skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Comment to Shreve and Delgado (2023)—“ Trapdoor Fault Activation : A Step Toward Caldera Collapse at Sierra Negra , Galapagos , Ecuador ”
Abstract In their article entitled “Trapdoor Fault Activation:A Step Toward Caldera Collapse at Sierra Negra,Galapagos,Ecuador” Shreve and Delgado (2023,https://doi.org/10.1029/2023jb026437) examine co‐eruptive deformation during the 2018 eruption of Sierra Negra Volcano. One of their major conclusions is that the 2018 eruption, and specifically co‐eruptive faulting, represents the initial stages of caldera collapse. They reach this conclusion because they focus their analysis solely on co‐eruptive deformation, and do not investigate the total (net) deformation for the 2005 to 2018 eruption cycle. Bell, La Famina, et al. (2021,https://doi.org/10.1038/s41467‐021‐21596‐4) investigated both the pre‐ and co‐eruptive phases of the 2018 eruption and showed that net deformation was one of caldera resurgence, not subsidence. In this comment, we demonstrate that the conclusion of collapse, or even initiation of collapse, is attributable to not accounting for pre‐eruptive deformation on the intra‐caldera Trapdoor Fault system and incorrectly assuming that the volcano‐tectonic dynamics of Sierra Negra mimic those of other basaltic calderas.  more » « less
Award ID(s):
2122745 1752477
PAR ID:
10648592
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Journal of Geophysical Research: Solid Earth
Volume:
130
Issue:
10
ISSN:
2169-9313
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Abstract Axial Seamount is an active submarine volcano located at the intersection of the Cobb hot spot and the Juan de Fuca Ridge (45°57′N, 130°01′W). Bottom pressure recorders captured co‐eruption subsidence of 2.4–3.2 m in 1998, 2011, and 2015, and campaign‐style pressure surveys every 1–2 years have provided a long‐term time series of inter‐eruption re‐inflation. The 2015 eruption occurred shortly after the Ocean Observatories Initiative (OOI) Cabled Array came online providing real‐time seismic and deformation observations for the first time. Nooner and Chadwick (2016,https://doi.org/10.1126/science.aah4666) used the available vertical deformation data to model the 2015 eruption deformation source as a steeply dipping prolate‐spheroid, approximating a high‐melt zone or conduit beneath the eastern caldera wall. More recently, Levy et al. (2018,https://doi.org/10.1130/G39978.1) used OOI seismic data to estimate dip‐slip motion along a pair of outward‐dipping caldera ring faults. This fault motion complicates the deformation field by contributing up to several centimeters of vertical seafloor motion. In this study, fault‐induced surface deformation was calculated from the slip estimates of Levy et al. (2018,https://doi.org/10.1130/G39978.1) then removed from vertical deformation data prior to model inversions. Removing fault motion resulted in an improved model fit with a new best‐fitting deformation source located 2.11 km S64°W of the source of Nooner and Chadwick (2016,https://doi.org/10.1126/science.aah4666) with similar geometry. This result shows that ring fault motion can have a significant impact on surface deformation, and future modeling efforts need to consider the contribution of fault motion when estimating the location and geometry of subsurface magma movement at Axial Seamount. 
    more » « less
  2. Abstract The 2018 eruption of Sierra Negra volcano, Galápagos, Ecuador has provided new insights into the mechanisms of caldera resurgence, subsidence, and fissuring at basaltic shield volcanoes. Here, we integrate local (∼0.4 km) seismo‐acoustic records and regional (∼85 km) infrasound array data to present new observations of the 2018 Sierra Negra eruption with improved time and spatial resolutions. These observations include: air‐to‐ground coupling ∼2 hr before the time of the eruption onset, migration of the infrasound tremor from 22:54 June 26 to 12:31 June 27 UT (all times in UT), and persistent infrasound detections during the weeks between 5 July and 18 August from an area that does not coincide with the previously documented eruptive fissures. We interpret air‐to‐ground coupling as infrasound tremor generated in the nearby fissures before the main eruptive phase started, although ambiguity remains in interpreting a single seismic‐infrasonic sensor pair. The progressive location change of the infrasound tremor agrees with the migration of the eruption down the north flank of Sierra Negra at a rate of ∼0.15 ± 0.04 m/s. The weeks‐long persistent detections coincide with a region that has thermal anomalies, co‐eruptive deformation, lava fields, and geological features that could be interpreted as multiple lava tube skylights. Our observations and interpretations provide constraints on the mechanisms underlying fissure formation and magma emplacement at Sierra Negra. 
