Mammoth Mountain Research Articles

Bacterial community in ancient permafrost alluvium at the Mammoth Mountain (Eastern Siberia)

Permanently frozen (approx. 3.5Ma) alluvial Neogene sediments exposed in the Aldan river valley at the Mammoth Mountain (Eastern Siberia) are unique, ancient, and poorly studied permafrost environments. So far, the structure of the indigenous bacterial community has remained unknown. Use of 16S metagenomic analysis with total DNA isolation using DNA Spin Kit for Soil (MO-Bio) and QIAamp DNA Stool Mini Kit (Qiagen) has revealed the major and minor bacterial lineages in the permafrost alluvium sediments. In sum, 61 Operational Taxonomic Units (OTUs) with 31,239 reads (Qiagen kit) and 15,404 reads (Mo-Bio kit) could be assigned to the known taxa. Only three phyla, Bacteroidetes, Proteobacteria and Firmicutes, comprised >5% of the OTUs abundance and accounted for 99% of the total reads. OTUs pertaining to the top families (Chitinophagaceae, Caulobacteraceae, Sphingomonadaceae, Bradyrhizobiaceae, Halomonadaceae) held >90% of reads. The abundance of Actinobacteria was less (0.7%), whereas members of other phyla (Deinococcus-Thermus, Cyanobacteria/Chloroplast, Fusobacteria, and Acidobacteria) constituted a minor fraction of reads. The bacterial community in the studied ancient alluvium differs from other permafrost sediments, mainly by predominance of Bacteroidetes (>52%). The diversity of this preserved bacterial community has the potential to cause effects unknown if prompted to thaw and spread with changing climate. Therefore, this study elicits further reason to study how reintroduction of these ancient bacteria could affect the surrounding ecosystem, including current bacterial species.

Fluid-driven uplift at Long Valley Caldera, California: Geologic perspectives

Since persistent seismicity began in the Sierra Nevada adjacent to Long Valley caldera in 1978–1980, intracaldera unrest has been marked by (1) episodes of uplift totaling ~83cm, centered on the middle Pleistocene resurgent dome, and (2) recurrent earthquake swarms along a 12-km-long segment of the caldera's ring-fault zone that is contiguous with both the dome and the Sierran seismogenic domain. Others have attributed the recent unrest to magmatic intrusion(s), but it is argued here that evidence for new magma is lacking and that ongoing uplift and ring-fault-zone seismicity are both promoted by ascent of aqueous fluid released by second boiling of the residue of the enormous Pleistocene rhyolitic reservoir terminally crystallizing at depths ≥10km. For 2Myr, eruptive vent clusters migrated southwestward from Glass Mountain to Mammoth Mountain. There has been no eruption on the resurgent dome since 500ka, and since 230ka volcanism has been restricted to the caldera's west moat and contiguous Sierran terrain, both outside the structural caldera. High-temperature hydrothermal activity in the central caldera waned after ~300ka, cooling the Pleistocene rhyolitic focus to the extent that drilling on the resurgent dome found mid-caldera temperature to be only 100°C and isothermal at depths of 2–3km. Beneath most of the resurgent dome, there is little seismicity at any depth, no emission of magmatic CO2 or other magmatic gases, no elevated 3He/4He ratios, and only normal to below-normal heat flow. Most of the 75-km-long ring-fault zone is likewise aseismic, excepting only the 12-km segment contiguous with the extracaldera seismogenic domain in the Sierra. Since 1980, the Sierran seismicity has released 3.6 times more cumulative seismic energy than have intracaldera earthquakes. The caldera seismicity is not driven by stresses associated with the adjacent uplift but, instead, by the extracaldera tectonic stressfield. Sierran seismicity activated the directly contiguous south-moat segment of the ring-fault zone, which had originated in the caldera-forming eruption at 767ka and everywhere else remains sealed. Hypocenter relocation studies of 1000s of earthquakes along the seismic segment have resolved recurrent upward-migrating swarms within networks of cryptic faults, apparently triggered by rapidly ascending pulses of high-pressure low-viscosity aqueous fluid. Entering the brittle crust at depths of 8–10km, such fluid is just what should be expected from second boiling of the late-stage CO2-poor rhyolitic residue. The fluid provides the pressure source above the apex of the crystallizing caldera-wide pluton and then escapes laterally to the newly reactivated southern segment of the ring-fault zone, its only available permeable pathway, where it mediates the ongoing south-moat seismicity.

