Hydroacoustic monitoring of seismicity at the slow‐spreading Mid‐Atlantic Ridge

Smith, Deborah; Tolstoy, M.; Fox, Christopher G.; Bohnenstiehl, D. R.; Matsumoto, Haru; Fowler, Matthew J.

doi:10.1029/2001gl013912

Cited by 92 publications

(87 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The remaining sections of the ridge axis were unclassified. Seismicity data were obtained from the hydrophone catalog 11 and from the NEIC teleseismic catalog (http://neic.usgs.gov/). So as to remove intraplate seismicity and that associated with off-axis deformation, we restricted our analysis to events in oceanic lithosphere younger than 3 Myr, based on the digital seafloor age map 29 .…”

Section: Methods Summarymentioning

confidence: 99%

“…The remaining ~20% of the axis is unclassified owing to limited bathymetric coverage or to unclear morphology at discontinuities and oblique ridge sections (see interpreted maps and Table 1 There is an excellent correlation between mode of accretion and seismicity at the ridge axis. This section of the MAR was hydroacoustically monitored between January 1999 and September 2003 11 . The hydroacoustic catalogue is complementary to the >30 year teleseismic catalogue, as it records smaller magnitude events (magnitude of completeness of 3 and 5, respectively 12 ), over a shorter period of time (<5 vs. >30 years).…”

mentioning

confidence: 99%

See 1 more Smart Citation

Central role of detachment faults in accretion of slow-spreading oceanic lithosphere

Escartı́n

Smith

Cann

et al. 2008

Nature

439

374

View full text Add to dashboard Cite

Enhanced seismicity is probably generated along detachment faults accommodating a sizeable proportion of the total plate separation. In contrast, symmetrical segments have lower levels of seismicity, which concentrates primarily at their ends. Basalts erupted along asymmetrical segments have compositions that are consistent with crystallization at higher pressures than basalts from symmetrical segments, and with lower extents of partial melting of the mantle. The large fields of detachment surfaces recently identified in oceanic crust formed along the slow spreading MAR and ultra-slow spreading South-West Indian Ridge (SWIR) 3,6 demonstrate the involvement of these structures in the accretion of a larger portion of the oceanic lithosphere than previously inferred from seafloor corrugated planes alone 7 . The resulting seafloor morphology and lithospheric structure on the flanks of the ridge axis are strongly asymmetrical 3 and differ from the more regular and roughly symmetrical axis-parallel abyssal hill fabric believed to characterize 'normal' slow-spreading seafloor. The abyssal hill morphology is caused by ridge-parallel, highangle faulting of volcanic seafloor 8 (Figures 1a-c). In contrast, detachment-related terrain is caused by long-lived steep, normal faults initiated beneath the rift valley floor that rotate to low angles as their footwalls are exposed 7,8 . Distinctive narrow ridges with steep outward-facing slopes that are often curved in plan view develop near exposed detachments at the seafloor, and bound deep swales 7 (Figures 1d-e), producing blocky and chaotic terrain 7,9 . The asymmetric nature of accretion in the presence of detachments is also observed in the overall lithospheric structure, composition and geophysical character wherever data are available 3,4,10 . The MAR lacks the broad ridges only found along the melt-poor SWIR, likely a manifestation of detachment faulting that is different from striated fault planes and associated structure 3 . There is an excellent correlation between mode of accretion and seismicity at the ridge axis. This section of the MAR was hydroacoustically monitored between January 1999 and September 2003 11 . The hydroacoustic catalogue is complementary to the >30 year teleseismic catalogue, as it records smaller magnitude events (magnitude of completeness of 3 and 5, respectively 12 ), over a shorter period of time (<5 vs. >30 years). Both seismic catalogues show that detachment-dominated, asymmetrical ridge sections host ~75% more hydroacoustic events and ~65% more teleseismic events than 4 symmetrical segments (Figure 2b and c). The concentration of seismicity at segments shown to have active detachment faults (Figures 1d-e), such as the Logachev massif south of the Fifteen-Twenty Fracture zone and the TAG detachment fault near 26°N 6,7,13 , is thus a general pattern. Active detachments also control the zones of sustained seismicity, which lack shock-aftershock sequences that were previously identified along the northern MAR 14 . Differences between the hyd...

