Post Eruption inflation of the East Pacific Rise at 9°50′ N

Nooner, S. L.; Webb, Spahr C.; Buck, W. Roger; Cormier, Marie-Hélène

doi:10.1002/2014gc005389

Cited by 10 publications

(4 citation statements)

References 66 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This magma lens conduit is located near the best‐fit inflation source determined from geodetic data, which corresponds with a near‐vertical pipe‐like body (Hefner et al., 2020; Nooner & Chadwick, 2016), and active magma replenishment via porous flow is inferred to be occurring within this region. The only other site on a MOR where active inflation has been documented to date is on the northern EPR where geodetic observations indicate an inflation source centered at 9°51′N that is located below the AML (Nooner et al., 2014). Magma lenses beneath the AML are detected in the area of this sub‐AML inflation source (Marjanović et al., 2014, 2018), where inflation rates measured over a 3‐year period are greater than expected given regional spreading rates, indicating enhanced magma replenishment at present.…”

Section: Discussionmentioning

confidence: 99%

Stacked Magma Lenses Beneath Mid‐Ocean Ridges: Insights From New Seismic Observations and Synthesis With Prior Geophysical and Geologic Findings

et al. 2021

View full text Add to dashboard Cite

Recent multi‐channel seismic studies of fast spreading and hot‐spot influenced mid‐ocean ridges reveal magma bodies located beneath the mid‐crustal Axial Magma Lens (AML), embedded within the underlying crustal mush zone. We here present new seismic images from the Juan de Fuca Ridge that show reflections interpreted to be from vertically stacked magma lenses in a number of locations beneath this intermediate‐spreading ridge. The brightest reflections are beneath Northern Symmetric segment, from ∼46°42′‐52′N and Split Seamount, where a small magma body at local Moho depths is also detected, inferred to be a source reservoir for the stacked magma lenses in the crust above. The imaged magma bodies are sub‐horizontal, extend continuously for along‐axis lengths of ∼1–8 km, with the shallowest located at depths of ∼100–1,200 m below the AML, and are similar to sub‐AML bodies found at the East Pacific Rise. At both ridges, stacked sill‐like lenses are detected beneath only a small fraction of the ridge length examined and are inferred to mark local sites of higher melt flux and active replenishment from depth. The imaged magma lenses are focused in the upper part of the lower crust, which coincides with the most melt rich part of the crystal mush zone detected in other geophysical studies and where sub‐vertical fabrics are observed in geologic exposures of oceanic crust. We infer that the multi‐level magma accumulations are ephemeral and may result from porous flow and mush compaction, and that they can be tapped and drained during dike intrusion and eruption events.

show abstract

Section: Discussionmentioning

confidence: 99%

Stacked Magma Lenses Beneath Mid‐Ocean Ridges: Insights From New Seismic Observations and Synthesis With Prior Geophysical and Geologic Findings

et al. 2021

View full text Add to dashboard Cite

show abstract

“…After the majority of the extensional stresses built up were released through the plate‐spreading event, the site at the EPR would have started going back to its ambient state of background stress. During the post‐eruption year (deployment 4), the site would have experienced a number of different, competing stresses, which include crustal relaxation following the spreading event, intense hydrothermal cooling of the recent dike intrusion, gradual resumption of extensional stresses, and likely reinflation of the AMC [ Nooner et al ., ]. Correlations with the true fortnightly tides, as well as the upper and lower bound of the modulations, have all regained strong magnitudes and it is difficult to pick out a single dominating force.…”

Section: Discussionmentioning

confidence: 99%

Influence of fortnightly tides on earthquake triggering at the East Pacific Rise at 9°50′N