Ancient permafrost staphylococci carry antibiotic resistance genes.

ABSTRACTBackground: Permafrost preserves a variety of viable ancient microorganisms. Some of them can be cultivated after being kept at subzero temperatures for thousands or even millions of years.Objective: To cultivate bacterial strains from permafrost.Design: We isolated and cultivated two bacterial strains from permafrost that was obtained at Mammoth Mountain in Siberia and attributed to the Middle Miocene. Bacterial genomic DNA was sequenced with 40–60× coverage and high-quality contigs were assembled. The first strain was assigned to Staphylococcus warneri species (designated MMP1) and the second one to Staphylococcus hominis species (designated MMP2), based on the classification of 16S ribosomal RNA genes and genomic sequences.Results: Genomic sequence analysis revealed the close relation of the isolated ancient bacteria to the modern bacteria of this species. Moreover, several genes associated with resistance to different groups of antibiotics were found in the S. hominis MMP2 genome.Conclusions: These findings supports a hypothesis that antibiotic resistance has an ancient origin. The enrichment of cultivated bacterial communities with ancient permafrost strains is essential for the analysis of bacterial evolution and antibiotic resistance.

Phylogenetic analysis of microorganisms from permafrost

Microbiological analysis of samples from the permafrost of Mammoth Mountain (Republic of Sakha (Yakutia)) was performed. Gram-positive bacteria of the genus Bacillus were isolated. DNA of the isolated microorganisms was extracted and their genomes were sequenced. Phylogenetic analysis of the microorganisms from the permafrost was performed.

Phylogenetic analysis of microorganisms from permafrost

From the permafrost of Mammoth Mountain in the Republic of Saha (Yakutia) samples were obtained for subsequent microbiological analysis. We were isolated Gram-positive bacterium Bacillus genus. Conducted DNA isolation and sequencing of the isolated bacteria. Phylogenetic analysis of the microorganisms from the permafrost.

Three‐dimensional electrical resistivity model of the hydrothermal system in Long Valley Caldera, California, from magnetotellurics

AbstractThough shallow flow of hydrothermal fluids in Long Valley Caldera, California, has been well studied, neither the hydrothermal source reservoir nor heat source has been well characterized. Here a grid of magnetotelluric data were collected around the Long Valley volcanic system and modeled in 3‐D. The preferred electrical resistivity model suggests that the source reservoir is a narrow east‐west elongated body 4 km below the west moat. The heat source could be a zone of 2–5% partial melt 8 km below Deer Mountain. Additionally, a collection of hypersaline fluids, not connected to the shallow hydrothermal system, is found 3 km below the medial graben, which could originate from a zone of 5–10% partial melt 8 km below the south moat. Below Mammoth Mountain is a 3 km thick isolated body containing fluids and gases originating from an 8 km deep zone of 5–10% basaltic partial melt.

An efficient repeating signal detector to investigate earthquake swarms

AbstractRepetitive earthquake swarms have been recognized as key signatures in fluid injection induced seismicity, precursors to volcanic eruptions, and slow slip events preceding megathrust earthquakes. We investigate earthquake swarms by developing a Repeating Signal Detector (RSD), a computationally efficient algorithm utilizing agglomerative clustering to identify similar waveforms buried in years of seismic recordings using a single seismometer. Instead of relying on existing earthquake catalogs of larger earthquakes, RSD identifies characteristic repetitive waveforms by rapidly identifying signals of interest above a low signal‐to‐noise ratio and then grouping based on spectral and time domain characteristics, resulting in dramatically shorter processing time than more exhaustive autocorrelation approaches. We investigate seismicity in four regions using RSD: (1) volcanic seismicity at Mammoth Mountain, California, (2) subduction‐related seismicity in Oaxaca, Mexico, (3) induced seismicity in Central Alberta, Canada, and (4) induced seismicity in Harrison County, Ohio. In each case, RSD detects a similar or larger number of earthquakes than existing catalogs created using more time intensive methods. In Harrison County, RSD identifies 18 seismic sequences that correlate temporally and spatially to separate hydraulic fracturing operations, 15 of which were previously unreported. RSD utilizes a single seismometer for earthquake detection which enables seismicity to be quickly identified in poorly instrumented regions at the expense of relying on another method to locate the new detections. Due to the smaller computation overhead and success at distances up to ~50 km, RSD is well suited for real‐time detection of low‐magnitude earthquake swarms with permanent regional networks.

