Causes of volcanic unrest at Mt. Spurr in 2004–2005 inferred from repeated tomography

Koulakov, Ivan; Smirnov, S. Z.; Gladkov, Valery; Kasatkina, Ekaterina; West, M. E.; Khrepy, Sami El; Al-Arifi, Nassir

doi:10.1038/s41598-018-35453-w

Cited by 26 publications

(24 citation statements)

References 27 publications

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“…At shallower depths, beneath Koryaksky, we observe dominantly low values of the Vp/Vs ratio in a range of 1.7–1.8. Similar transition from high to low values of the Vp/Vs ratio can be observed in some other active volcanoes, such as Mount Spurr (Koulakov et al, ) and Gorely (Kuznetsov et al, ). In many cases, such low Vp/Vs anomalies are explained by degassing of fluid saturated magmas during ascent and decompression.…”

Section: Discussionsupporting

confidence: 76%

“…At the same time, S wave velocity is primarily sensitive to the presence of liquids in the form of either volatiles or melts (e.g., Takei, ). Together, high Vp and low Vs result in a very high Vp/Vs anomaly, frequently observed at many active volcanoes, such as Nevado del Ruiz in Colombia (Vargas et al, ), Mount Spurr in Alaska (Koulakov et al, ), and Klyuchevskoy volcano (Koulakov et al, ).…”

Section: Discussionmentioning

confidence: 97%

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Tomographic Images of Magma Chambers Beneath the Avacha and Koryaksky Volcanoes in Kamchatka

et al. 2019

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A new tomographic model (Vp, Vs, and Vp/Vs ratio) was built for two neighboring active volcanoes, Avacha and Koryaksky, which represent a serious hazard to the population and infrastructure of Petropavlovsk‐Kamchatsky, the main city of Kamchatka, Russia. Arrival times of seismic P and S waves from almost 5,000 local events, recorded by a permanent network of seismic stations during 2009–2018, were used for tomography. The resolution of the derived models was carefully tested by a series of synthetic simulations. Prominent anomalies with extremely high Vp/Vs ratios (up to 2.4) were retrieved directly beneath both volcanoes and interpreted as magma reservoirs containing high degrees of partial melt and/or fluids. Beneath Avacha, the upper limit of the anomaly is located at the depth of ~2 km below the surface. The reservoir appears to be connected to the surface by a neck‐shaped anomaly of high Vp/Vs ratio associated with active seismicity, which is interpreted as a magma and fluid conduit. Beneath Koryaksky, the magma related anomaly is deeper: Its upper limit is located at a depth of ~7 km below the surface. This anomaly is connected with the volcanic cone and is associated with a vertical seismicity cluster, which possibly marks the pathway of fluid ascent and degassing. Between the volcanoes, a 2‐ to 3‐km thick layer of very low Vp and Vs is interpreted as deposits of volcanoclastic sediments. Generally low Vp/Vs ratios in the area between the volcanoes show that the magma reservoirs in the upper crust are not interconnected.

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Section: Discussionsupporting

confidence: 76%

Section: Discussionmentioning

confidence: 97%

Tomographic Images of Magma Chambers Beneath the Avacha and Koryaksky Volcanoes in Kamchatka

et al. 2019

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“…In our results, beneath HSV, we observe a prominent low‐ Vp/Vs ratio (less than 1.5). Such a low Vp/Vs ratio could be interpreted as a signature of gas contamination, as was observed in some previous tomography studies of volcanoes with high levels of gas emission (Husen et al., 2004; Koulakov et al., 2013, 2018; Kuznetsov et al., 2017). At the same time, in the geothermal sources of HSBV, there is no evidence of gases coming from deeper layers.…”

Section: Discussionsupporting

confidence: 64%

Magma‐Fluid Interactions Beneath Akutan Volcano in the Aleutian Arc Based on the Results of Local Earthquake Tomography

