Ambient-noise tomography of Katla volcano, south Iceland

Jeddi, Zeinab; Guðmundsson, Ólafur; Tryggvason, Ari

doi:10.1016/j.jvolgeores.2017.09.019

Cited by 17 publications

(10 citation statements)

References 64 publications

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“…Some rhyolite is found exposed in the area according to the geological map of Jóhannesson (2014). Therefore, we suggest that this anomaly may relate to a poorly exposed Tertiary volcanic center, i.e., it cumulates beneath a relic shallow magma reservoir similar to the one mapped by Brandsdóttir et al (1997) beneath Krafla volcano and by Jeddi et al (2017) at Katla. Similar, but less pronounced high-velocity anomalies underneath the Flateyjarskagi and Tjörnes Peninsulas may have the same explanation.…”

Section: Discussionmentioning

confidence: 73%

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Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)

et al. 2021

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The Tjörnes Fracture Zone (TFZ) is a transform zone that connects the Kolbeinsey Ridge (KR) to the Northern Volcanic Zone (NVZ) of Iceland. The TFZ has two main sub-parallel structures approximately oriented SE-NW: the Húsavík Flatey Fault (HFF) and the Grímsey Oblique Rift (GOR). Additionally, the KR continues to the south as the Eyjafjarðaráll Rift (ER) on the western border of the TFZ. Together these parts of the TFZ demark the Tjörnes Microplate (TM) (see Figure 1). The HFF, the GOR and the ER encompass most of the seismicity in the region (Figure 2). The seismicity of the area is characterized by the SIL earthquake catalog of the Icelandic Meteorological Office (IMO) (Bödvarsson et al., 1999;Rögnvaldsson et al., 1998).The HFF is a WNW-striking, right-lateral strike-slip fault that extends from the Þeistareykir fissure swarm in the NVZ to the southern end of the ER. The eastern part of the HFF is a set of subparallel faults located on land on the Tjörnes Peninsula. The central and western parts are located offshore (Figure 1). The ER is a pull-apart basin characterized by a semi-symmetric pattern of normal faulting on a north-striking axis Abstract Local earthquake tomography has been carried out in the Tjörnes Fracture Zone. This transform region connects the Mid-Atlantic Ridge to the Northern Volcanic Zone in Iceland in a mostly offshore area. The challenge to record seismic information in this area was the motivation for the North ICeland Experiment (NICE). Fourteen ocean-bottom seismometers and eleven on-land stations were installed in the project and operated simultaneously with the permanent Icelandic seismic network (SIL) during summer 2004. Data from the experiment were used to estimate P-and S-wave crustal velocities. Also, the gravity anomaly was derived for comparison with the tomographic results. Upper-crustal velocities are found to be relatively low in the offshore region. In particular, low velocities are mapped along the Húsavík-Flatey Fault, where a more confined negative gravity anomaly and a sedimentary basin are found. Low velocities are also mapped along the Grímsey Oblique Rift and in a zone connecting these two main lineaments. The northern half of the aseismic Grímsey Shoal appears as a fast anomaly. Furthermore, localized high-velocity anomalies are found beneath northern Tröllaskagi and Flateyjarskagi Peninsulas, where bedrock dates from Upper and Middle Miocene (10-15 Ma). Regions of low Vp/Vs ratios are mapped at depth along the main lineaments. Low velocities along the lineaments are interpreted as due to fracturing extending into the middle crust, while high velocities in the upper crust beneath Tertiary formations are associated with relic volcanoes. Low Vp/Vs variations along the lineaments are interpreted as due to the presence of supercritical fluids.

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Section: Discussionmentioning

confidence: 73%

“…(1997) beneath Krafla volcano and by Jeddi et al. (2017) at Katla. Similar, but less pronounced high‐velocity anomalies underneath the Flateyjarskagi and Tjörnes Peninsulas may have the same explanation.…”

Section: Discussionmentioning

confidence: 96%

Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)

et al. 2021

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“…For Rayleigh waves, these retrieved velocities correspond predominantly to the shear wave velocity. Ambient noise tomography has been applied to many types of studies, primarily in seismology, to image large crustal-scale structures (Gudmundsson et al, 2007;Lin et al, 2008;Shapiro et al, 2005;Yao et al, 2006), but also at smaller scale, especially to image the subsurface of volcanic islands (Brenguier et al, 2007;Jeddi et al, 2017;Lee et al, 2021;Luzón et al, 2011;Matos et al, 2015;Mordret et al, 2015;Obermann et al, 2016;Ryberg et al, 2017;Villagómez et al, 2011). In recent years, the value of ambient noise tomography for studying high-resolution near-surface structures has been recognized (Chmiel et al, 2019;de Ridder & Dellinger, 2011;Lin et al, 2013;Mordret et al, 2013;Picozzi et al, 2009), but applications for hydrological purposes are still very scarce.…”