Massive Carbon Dioxide Stores Beneath Mammoth Mountain

Gas in rocky pores beneath the surface of California's Mammoth Mountain could fuel dangerous carbon dioxide emissions for the next 28 to 1100 years.

Tomographic image of a seismically active volcano: Mammoth Mountain, California

AbstractHigh‐resolution tomographic P wave, S wave, and VP/VS velocity structure models are derived for Mammoth Mountain, California, using phase data from the Northern California Seismic Network and a temporary deployment of broadband seismometers. An anomalous volume (5.1 × 109 to 5.9 × 1010m3) of low P and low S wave velocities is imaged beneath Mammoth Mountain, extending from near the surface to a depth of ∼2 km below sea level. We infer that the reduction in seismic wave velocities is due to the presence of CO2 distributed in oblate spheroid pores with mean aspect ratio α = 1.6 × 10−3 to 7.9 × 10−3 (crack‐like pores) and mean gas volume fraction ϕ = 8.1 × 10−4 to 3.4 × 10−3. The pore density parameter κ = 3ϕ/(4πα) = na3=0.11, where n is the number of pores per cubic meter and a is the mean pore equatorial radius. The total mass of CO2 is estimated to be 4.6 × 109 to 1.9 × 1011 kg. The local geological structure indicates that the CO2 contained in the pores is delivered to the surface through fractures controlled by faults and remnant foliation of the bedrock beneath Mammoth Mountain. The total volume of CO2 contained in the reservoir suggests that given an emission rate of 500 tons day−1, the reservoir could supply the emission of CO2 for ∼25–1040 years before depletion. Continued supply of CO2 from an underlying magmatic system would significantly prolong the existence of the reservoir.

CUES—a study site for measuring snowpack energy balance in the Sierra Nevada

Accurate measurement and modeling of the snowpack energy balance are critical to understanding the terrestrial water cycle. Most of the water resources in the western US come from snowmelt, yet statistical runoff models that rely on the historical record are becoming less reliable because of a changing climate. For physically based snow melt models that do not depend on past conditions, ground based measurements of the energy balance components are imperative for verification. For this purpose, the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory (CRREL) and the University of California, Santa Barbara (UCSB) established the “CUES” snow study site (CRREL/UCSB Energy Site, http://www.snow.ucsb.edu/) at 2940 m elevation on Mammoth Mountain, California. We describe CUES, provide an overview of research, share our experience with scientific measurements, and encourage future collaborative research. Snow measurements began near the current CUES site for ski area operations in 1969. In the 1970s, researchers began taking scientific measurements. Today, CUES benefits from year round gondola access and a fiber optic internet connection. Data loggers and computers automatically record and store over 100 measurements from more than 50 instruments each minute. CUES is one of only five high altitude mountain sites in the Western US where a full suite of energy balance components are measured. In addition to measuring snow on the ground at multiple locations, extensive radiometric and meteorological measurements are recorded. Some of the more novel measurements include scans by an automated terrestrial LiDAR, passive and active microwave imaging of snow stratigraphy, microscopic imaging of snow grains, snowflake imaging with a multi-angle camera, fluxes from upward and downward looking radiometers, snow water equivalent from different types of snow pillows, snowmelt from lysimeters, and concentration of impurities in the snowpack. We give an example of terrain-corrected snow albedo measurements compared to several models and of sublimation measured from lysimeter and snow pillow melt. We conclude with some thoughts on the future of CUES.