2021

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Volcanoes in the Aleutian arc and Alaska are located in low-populated areas; nevertheless, they represent serious hazard to the local population and infrastructure, as well as to the air traffic along dense aviation routes in the northern Pacific (Casadevall, 1993). To enable fast detection of ongoing volcanic eruptions, most active volcanoes in these regions are equipped with telemetered seismic networks that continuously transmit the records to the offices of the Alaska Volcano Observatory (AVO), where they are processed in real time (Dixon et al., 2019). Besides the hazard assessment, the data recorded by these networks are used for studying fundamental aspects of functioning magma plumbing systems, which still remain poorly understood due to their complexity. Mechanical, chemical, and thermal interactions of materials in the magmatic systems require multidisciplinary approaches, in which geophysical imaging of structures beneath volcanoes is one of the essential elements. In this study, we investigate the upper-and middle-crustal structure beneath Akutan Island located in the eastern part of the Aleutian arc (Figure 1a). This island hosts Akutan volcano, which is one of the most active in the Aleutian arc, with dozens of documented eruptions starting from the eighteenth century (Siebert & Simkin, 2013). These eruptions were mostly weak or moderate; however, the existence of a Holocene caldera with a diameter ∼2 km and thick scoria-bearing, lapilli tephra (Akutan tephra) widely spreading over the entire island surface (Waythomas, 1999) indicates that Akutan has a serious potential for explosive caldera-forming eruptions. During the past century, Akutan demonstrated variable styles of volcanic activity, such as lava flows, gas emissions, and strombolian explosive eruptions ejecting ash plumes (e.g., Miller et al., 1998). The most recent eruption of Akutan occurred in 1992. However, after this, in March 1996, a remarkable episode of seismic unrest occurred, which did not lead to a volcanic eruption, but caused earthquakes with magnitudes of up to M5.3 and triggered strong ground deformations (Lu et al., 2000, 2005). These and other aspects of Akutan's activity are discussed in more detail in the next section.

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“…The resulting very low Vp/Vs ratio (1.5–1.55) indicates that the related medium behaves as a gas-filled sponge that strongly slows down the pressure waves 45 . In the literature, there are several examples of volcanoes with a high degassing level, such as Yellowstone 46 , Campi Flegrei 47 , Gorely 48 , Nevado del Ruiz 7 , and Mount Spurr 49 , for which seismic tomography revealed similar anomalies of low Vp/Vs ratio interpreted as gas storages. Thus, our model shows the existence of both magma and gas reservoirs that are spatially separated but located at the same depth of 2–3 km below the surface of Bezymianny.…”

Section: Discussionmentioning

confidence: 99%

Anatomy of the Bezymianny volcano merely before an explosive eruption on 20.12.2017

Koulakov

Plechov

Mania

et al. 2021

Sci Rep

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Strong explosive eruptions of volcanoes throw out mixtures of gases and ash from high-pressure underground reservoirs. Investigating these subsurface reservoirs may help to forecast and characterize an eruption. In this study, we compare seismic tomography results with remote sensing and petrology data to identify deep and subaerial manifestations of pre-eruptive processes at Bezymianny volcano in Kamchatka shortly before its violent explosion on December 20, 2017. Based on camera networks we identify precursory rockfalls, and based on satellite radar data we find pre-eruptive summit inflation. Our seismic network recorded the P and S wave data from over 500 local earthquakes used to invert for a 3D seismic velocity distribution beneath Bezymianny illuminating its eruptive state days before the eruption. The derived tomography model, in conjunction with the presence of the high-temperature-stable SiO2 polymorph Tridymite in juvenile rock samples , allowed us to infer the coexistence of magma and gas reservoirs revealed as anomalies of low (1.5) and high (2.0) Vp/Vs ratios, respectively, located at depths of 2–3 km and only 2 km apart. The reservoirs both control the current eruptive activity: while the magma reservoir is responsible for episodic dome growth and lava flow emplacements, the spatially separated gas reservoir may control short but powerful explosive eruptions of Bezymianny.

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Causes of volcanic unrest at Mt. Spurr in 2004–2005 inferred from repeated tomography

Cited by 26 publications

References 27 publications

Tomographic Images of Magma Chambers Beneath the Avacha and Koryaksky Volcanoes in Kamchatka

Tomographic Images of Magma Chambers Beneath the Avacha and Koryaksky Volcanoes in Kamchatka

Magma‐Fluid Interactions Beneath Akutan Volcano in the Aleutian Arc Based on the Results of Local Earthquake Tomography

Anatomy of the Bezymianny volcano merely before an explosive eruption on 20.12.2017

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