A note on thermoelastic strains and tilts

Berger, Jon

doi:10.1029/jb080i002p00274

Cited by 116 publications

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“…At the time of the writing (May 2013) the tilt signals were characterized only by oscillations of an amplitude smaller than 10 µrad and of a period of about 24 h. These signals are likely the response to the deformation produced by the thermo-elastic effect (e.g. Berger, 1975, Bonaccorso, 1999 induced by the diurnal temperature variation.…”

Section: Fogo and Brava Sub-networkmentioning

confidence: 99%

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Faria¹,

Fonseca²

2014

Nat. Hazards Earth Syst. Sci.

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Abstract. We describe a new geophysical network deployed in the Cape Verde Archipelago for the assessment and monitoring of volcanic hazards as well as the first results from the network. Across the archipelago, the ages of volcanic activity range from ca. 20 Ma to present. In general, older islands are in the east and younger ones are in the west, but there is no clear age progression of eruptive activity as widely separated islands have erupted contemporaneously on geological timescales. The overall magmatic rate is low, and there are indications that eruptive activity is episodic, with intervals between episodes of intense activity ranging from 1 to 4 Ma. Although only Fogo Island has experienced eruptions (mainly effusive) in the historic period (last 550 yr), Brava and Santo Antão have experienced numerous geologically recent eruptions, including violent explosive eruptions, and show felt seismic activity and geothermal activity. Evidence for recent volcanism in the other islands is more limited and the emphasis has therefore been on monitoring of the three critical islands of Fogo, Brava and Santo Antão, where volcanic hazard levels are highest. Geophysical monitoring of all three islands is now in operation. The first results show that on Fogo, the seismic activity is dominated by hydrothermal events and volcano-tectonic events that may be related to settling of the edifice after the 1995 eruption; in Brava by volcano-tectonic events (mostly offshore), and in Santo Antão by volcano-tectonic events, medium-frequency events and harmonic tremor. Both in Brava and in Santo Antão, the recorded seismicity indicates that relatively shallow magmatic systems are present and causing deformation of the edifices that may include episodes of dike intrusion.

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Section: Fogo and Brava Sub-networkmentioning

confidence: 99%

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Faria¹,

Fonseca²

2014

Nat. Hazards Earth Syst. Sci.

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“…In turn, this changes the elastic properties and the velocity of the medium. The subsurface temperature fluctuations were assumed to be spatially periodic, similar to the formulation of Berger (1975). These lateral variations are caused by topography and the presence of the ocean leading to high temperature variations in the mountains and low variations at the shoreline.…”

Section: Annual Velocity Changesmentioning

confidence: 99%

Field observations of seismic velocity changes caused by shaking-induced damage and healing due to mesoscopic nonlinearity

et al. 2016

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“…However, thermal stresses induced in the rock mass consist of a superposition of a bodyforce-like and a surface-traction-like term (e.g., Berger, 1975;Ben-Zion and Leary, 1986;Prawirodirdjo et al, 2006). Although the body-force-like term is due to the thermal expansion at a given point and travels with the slow velocity of the thermal front, the traction-like term is due to elastic coupling of thermal expansion at distant points and is instantaneously transmitted over large distances (Ben-Zion and Leary, 1986).…”

Section: Study Site and Monitoring Networkmentioning

confidence: 99%

Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

Cailleau¹,

Kaiser²,

Dahm³

2014

Bulletin of the Seismological Society of America

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Mining activity may cause different types of seismicity and rock failure.Typical events include (1) fully induced microearthquakes in close proximity to galleries and human activity due to high-stress concentrations (border fractures) and (2) triggered earthquakes within the rock mass at larger distance to the source of the stress perturbation (inner fractures). Type 1 is important to understand the development of rock bursts and evaluate the stability of the mine. Type 2 may be associated with larger events releasing pre-existing stress and being triggered by stress changes due to the mining operation. They are important to assess the seismic hazard related to mining activity.To analyze these different failure processes, we use a dataset of high-frequency acoustic emission (AE) events monitored in an abandoned salt mine. The process of fracture formation in the rock mass was enhanced by the backfilling of a cavity. Thermal stresses induced by the backfilling operation are modeled with a finite-element approach, and observed AE activity is used to quantify the mechanism of event triggering in terms of a Coulomb failure model.Two observations are outstanding. First, the instantaneous triggering of enhanced activity and the slow growth of an inner fracture in relatively far distance to the backfilled cavity is detected. The structure already showed AE activity before the refilling started and was triggered by traction-like stress transfer. Its AE activity correlates well with the calculated Coulomb stress changes at the beginning of backfilling. Second, the sudden occurrence of a macroscopic, induced border fracture at the backfilled gallery which is oriented in agreement with the acting stress field is observed. Although AE activity at the inner fracture was triggered by tiny Coulomb stress changes, indicating a structure already in critical state, formation of the border fracture required significantly larger stresses, hinting at a previously intact rock volume.Online Material: Figure depicting the variability of the static Coulomb stress changes on the inner fracture for different rake values.

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A note on thermoelastic strains and tilts

Cited by 116 publications

References 0 publications

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Investigating volcanic hazard in Cape Verde Islands through geophysical monitoring: network description and first results

Field observations of seismic velocity changes caused by shaking-induced damage and healing due to mesoscopic nonlinearity

Macroscopic Failure Processes at Mines Revealed by Acoustic Emission (AE) Monitoring

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