Section: Ambient Noise Surface Wave Tomographymentioning

confidence: 99%

A Multi‐Hydrogeophysical Study of a Watershed at Kaiwi Coast (Oʻahu, Hawaiʻi), using Seismic Ambient Noise Surface Wave Tomography and Self‐Potential Data

Grobbe

Mordret

Barde-Cabusson

et al. 2021

Water Resources Research

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As a Pacific Island, Hawaiʻi's hydrological processes are influenced by strong spatio-temporal gradients in, and close interactions between, rainfall, land-use, near-surface geological conditions, and complicated subsurface hydrogeology. Due to their volcanic nature, the hydrogeology of Hawaiʻi predominantly consists of basaltic bedrock formations that vary in terms of, for example, the type of lava flow deposit ('A'ā vs. Pāhoehoe), age, and thickness of individual flow units. Several factors, such as the age of the islands and climatic variability, control regolith development, and its characteristics (Ryu et al., 2014;P. Vitousek, 2004).Hawaiian hydrogeology possesses strong spatio-temporal gradients and heterogeneity at a variety of spatial scales (Figure 1). For example, basaltic formations are dominated by both small-and intermediate-scale fractures and large-scale faults that strongly affect chemical fate and transport processes (Deng & Spycher, 2019). Mechanical weathering and chemical alteration create saprolite layers with low hydraulic conductivity, forming barriers to flow (Figure 1) and/or causing groundwater to be trapped in perched formations (Hunt, 1996;Mink & Lau, 1980;Oki, 2005). On the island of Oʻahu, as well as on other Pacific islands, valley-ridge complexes are known to generate highly complicated groundwater systems (Oki, 2005). Older alluvium deposits, created during periods of extensive erosion that carved deep valleys in the original volcanoes, are of hydrological importance due to their relatively low hydraulic conductivity, estimated to be in the range of 3.96 × 10 −3 m/day (0.013 ft/day) to 0.33 m/day (1.08 ft/day) (Wentworth, 1938). The low permeability is related to chemical alteration, weathering, and compaction (Oki, 2005;Wentworth, 1951).

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“…An example is a pioneering work of mapping the Piton de la Fournaise volcano (La Reunion) described by Brenguier et al (2007), which constrained a high-velocity anomaly caused by rising magma surrounded by the effusive materials that build the volcano. Some recent works using ambient noise tomography in volcanoes can be found in Gao and Shen (2015), Guidarelli and Aoudia (2016), Jeddi et al (2017), Benediktsdóttir et al (2017), andChen et al (2018). Currently, SI has been used at volcanic sites to monitor variations in pressure, and transport of magma, and to predict eruptions (Taira and Brenguier 2016;De Plaen et al 2016;Donaldson et al 2017).…”

Section: Seismic Interferometry Backgroundmentioning

confidence: 99%

Ambient noise tomography of the Popocatépetl volcano using the principal Green tensor components

et al. 2021

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A 3D shear wave velocity model of the subsurface of Popocatépetl volcano was obtained using ambient noise tomography, employing the principal cross-terms of the empirical Green's function. Daily cross-correlation waveforms were computed from the data recorded by four seismic broadband stations in 2012. Dispersion curves were estimated from the stack of anti-causal and causal parts for the three ground motion components. In the period ranging between 0.5 and 7 s, the radial component provided the most welldefined group velocity dispersion curves for Rayleigh waves. Dispersion curves for long paths (> 9.5 km) suggested the presence of a layered structure with group velocity values ranging from 0.5 to 3.0 km/s. Dispersion curves for short paths (< 7 km) and close to the volcano showed values similar to those for long paths but with a velocity inversion occurring between 3-and 5-s periods. Despite the scarce ray-path coverage, a tomography inversion provided the means to image an S-wave velocity anomaly (2.5-3.0 km/s) in the northern part of the crater at depths not larger than 6 km. The volcanotectonic seismicity during 2012-2013 was found to be concentrated in the southern segment of this anomaly, which seems to mark a boundary between a solidified body (possibly a product of ancient volcanic craters) and the softer material.

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Ambient-noise tomography of Katla volcano, south Iceland

Cited by 17 publications

References 64 publications

Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)

Local Earthquake Tomography in the Tjörnes Fracture Zone (North Iceland)

A Multi‐Hydrogeophysical Study of a Watershed at Kaiwi Coast (Oʻahu, Hawaiʻi), using Seismic Ambient Noise Surface Wave Tomography and Self‐Potential Data

Ambient noise tomography of the Popocatépetl volcano using the principal Green tensor components

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