Integrated thermal infrared imaging and structure-from-motion photogrammetry to map apparent temperature and radiant hydrothermal heat flux at Mammoth Mountain, CA, USA

This work presents a method to create high-resolution (cm-scale) orthorectified and georeferenced maps of apparent surface temperature and radiant hydrothermal heat flux and estimate the radiant hydrothermal heat emission rate from a study area. A ground-based thermal infrared (TIR) camera was used to collect (1) a set of overlapping and offset visible imagery around the study area during the daytime and (2) time series of co-located visible and TIR imagery at one or more sites within the study area from pre-dawn to daytime. Daytime visible imagery was processed using the structure-from-motion photogrammetric method to create a digital elevation model onto which pre-dawn TIR imagery was orthorectified and georeferenced. Three-dimensional maps of apparent surface temperature and radiant hydrothermal heat flux were then visualized and analyzed from various computer platforms (e.g., Google Earth, ArcGIS). We demonstrate this method at the Mammoth Mountain fumarole area on Mammoth Mountain, CA. Time-averaged apparent surface temperatures and radiant hydrothermal heat fluxes were observed up to 73.7°C and 450Wm−2, respectively, while the estimated radiant hydrothermal heat emission rate from the area was 1.54kW. Results should provide a basis for monitoring potential volcanic unrest and mitigating hydrothermal heat-related hazards on the volcano.

Fluid‐faulting interactions: Fracture‐mesh and fault‐valve behavior in the February 2014 Mammoth Mountain, California, earthquake swarm

AbstractFaulting and fluid transport in the subsurface are highly coupled processes, which may manifest seismically as earthquake swarms. A swarm in February 2014 beneath densely monitored Mammoth Mountain, California, provides an opportunity to witness these interactions in high resolution. Toward this goal, we employ massive waveform‐correlation‐based event detection and relative relocation, which quadruples the swarm catalog to more than 6000 earthquakes and produces high‐precision locations even for very small events. The swarm's main seismic zone forms a distributed fracture mesh, with individual faults activated in short earthquake bursts. The largest event of the sequence,M3.1, apparently acted as a fault valve and was followed by a distinct wave of earthquakes propagating ~1 km westward from the updip edge of rupture, 1–2 h later. Late in the swarm, multiple small, shallower subsidiary faults activated with pronounced hypocenter migration, suggesting that a broader fluid pressure pulse propagated through the subsurface.

Structural controls on the emission of magmatic carbon dioxide gas, Long Valley Caldera, USA

AbstractWe present a degassing study of Long Valley Caldera that explores the structural controls upon emissions of magmatic carbon dioxide gas. A total of 223 soil gas samples were collected and analyzed for stable carbon isotopes using a field‐portable cavity ring‐down spectrometer. This novel technique is flexible, accurate, and provides sampling feedback on a daily basis. Sampling sites included major and minor volcanic centers, regional throughgoing faults, caldera‐related structures, zones of elevated seismicity, and zones of past and present hydrothermal activity. The classification of soil gases based on their δ13C and CO2 values reveals a mixing relationship among three end‐members: atmospheric, biogenic, and magmatic. Signatures dominated by biogenic contributions (~4 vol %, −24‰) are found on the caldera floor, the interior of the resurgent dome, and areas associated with the Hilton Creek and Hartley Springs fault systems. With the introduction of the magmatic component (~100 vol %, −4.5‰), samples acquire mixing and hydrothermal signatures and are spatially associated with the central caldera and Mammoth Mountain. In particular, they are concentrated along the southern margin of the resurgent dome where the interplay between resurgence‐related reverse faulting and a bend in the regional fault system has created a highly permeable fracture network, suitable for the formation of shallow hydrothermal systems. This contrasts with the south moat, where despite elevated seismicity, a thick sedimentary cover has formed an impermeable cap, inhibiting the ascent of fluids and gases to the surface.

