Superbrittleness of rocks and earthquake activity

Тарасов, Б. Г.; Randolph, Mark

doi:10.1016/j.ijrmms.2011.06.013

Cited by 80 publications

(38 citation statements)

References 31 publications

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“…Experiments (Tarasov 2010;Tarasov & Randolph 2011) have shown that the efficiency of the fan-mechanism depends on the rock strength: the stronger the rock, the greater the fan-mechanism efficiency and the wider the confining pressure range over which the fan-mechanism is active (see Figure 22). Figure 39(a) illustrates schematically depth distributions of the fan-mechanism activity for four rocks characterised by different strength, with strength increasing from rock 1 to rock 4.…”

Section: Earthquakes In Complex Crust Consisting Of Two Layers Of Difmentioning

confidence: 99%

“…Despite the Class II behaviour, post-peak control is achievable for rocks of this hardness. Analysis of available experimental data and additional experimental studies conducted in Tarasov (2010) and Tarasov and Randolph (2011), show that post-peak properties of hard rocks characterised by UCS > 250 MPa are still experimentally unexplored at highly confined compression corresponding to earthquake seismogenic depths and similar highly confined stress conditions in deep mines. These rocks are normally represented by highly metamorphic and volcanic rocks with fairly fine grains forming a very compact structure.…”

Section: Introductionmentioning

confidence: 99%

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Shear ruptures of extreme dynamics in laboratory and natural conditions

Тарасов¹

2017

Proceedings of the International Conference on Deep and High Stress Mining

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In the Earth's crust shear ruptures are responsible for macroscopic dynamic failure causing earthquakes. Shear ruptures induced by and triggered by the mining-induced stress change sometimes result in damaging rockbursts. The fundamental mechanism of the shear rupture is critically linked to the magnitude of ground motion, and hence, any resulting damage. For the effective management of seismic hazard both from natural and mining-related causes, a comprehensive understanding of the fundamental mechanism of the shear rupture is crucial. In recent years it has been observed that shear ruptures can propagate with extreme velocities exceeding the shear wave speed. Experiments show that a remarkable feature of extreme ruptures is the fact that friction reduces toward zero in the rupture head. Coseismic reduction in friction is critical in accelerating the fault slip and to the magnitude of ground shaking which affects the amount of potential earthquake and rockburst damage. Despite the critical importance, physical processes which determine the dramatic weakening of friction are still unclear and continue to be vigorously debated. The second unresolved question is about the source of energy which provides extreme rupture dynamics. This paper shows that the nature of extreme ruptures in intact rocks and in pre-existing faults with frictional and coherent interfaces is the same. It demonstrates that in all types of extreme ruptures, the fault weakening can be explained by a recently-proposed shear rupture mechanism associated with the intensive tensile-cracking process in the rupture tip observed for all extreme ruptures. The tensile-cracking process creates, in certain conditions, a fan-like fault structure, the shear resistance of which is extremely low. The fan-structure represents the basis of a self-sustaining natural mechanism of stress intensification in the rupture head providing the driving power for rupture propagation with extreme velocities. The fan-mechanism causes dramatic embrittlement of intact hard rocks under high stress and makes transient strength of intact hard rocks during the rupture propagation significantly less than the frictional strength. This paper introduces features of the fan-mechanism operation in primary ruptures and in natural complex faults and proposes an alternative view on the nature of earthquakes and shear rupture rockbursts generated by extreme ruptures.

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Section: Earthquakes In Complex Crust Consisting Of Two Layers Of Difmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Shear ruptures of extreme dynamics in laboratory and natural conditions

Тарасов¹

2017

Proceedings of the International Conference on Deep and High Stress Mining

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“…The work of Tarasov (Tarasov, 2010(Tarasov, , 2011Tarasov and Randolph, 2011;Tarasov and Potvin, 2012) provided evidence that for brittle rock under triaxial compression, a significant portion of the stored elastic strain energy is not consumed during the fracturing process. The unconsumed energy or the 'released energy' can then be transformed into the failure process dynamics, particularly associated with fragmentation, flying fragments, seismicity, heat, etc.…”

Section: 5mentioning

confidence: 99%

Towards an understanding of dynamic demand on ground support

Potvin

Wesseloo

2013

Proceedings of the Seventh International Symposium on Ground Support in Mining and Underground Construction

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The proper understanding of the functioning of ground support under dynamic loading and the current approaches to designing of dynamic support is plagued by a great deal of uncertainty and lack of knowledge. This applies equally to the understanding of the support capacity as well as the demand placed on to the support due to dynamic loading. Stacey (2012) suggests that the lack of understanding currently leads to a case of design indeterminacy. This paper does not aim to solve this problem of design indeterminacy but to explore some of the issues that need considerations to better understand the dynamic demand on ground support systems.

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“…The paper discusses a recently identified shear rupture mechanism operating in hard rocks under high σ 3 that is responsible for extreme rupture dynamics [16][17][18][19][20][21][22][23]. The mechanism was identified on the basis of comprehensive analysis of side effects accompanying extreme ruptures.…”

Section: Introductionmentioning

confidence: 99%

Dramatic Weakening and Embrittlement of Intact Hard Rocks in the Earth’s Crust at Seismic Depths as a Cause of Shallow Earthquakes

Тарасов¹

2019

Earth Crust

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Frictional stick-slip instability on pre-existing faults is well studied experimentally and considered as the general mechanism for shallow earthquakes. At the same time, post-peak properties of intact hard rocks under high confining stresses σ 3 corresponding to seismic depths of shallow earthquakes are still unexplored experimentally due to uncontrollable and violent failure of rock specimens even on modern stiff and servocontrolled testing machines. The lack of knowledge about post-peak properties of the majority of the earthquake host rocks prevents us from understanding and quantifying the contribution of these rocks to shallow earthquakes. This paper discusses a recently identified shear rupture mechanism operating in hard rocks under high σ 3 which causes dramatic rock weakening and embrittlement (by tenths of times) during the post-peak failure. The unknown before 'abnormal' properties of hard rocks imply the fundamentally different general mechanisms for shallow earthquakes. It is shown that in the earth's crust, the new mechanism acts in the vicinity of pre-existing faults only and provides the formation of new dynamic faults in intact rocks at very low shear stresses (significantly less than the frictional strength). The fault propagation is characterised by extremely low rupture energy and small stress drop. These 'abnormal' properties make hard rocks the main and more dangerous source of shallow earthquakes in comparison with pre-existing faults.

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Superbrittleness of rocks and earthquake activity

Cited by 80 publications

References 31 publications

Shear ruptures of extreme dynamics in laboratory and natural conditions

Shear ruptures of extreme dynamics in laboratory and natural conditions

Towards an understanding of dynamic demand on ground support

Dramatic Weakening and Embrittlement of Intact Hard Rocks in the Earth’s Crust at Seismic Depths as a Cause of Shallow Earthquakes

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