2016

View full text Add to dashboard Cite

The study of tidal forcing provides an opportunity to view the response of the solid Earth to known changes in stress. Earthquakes triggered by diurnal and semidiurnal tidal forces have been well documented for the deep ocean and some terrestrial environments. However, few studies examine the influence of fortnightly tides on earthquake triggering and only in terrestrial environments. We assess triggering of microearthquakes related to true fortnightly tides and fortnightly tidal modulations along the East Pacific Rise at 9°50′N, where strong diurnal and semidiurnal triggering of earthquakes has been observed. An ocean bottom seismograph experiment collected microearthquake data between October 2003 and January 2007, a time period that included a well‐documented submarine eruption culminating in January 2006. We examine how triggering changed through the build up to and aftermath of this seafloor‐spreading event. Results show that earthquakes occur preferentially during times of increasing peak volumetric stress leading up to the eruption, with strong statistical significance (Schuster Test p values up to 2.22e−31). However, the correlation loses its strength immediately prior to and during the eruptive period (p value as high as 0.2837), when competing tectonic and magmatic stresses may occur. Post‐eruption triggering reappears (p value 1.45e−26) but with opposite phase. Statistical significance is also explored using Monte Carlo method, highlighting limitations of swarm‐dominated time series for the Schuster Test. Nevertheless, the observations are consistent with a shift in the dominating stress triggering the earthquakes from extensional tectonics to magmatic processes, followed by a post‐eruption period of cooling, relaxation, and possibly magma chamber refilling.

show abstract

“…• 51.2 N the on-bottom geodesy study of Nooner et al (2014) provided evidence for inflation of the seafloor of up to 12 cm from 2009 December to 2011 October, corresponding to a source at 2.7 km depth beneath the ridge axis, within this discontinuity region. The other exception is the AML discontinuity centred at 9…”

Section: Segments Located North and South Of The 2005-2006 Lava Flowmentioning

confidence: 95%

Distribution of melt along the East Pacific Rise from 9°30′ to 10°N from an amplitude variation with angle of incidence (AVA) technique

et al. 2015

View full text Add to dashboard Cite

S U M M A R YWe examine along-axis variations in melt content of the axial magma lens (AML) beneath the fast-spreading East Pacific Rise (EPR) using an amplitude variation with angle of incidence (AVA) crossplotting method applied to multichannel seismic data acquired in 2008. The AVA crossplotting method, which has been developed for and, so far, applied for hydrocarbon prospection in sediments, is for the first time applied to a hardrock environment. We focus our analysis on 2-D data collected along the EPR axis from 9• 29.8 N to 9• 58.4 N, a region which encompasses the sites of two well-documented submarine volcanic eruptions (1991-1992 and 2005-2006). AVA crossplotting is performed for a ∼53 km length of the EPR spanning nine individual AML segments (ranging in length from ∼3.2 to 8.5 km) previously identified from the geometry of the AML and disruptions in continuity. Our detailed analyses conducted at 62.5 m interval show that within most of the analysed segments melt content varies at spatial scales much smaller (a few hundred of metres) than the length of the fine-scale AML segments, suggesting high heterogeneity in melt concentration. At the time of our survey, about 2 yr after the eruption, our results indicate that the three AML segments that directly underlie the 2005-2006 lava flow are on average mostly molten. However, detailed analysis at finer-scale intervals for these three segments reveals AML pockets (from >62.5 to 812.5 m long) with a low melt fraction. The longest such mushy section is centred beneath the main eruption site at ∼9• 50.4 N, possibly reflecting a region of primary melt drainage during the 2005-2006 event. The complex geometry of fluid flow pathways within the crust above the AML and the different response times of fluid flow and venting to eruption and magma reservoir replenishment may contribute to the poor spatial correlation between incidence of hydrothermal vents and presence of highly molten AML. The presented results are an important step forward in our ability to resolve small-scale characteristics of the AML and recommend the AVA crossplotting as a tool for examining mid-ocean ridge magma-systems elsewhere.

show abstract

Post Eruption inflation of the East Pacific Rise at 9°50′ N

Cited by 10 publications

References 66 publications

Stacked Magma Lenses Beneath Mid‐Ocean Ridges: Insights From New Seismic Observations and Synthesis With Prior Geophysical and Geologic Findings

Stacked Magma Lenses Beneath Mid‐Ocean Ridges: Insights From New Seismic Observations and Synthesis With Prior Geophysical and Geologic Findings

Influence of fortnightly tides on earthquake triggering at the East Pacific Rise at 9°50′N

Distribution of melt along the East Pacific Rise from 9°30′ to 10°N from an amplitude variation with angle of incidence (AVA) technique

Contact Info

Product

Resources

About