Magmatic gas emissions at Holocene volcanic features near Mono Lake, California, and their relation to regional magmatism

Silicic lavas have erupted repeatedly in the Mono Basin over the past few thousand years, forming the massive domes and coulees of the Mono Craters chain and the smaller island vents in Mono Lake. We report here on the first systematic study of magmatic CO2 emissions from these features, conducted during 2007–2010. Most notably, a known locus of weak steam venting on the summit of North Coulee is actually enclosed in a large area (~0.25km2) of diffuse gas discharge that emits 10–14t/d of CO2, mostly at ambient temperature. Subsurface gases sampled here are heavily air-contaminated, but after standard corrections are applied, show average δ13C-CO2 of −4.72‰, 3He/4He of 5.89RA, and CO2/3He of 0.77×1010, very similar to the values in fumarolic gas from Mammoth Mountain and the Long Valley Caldera immediately to the south of the basin. If these values also characterize the magmatic gas source at Mono Lake, where CO2 is captured by the alkaline lake water, a magmatic CO2 upflow beneath the lake of ~4t/d can be inferred. Groundwater discharge from the Mono Craters area transports ~13t/d of 14C-dead CO2 as free gas and dissolved carbonate species, and adding in this component brings the estimated total magmatic CO2 output to 29t/d for the two silicic systems in the Mono Basin. If these emissions reflect intrusion and degassing of underlying basalt with 0.5wt.% CO2, a modest intrusion rate of 0.00075km3/yr is indicated. Much higher intrusion rates are required to account for CO2 emissions from Mammoth Mountain and the West Moat of the Long Valley Caldera.

Mammoth Mountain and its mafic periphery--A late Quaternary volcanic field in eastern California

The trachydacite complex of Mammoth Mountain and an array of contemporaneous mafic volcanoes in its periphery together form a discrete late Pleistocene magmatic system that is thermally and compositionally independent of the adjacent subalkaline Long Valley system (California, USA). The Mammoth system first erupted ca. 230 ka, last erupted ca. 8 ka, and remains restless and potentially active. Magmas of the Mammoth system extruded through Mesozoic plutonic rocks of the Sierra Nevada batholith and extensive remnants of its prebatholith wall rocks. All of the many mafic and silicic vents of the Mammoth system are west or southwest of the structural boundary of Long Valley caldera; none is inboard of the caldera’s buried ring-fault zone, and only one Mammoth-related vent is within the zone. Mammoth Mountain has sometimes been called part of the Inyo volcanic chain, an ascription we regard inappropriate and misleading. The scattered vent array of the Mammoth system, 10 × 20 km wide, is unrelated to the range-front fault zone, and its broad nonlinear footprint ignores both Long Valley caldera and the younger Mono-Inyo range-front vent alignment. Moreover, the Mammoth Mountain dome complex (63%–71% SiO 2 ; 8.0%–10.5% alkalies) ended its period of eruptive activity (100–50 ka) long before Holocene inception of Inyo volcanism. Here we describe 25 silicic eruptive units that built Mammoth Mountain and 37 peripheral units, which include 13 basalts, 15 mafic andesites, 6 andesites, and 3 dacites. Chemical data are appended for nearly 900 samples, as are paleomagnetic data for ∼150 sites drilled. The 40 Ar/ 39 Ar dates (230–16 ka) are given for most units, and all exposed units are younger than ca. 190 ka. Nearly all are mildly alkaline, in contrast to the voluminous subalkaline rhyolites of the contiguous long-lived Long Valley magma system. Glaciated remnants of Neogene mafic and trachydacitic lavas (9.1–2.6 Ma) are scattered near Mammoth Mountain, but Quaternary equivalents older than ca. 230 ka are absent. The wide area of late Quaternary Mammoth magmatism remained amagmatic during the long interval (2.2–0.3 Ma) of nearby Long Valley rhyolitic eruptions.