    more » « less
  3. Abstract The polarFregion ionosphere frequently exhibits sporadic variability (e.g., Meek, 1949,https://doi.org/10.1029/JZ054i004p00339; Hill, 1963,https://doi.org/10.1175/1520‐0469(1963)020<0492:SEOLII>2.0.CO;2). Recent satellite data analysis (Noja et al., 2013,https://doi.org/10.1002/rds.20033; Chartier et al., 2018,https://doi.org/10.1002/2017JA024811) showed that the high‐latitudeFregion ionosphere exhibits sporadic enhancements more frequently in January than in July in both the northern and southern hemispheres. The same pattern has been seen in statistics of the degradation and total loss of GPS service onboard low‐Earth orbit satellites (Xiong et al. 2018,https://doi.org/10.5194/angeo‐36‐679‐2018). Here, we confirm the existence of this annual pattern using ground GPS‐based images of TEC from the MIDAS algorithm. Images covering January and July 2014 confirm that the high‐latitude (>70 MLAT)Fregion exhibits a substantially larger range of values in January than in July in both the northern and southern hemispheres. The range of TEC values observed in the polar caps is 38–57 TECU (north‐south) in January versus 25–37 TECU in July. First‐principle modeling using SAMI3 reproduces this pattern, and indicates that it is caused by an asymmetry in plasma levels (30% higher in January than in July across both polar caps), as well as 17% longer O+plasma lifetimes in northern hemisphere winter, compared to southern hemisphere winter. 
    more » « less
  4. Abstract Liu et al. (2022,https://doi.org/10.1029/2021GL093691) used Rayleigh waves extracted from the cross‐correlation of ambient noise recorded by two stations to monitor the seismic velocity variations associated with the 2018 Kı̄lauea eruption. However, their study ignored the fact that the tremors on the Island of Hawai'i were dominated by a source at the Kı̄lauea summit before the eruption. Close inspection of the waveforms of the station pair PAUD‐STCD shows a simple, mistakenly identified wave traveling direction in Liu et al. (2022,https://doi.org/10.1029/2021GL093691). A correct wave traveling direction agrees with the noise source model, where the dominant tremor source should be at the Kı̄lauea summit. Because of the drastic change in the tremor source after the eruption, the cross‐correlation of the tremor records may reflect predominantly changes in the source rather than in the medium properties between the two stations. 
    more » « less
  5. Abstract Wave breaking induced bubbles contribute a significant part of air‐sea gas fluxes. Recent modeling of the sea state dependent CO2flux found that bubbles contribute up to ∼40% of the total CO2air‐sea fluxes (Reichl & Deike, 2020,https://doi.org/10.1029/2020gl087267). In this study, we implement the sea state dependent bubble gas transfer formulation of Deike and Melville (2018,https://doi.org/10.1029/2018gl078758) into a spectral wave model (WAVEWATCH III) incorporating the spectral modeling of the wave breaking distribution from Romero (2019,https://doi.org/10.1029/2019gl083408). We evaluate the accuracy of the sea state dependent gas transfer parameterization against available measurements of CO2gas transfer velocity from 9 data sets (11 research cruises, see Yang et al. (2022,https://doi.org/10.3389/fmars.2022.826421)). The sea state dependent parameterization for CO2gas transfer velocity is consistent with observations, while the traditional wind‐only parameterization used in most global models slightly underestimates the observations of gas transfer velocity. We produce a climatology of the sea state dependent gas transfer velocity using reanalysis wind and wave data spanning 1980–2017. The climatology shows that the enhanced gas transfer velocity occurs frequently in regions with developed sea states (with strong wave breaking and high significant wave height). The present study provides a general sea state dependent parameterization for gas transfer, which can be implemented in global coupled models. 
    more » « less