Infrastructure and evolution of ocean-ridge discontinuities in Iceland

Guðmundsson, Ágúst

doi:10.1016/j.jog.2006.09.002

Cited by 72 publications

(48 citation statements)

References 43 publications

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“…Additionally, in both outcrop and thin-section scale, fl ow-top breccias show no evidence that there has been shear strain across them. Evidence for no slip on lava fl ow contacts has been observed in other steeply dipping lava fl ow sequences in Iceland as well (Gudmundsson, 2007b).…”

Section: Deformation Structuresmentioning

confidence: 59%

“…Several enigmatic, more steeply dipping (up to ~40°), axial "fl exure zones" (Gudmundsson, 2007b;Jóhannes son andSaemundsson, 1998a, 1998b;Saemundsson, 1979) present in the Pleistocene and older lava piles are, to date, the most steeply dipping lava sequences described in Iceland. The dip of individual lava fl ows within these inward-dipping sequences increases down section, indicat-ing that as the Icelandic crust is created during plate spreading, it undergoes time-progressive, subaxial subsidence (Bodvarsson and Walker, 1964;Pálmason, 1980).…”

Section: Background Crustal Accretion In Icelandmentioning

confidence: 91%

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Subvolcanic subsidence and caldera formation during subaerial seafloor spreading in Iceland

Siler

Karson

2012

Geological Society of America Bulletin

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Section: Deformation Structuresmentioning

confidence: 59%

Section: Background Crustal Accretion In Icelandmentioning

confidence: 91%

Subvolcanic subsidence and caldera formation during subaerial seafloor spreading in Iceland

Siler

Karson

2012

Geological Society of America Bulletin

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“…It is made of en-échelon, right-stepping, and left-stepping, NW-SE dextral strike-slip fault segments (Gudmundsson et al, 1993;Gudmundsson, 2007), which separate Tertiary rocks to the north from Upper Pleistocene rocks to the south (Saemundsson, 1974;Garcia et al, 2002). This fault is marked by land surface depressions occupied by lakes (sag ponds) with an estimated component of vertical offset at the surface that amounts to 200 m (Gudmundsson et al, 1993).…”

Section: Geologic-tectonic Frameworkmentioning

confidence: 99%

“…This type of configuration is stable with the slip vector of the rift coinciding with the slip vector of the transform fault, especially if simplified as the scheme of Figure 1C. This scheme works also on a regional scale, like in the case of the Tjörnes transform fault zone (TFZ) that connects the Kolbeinsey ridge, a mid-ocean ridge off the north coast of Iceland, with the rift zone in North Iceland (Gudmundsson, 2007). However, if a more local scale is considered, the connection between a transform fault and a rift can be much more complex, especially if this is studied onshore with a detail that cannot be obtained in offshore settings.…”

Section: Introductionmentioning

confidence: 96%

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

2016

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We present a detailed field structural survey of the area of interaction between the active NW-striking transform Husavik-Flatey Fault (HFF) and the N-S Theystareykir Fissure Swarm (TFS), in North Iceland, integrated by analog scaled models. Field data contribute to a better understanding of how transform faults work, at a much higher detail than classical marine geophysical studies. Analog experiments are conducted to analyse the fracture patterns resulting from different possible cases where transform faulting accompanies or postpones the rift motions. Different tectonic block configurations are also considered and results are compared with field data in order to study as thoroughly as possible the interaction between the HFF and the TFS as well as the possible prolongation of the HFF into the TFS. West of the intersection between the transform fault (HFF) and the rift zone (TFS), the former splays with a gradual bending giving rise to a leading extensional imbricate fan. The westernmost structure of the rift, the N-S Gudfinnugja Fault (GF), is divided into two segments: the southern segment makes a junction with the HFF and is part of the imbricate fan; north of the junction instead, the northern GF appears right-laterally offset by about 20 m. Southeast of the junction, along the possible prolongation of the HFF across the TFS, the strike of the rift faults rotates in an anticlockwise direction, attaining a NNW-SSE orientation. Moreover, the TFS faults north of the HFF prolongation are fewer and have smaller offsets than those located to the south. Through the comparison between the structural data collected in the field at the HFF-TFS connection zone and a set of scaled experiments, we confirm a prolongation of the HFF through the rift, although here the transform fault has a much lower slip-rate than west of the junction. Our data suggest that transform fault terminations may be more complex than previously known, and propagate across a rift through a modification of the rift pattern.

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“…The nearly north-south alignment, indicated from the hypocenters of post-Tohoku seismicity and lowfrequency earthquakes (Fig. 7), suggests that magma ascended slightly along a weak zone, namely the source regions of the post-Tohoku earthquakes, including a Mw 5.9 fault and low-frequency earthquakes, similar to transform-parallel dikes (Gudmundsson 2007). Although it is unclear when the weak zone began to form, this could be a representative magma pathway for past or future activity.…”

Section: Statistical Analysis Of Seismicity After the 2011 Tohoku Earmentioning

confidence: 92%

Elastostatic effects around a magma reservoir and pathway due to historic earthquakes: a case study of Mt. Fuji, Japan

Hosono

Mitsui

Ishibashi

et al. 2016

Prog. in Earth and Planet. Sci.

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We discuss elastostatic effects on Mt. Fuji, the tallest volcano in Japan, due to historic earthquakes in Japan. The 1707 Hoei eruption, which was the most explosive historic eruption of Mt. Fuji, occurred 49 days after the Hoei earthquake (Mw 8.7) along the Nankai Trough. It was previously suggested that the Hoei earthquake induced compression of a basaltic magma reservoir and unclamping of a dike-intruded region at depth, possibly triggering magma mixing and the subsequent Plinian eruption. Here, we show that the 1707 Hoei earthquake was a special case of induced volumetric strain and normal stress changes around the magma reservoir and pathway of Mt. Fuji. The 2011 Tohoku earthquake (Mw 9), along the Japan Trench, dilated the magma reservoir. It has been proposed that dilation of a magma reservoir drives the ascent of gas bubbles with magma and further depressurization, leading to a volcanic eruption. In fact, seismicity notably increased around Mt. Fuji during the first month after the 2011 Tohoku earthquake, even when we statistically exclude aftershocks, but the small amount of strain change (< 1 μ strain) may have limited the ascent of magma. For many historic earthquakes, the magma reservoir was compressed and the magma pathway was wholly clamped. This type of interaction has little potential to mechanically trigger the deformation of a volcano. Thus, Mt. Fuji may be less susceptible to elastostatic effects because of its location relative to the sources of large tectonic earthquakes. As an exception, a possible local earthquake in the Fujikawa-kako fault zone could induce a large amount of magma reservoir dilation beneath the southern flank of Mt. Fuji.

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Infrastructure and evolution of ocean-ridge discontinuities in Iceland

Cited by 72 publications

References 43 publications

Subvolcanic subsidence and caldera formation during subaerial seafloor spreading in Iceland

Subvolcanic subsidence and caldera formation during subaerial seafloor spreading in Iceland

Interaction between Transform Faults and Rift Systems: A Combined Field and Experimental Approach

Elastostatic effects around a magma reservoir and pathway due to historic earthquakes: a case study of Mt. Fuji, Japan

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