh −1 , compared to ∼400−1000 kg CO 2 -eq MWh −1 for natural gas, oil, and coal. We also estimate that reduced littoral habitat under low water levels leads to ∼50% reduction in the CO 2 equivalent emissions per MWh. The sensitivity of GHG emissions to reservoir water levels suggests that the interaction will be an important policy consideration in the design and operation of arid region systems.

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USGS2021

Amateur radio operators help fill earthquake donut holes

If you’ve ever seen tall antennas rising from everyday residences in your community and wondered what they are for, it could be that those homes belong to ham radio enthusiasts who enjoy communicating with each other over the airwaves. In addition to having fun with their radios and finding camaraderie, many ham radio operators are also prepared to help neighbors and authorities communicate during disasters. One such group of radio enthusiasts is poised now to serve yet another important role: They will be contributing to a more robust delivery mechanism for critical seismic intensity reports after major earthquakes through the U.S. Geological Survey’s (USGS) Did You Feel It? (DYFI) system.

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