The effect of internal gas pressurization on volcanic edifice stability: evolution towards a critical state

Temperature plays a critical role in defining the seismogenic zone, the area of the crust where earthquakes most commonly occur; however, thermal controls on fault ruptures are rarely observed directly. We used a rapidly deployed seismic array to monitor an unusual earthquake cascade in 2018 at Lombok, Indonesia, during which two magnitude 6.9 earthquakes with surprisingly different rupture characteristics nucleated beneath an active arc volcano. The thermal imprint of the volcano on the fault elevated the base of the seismogenic zone beneath the volcanic edifice by 8 km, while also reducing its width. This thermal “squeezing” directly controlled the location, directivity, dynamics, and magnitude of the earthquake cascade. Earthquake segmentation due to thermal structure can occur where strong temperature gradients exist on a fault.

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Non-uniqueness of critical state line in compression and extension conditions

International Journal for Numerical and Analytical Methods in Geomechanics ◽

10.1002/nag.770 ◽

2009 ◽

Vol 33 (10) ◽

pp. 1315-1338 ◽

Cited By ~ 28

Author(s):

Zhen-Yu Yin ◽

Ching S. Chang

Keyword(s):

Critical State

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Recommended Procedures to Assess Critical State Locus from Triaxial Tests in Cohesionless Remoulded Samples

Geotechnics ◽

10.3390/geotechnics1010006 ◽

2021 ◽

Vol 1 (1) ◽

pp. 95-127

Author(s):

António Viana da Fonseca ◽

Diana Cordeiro ◽

Fausto Molina-Gómez

Keyword(s):

Critical State ◽

Review Paper ◽

State Theory ◽

Soil Freezing ◽

Triaxial Tests ◽

Cohesionless Soils ◽

Saturation Condition ◽

Testing Procedures ◽

Laboratory Procedures ◽

Soil Behaviour

The critical state theory is a robust conceptual framework for the characterisation of soil behaviour. In the laboratory, triaxial tests are used to assess the critical state locus. In the last decades, the equipment and testing procedures for soil characterisation, within the critical state framework, have advanced to obtain accurate and reliable results. This review paper summarises and describes a series of recommended laboratory procedures to assess the critical state locus in cohesionless soils. For this purpose, results obtained in the laboratory from different cohesionless soils and triaxial equipment configurations are compiled, analysed and discussed in detail. The procedures presented in this paper reinforce the use of triaxial cells with lubricated end platens and an embedded connection piston into the top-cap, together with the verification of the full saturation condition and the measurement end-of-test water content—preferable using the soil freezing technique. The experimental evidence and comparison between equipment configurations provide relevant insights about the laboratory procedures for obtaining a reliable characterisation of the critical state locus of cohesionless geomaterials. All the procedures recommended herein can be easily implemented in academic and commercial geotechnical laboratories.

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