Decadal-scale variability of diffuse CO2 emissions and seismicity revealed from long-term monitoring (1995–2013) at Mammoth Mountain, California, USA

Mammoth Mountain, California, is a dacitic volcano that has experienced several periods of unrest since 1989. The onset of diffuse soil CO2 emissions at numerous locations on the flanks of the volcano began in 1989–1990 following an 11-month period of heightened seismicity. CO2 emission rates were measured yearly from 1995 to 2013 at Horseshoe Lake (HSL), the largest tree kill area on Mammoth Mountain, and measured intermittently at four smaller degassing areas around Mammoth from 2006 to 2013. The long-term record at HSL shows decadal-scale variations in CO2 emissions with two peaks in 2000–2001 and 2011–2012, both of which follow peaks in seismicity by 2–3years. Between 2000 and 2004 emissions gradually declined during a seismically quiet period, and from 2004 to 2009 were steady at ~100metric tonnes per day (td−1). CO2 emissions at the four smaller tree-kill areas also increased by factors of 2–3 between 2006 and 2011–2012, demonstrating a mountain-wide increase in degassing. Delays between the peaks in seismicity and degassing have been observed at other volcanic and hydrothermal areas worldwide, and are thought to result from an injection of deep CO2-rich fluid into shallow subsurface reservoirs causing a pressurization event with a delayed transport to the surface. Such processes are consistent with previous studies at Mammoth, and here we highlight (1) the mountain-wide response, (2) the characteristic delay of 2–3years, and (3) the roughly decadal reoccurrence interval for such behavior. Our best estimate of total CO2 degassing from Mammoth Mountain was 416td−1 in 2011 during the peak of emissions, over half of which was emitted from HSL. The cumulative release of CO2 between 1995 and 2013 from diffuse emissions is estimated to be ~2–3Mt, and extrapolation back to 1989 gives ~4.8Mt. This amount of CO2 release is similar to that produced by the mid-sized (VEI 3) 2009 eruption of Redoubt Volcano in Alaska (~2.3Mt over 11months), and significantly lower than long-term emissions from hydrothermal areas such as Solfatara in Campi Flegrei, Italy (16Mt over 28years).

Laboratory investigations of weathering of soils from Mammoth Mountain, CA, a naturally CO2-impacted field site.

The potential impacts of CO2 leakage from a natural subsurface reservoir on soil and water quality were studied. Field measurements of soil pore CO2 concentrations and visual inspection of plants at Mammoth Mountain, CA, allowed the demarcation of tree-kill and non-tree-kill zones, with CO2 concentrations >100,000 ppm and ∼ 1,000 ppm, respectively. Soils collected from six sites along a transect stretching from the center of the tree-kill zone to an equidistant point into the non-tree-kill zone were analyzed for surface area and organic carbon content. Batch and column leaching tests were conducted to determine the extent of weathering induced by the presence of CO2 in the aqueous solution. Soils deep into the tree-kill area exhibited significantly higher surface areas (10.67 m(2)/g vs 2.53 m(2)/g) and lower organic carbon content (9,550 mg/kg vs 35,550 mg/kg). Batch results indicated that lower pH values (∼ 2) released higher concentrations of Mg, Si, Fe, and As, while, for soils in the tree-kill zone, longer-term batch results indicated higher releases at the higher pH of 5.5. Column experiments were used to compare the effects of pH adjusted using HCl vs CO2. For pore volumes (PV) < 100, CO2 enhanced trace element release. For 100 < PV < 10,000 concentrations of elements in the two systems were equivalent and steady. At PV > 10,000, after a drop in pH in the CO2 system, larger amounts of Fe and As were released, suggesting a CO2-induced dissolution of Fe-silicates/clays and/or reductive dissolution of Fe(3+) that releases Fe-bound arsenic. The specific role of pore water-dissolved CO2 on the release of trace elements is hitherto unknown. However, interactions of pore-water CO2 and the minerals in the Mammoth Mountain soils can cause the release of environmental pollutants.