show abstract

Section: Methods Summarymentioning

confidence: 99%

mentioning

confidence: 99%

Central role of detachment faults in accretion of slow-spreading oceanic lithosphere

Escartı́n

Smith

Cann

et al. 2008

Nature

439

374

View full text Add to dashboard Cite

show abstract

“…Between 1999-2005 an autonomous hydrophone array in the North Atlantic 22 recorded the hydroacoustic energy from thousands of earthquakes of smaller magnitude (>2.5). Hydroacoustic events are better located than those detected teleseismically 22,23 , and clearly show the currently active sections of MAR segments 16 . Two sections of ridge between the Fifteen-Twenty and Marathon fracture zones (Fig.…”

mentioning

confidence: 99%

Widespread active detachment faulting and core complex formation near 13° N on the Mid-Atlantic Ridge

Smith

Cann

Escartı́n

2006

Nature

Self Cite

258

266

View full text Add to dashboard Cite

Oceanic core complexes are massifs in which lower crustal and upper mantle rocks are exposed at the sea floor 1-3 . They form at mid-ocean ridges through slip on detachment faults rooted below the spreading axis 2-6 . To date, most studies of core complexes have been based on isolated inactive massifs that have spread away from ridge axes. A new survey of the Mid-Atlantic Ridge (MAR) near 13°N reveals a segment in which a number of linked detachment faults extend for 75 km along one flank of the spreading axis. The detachment faults are apparently all currently active and at various stages of development. A field of extinct core complexes extends away from the axis for at least 100 km. The new data document the topographic characteristics of actively-forming core complexes and their evolution from initiation within the axial valley floor to maturity and eventual inactivity. Within the surrounding region there is a strong correlation between detachment fault morphology at the ridge axis and high rates of hydroacoustically-recorded earthquake seismicity. Preliminary examination of seismicity and seafloor morphology farther north along the MAR suggests that active detachment faulting is occurring in many segments and that detachment faulting is more important in the generation of ocean crust at this slow-spreading ridge than previously suspected.

show abstract

“…The scientific contributions of hydroacoustic studies have been numerous. For example, they have revolutionized our understanding of mid-ocean ridge eruptive processes (e.g., Fox et al, 1995;Dziak and Fox, 1999), illuminated the impact of submarine earthquakes on hydrothermal systems (e.g., Johnson et al, 2000;Dziak et al, 2003), addressed a wide variety of tectonic problems (e.g., Smith et al, 2002;Bohnenstiehl et al, 2002Bohnenstiehl et al, , 2004Dziak, 2006), and recently demonstrated the predictability of earthquakes on oceanic transform faults (McGuire et al, 2005). Because the Navy does not archive the SOSUS records, the near continuous 20-year library of North Pacific SOSUS digital data collected by NOAA/OSU represents a globally unique earthquake and ocean acoustic data set.…”

mentioning

confidence: 99%

A 20-Year Hydroacoustic Time Series of Seismic and Volcanic Events in the Northeast Pacific Ocean

Dziak¹,

Hammond²,

Fox³

2011

Oceanog.

View full text Add to dashboard Cite

Hydroacoustic monitoring of seismicity at the slow‐spreading Mid‐Atlantic Ridge

Cited by 92 publications

References 17 publications

Central role of detachment faults in accretion of slow-spreading oceanic lithosphere

Central role of detachment faults in accretion of slow-spreading oceanic lithosphere

Widespread active detachment faulting and core complex formation near 13° N on the Mid-Atlantic Ridge

A 20-Year Hydroacoustic Time Series of Seismic and Volcanic Events in the Northeast Pacific Ocean

Contact Info

Product

Resources

About