Multi-scale observations of the variability of magmatic CO2 emissions, Mammoth Mountain, CA, USA

One of the primary indicators of volcanic unrest at Mammoth Mountain is diffuse emission of magmatic CO2, which can effectively track this unrest if its variability in space and time and relationship to near-surface meteorological and hydrologic phenomena versus those occurring at depth beneath the mountain are understood. In June–October 2013, we conducted accumulation chamber soil CO2 flux surveys and made half-hourly CO2 flux measurements with automated eddy covariance and accumulation chamber (auto-chamber) instrumentation at the largest area of diffuse CO2 degassing on Mammoth Mountain (Horseshoe Lake tree kill; HLTK). Estimated CO2 emission rates for HLTK based on 20 June, 30 July, and 24–25 October soil CO2 flux surveys were 165, 172, and 231td−1, respectively. The average (June–October) CO2 emission rate estimated for this area was 123td−1 based on an inversion of 4527 eddy covariance CO2 flux measurements and corresponding modeled source weight functions. Average daily eddy covariance and auto-chamber CO2 fluxes consistently declined over the four-month observation time. Wavelet analysis of auto-chamber CO2 flux and environmental parameter time series was used to evaluate the periodicity of, and local correlation between these variables in time–frequency space. Overall, CO2 emissions at HLTK were highly dynamic, displaying short-term (hourly to weekly) temporal variability related to meteorological and hydrologic changes, as well as long-term (monthly to multi-year) variations related to migration of CO2-rich magmatic fluids beneath the volcano. Accumulation chamber soil CO2 flux surveys were also conducted in the four additional areas of diffuse CO2 degassing on Mammoth Mountain in July–August 2013. Summing CO2 emission rates for all five areas yielded a total for the mountain of 311td−1, which may suggest that emissions returned to 1998–2009 levels, following an increase from 2009 to 2011.

Crustal migration of CO2-rich magmatic fluids recorded by tree-ring radiocarbon and seismicity at Mammoth Mountain, CA, USA

Unrest at Mammoth Mountain over the past several decades, manifest by seismicity, ground deformation, diffuse CO2 emissions, and elevated He3/He4 ratios in fumarolic gases has been driven by the release of CO2-rich fluids from basaltic intrusions in the middle to lower crust. Recent unrest included the occurrence of three lower-crustal (32–19 km depth) seismic swarms beneath Mammoth Mountain in 2006, 2008 and 2009 that were consistently followed by peaks in the occurrence rate of shallow (⩽10 km depth) earthquakes. We measured C14 in the growth rings (1998–2012) of a tree growing in the largest (∼0.3 km2) area of diffuse CO2 emissions on Mammoth Mountain (the Horseshoe Lake tree kill; HLTK) and applied atmospheric CO2 concentration source area modeling to confirm that the tree was a reliable integrator of magmatic CO2 emissions over most of this area. The tree-ring C14 record implied that magmatic CO2 emissions from the HLTK were relatively stable from 1998 to 2009, nearly doubled from 2009 to 2011, and then declined by the 2012 growing season. The initial increase in CO2 emissions was detected during the growing season that immediately followed the largest (February 2010) peak in the occurrence rate of shallow earthquakes. Migration of CO2-rich magmatic fluids may have driven observed patterns of elevated deep, then shallow seismicity, while the relationship between pore fluid pressures within a shallow (upper 3 km of crust) fluid reservoir and permeability structure of the reservoir cap rock may have controlled the temporal pattern of surface CO2 emissions.

Wavelet-based multifractal analysis of earthquakes temporal distribution in Mammoth Mountain volcano, Mono County, Eastern California

This paper presents a wavelet-based multifractal approach to characterize the statistical properties of temporal distribution of the 1982–2012 seismic activity in Mammoth Mountain volcano. The fractal analysis of time-occurrence series of seismicity has been carried out in relation to seismic swarm in association with magmatic intrusion happening beneath the volcano on 4 May 1989. We used the wavelet transform modulus maxima based multifractal formalism to get the multifractal characteristics of seismicity before, during, and after the unrest. The results revealed that the earthquake sequences across the study area show time-scaling features. It is clearly perceived that the multifractal characteristics are not constant in different periods and there are differences among the seismicity sequences. The attributes of singularity spectrum have been utilized to determine the complexity of seismicity for each period. Findings show that the temporal distribution of earthquakes for swarm period was simpler with respect to pre- and post-swarm periods.