Hydromechanical coupling in tectonic faults and the origin of aseismic slip, quasi-dynamic transients and earthquake rupture

Project Information

HYQUAKE

Grant agreement ID: 101040600

DOI

10.3030/101040600

EC signature date 27 January 2022

Start date 1 June 2022

End date 30 November 2027

Funded under

• European Research Council (ERC)

Total cost

€ 1 462 710,00

EU contribution

€ 1 462 710,00

Coordinated by

UNIVERSITA DEGLI STUDI DI ROMA LA SAPIENZA
Italy

Periodic Reporting for period 1 - HYQUAKE (Hydromechanical coupling in tectonic faults and the origin of aseismic slip, quasi-dynamic transients and earthquake rupture)

Reporting period: 2022-06-01 to 2024-11-30

Summary of the context and overall objectives of the project

Earthquakes and tectonic fault slip are among the most hazardous and unpredictable natural phenomena. Understanding the role of fluids in tectonic faulting is crucial as recent research highlights their significance in both human-induced seismicity and various modes of fault slip, ranging from episodic tremor and slip to slow earthquakes. The HYQUAKE project aims to address the complexities of hydromechanical coupling in fault zones, which are not yet fully understood due to the inaccessibility of earthquake faults and the complex nature of the physical processes involved. The project focuses on developing a physically based framework to understand and predict fluid pressure-induced fault slip across a range of fault motions, from aseismic creep to destructive earthquakes. This interdisciplinary approach combines laboratory experiments, seismology, and data/computer science to provide unprecedented quantitative constraints on the physical processes that control earthquakes and fault slip behavior.

Objectives:

1. **Develop Predictive Models:** Build predictive, physics-based models for hydromechanical coupling in fault zones.
2. **Laboratory Experiments:** Conduct controlled rock deformation experiments to gather key data on fault zone elastic properties, frictional rheology, and hydromechanical parameters.
3. **Machine Learning Integration:** Use machine learning techniques to forecast lab-induced quakes based on experimental data.
4. **Acoustic Imaging:** Utilize novel acoustic techniques to image fault zone structure and fluid flow dynamics.

Expected Impact

The HYQUAKE project is expected to significantly advance our understanding of fluid-induced fault slip and its various manifestations, contributing to improved seismic hazard assessment and risk mitigation strategies. The project's outcomes are expected to benefit both the scientific community and society by:

1. **Enhancing Earthquake Prediction:** Developing models that can better predict the likelihood and characteristics of different types of fault slips.
2. **Mitigating Seismic Risks:** Providing insights that can help mitigate the risks associated with both natural and human-induced earthquakes.
3. **Interdisciplinary Contributions:** Integrating knowledge from seismology, rock physics, and data science to build comprehensive physical models of fault behavior.

Significance of the Project

The significance of HYQUAKE lies in its potential to bridge the gap between laboratory experiments and real-world seismic activity. By understanding the underlying physical processes and developing predictive models, the project aims to:

1. **Improve Seismic Forecasting:** Provide new methods for forecasting earthquakes, especially those induced by human activities.
2. **Inform Policy and Practice:** Offer data and models that can inform public policy and industry practices regarding fluid injection and other activities that affect seismicity.
3. **Advance Scientific Knowledge:** Contribute to the fundamental scientific understanding of fault mechanics and earthquake physics.

Conclusion

The HYQUAKE project represents a significant step forward in the study of earthquakes and fault slip mechanisms. By combining advanced laboratory techniques, machine learning, and acoustic imaging, it aims to develop comprehensive models that can predict and mitigate seismic hazards. The project's interdisciplinary approach and potential societal impact highlight its importance and relevance in today's world.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The first two years, HYQUAKE has been characterized by great advancements:

- Realization and patent for a new experimental sample configuration that is capable of measuring fault permeability anysotropy under realistic boundary conditions.
- Realization and testing of a new Acoustic Emission (AE) system. This system is capable of recording in continous mode at 6MHz and 14-bit resolution. To achieve this uncommon parameters we have used commercial digital oscilloscope that we have programmed in-house based on our needs.
- Implementation of a new framework to Calibrate Piezo Electric Transducers (PZT) that are analog of seismometers in the laboratory. This technical advancement allow us to accurately determine the frequency cantent and magnitude of laboratory earthquakes, allowing a comparison with natural seismicity and address the scaling of physical processes from the lab to nature.
- Realization and testing of ultrasonic wave testing system capable of imaging changes in fault physical properties during deformation at a rate of 10KHz.
- Implementation of Discrete Element Method Code (DEM) to simulate angular grains composing fault gouge that can break during shear deformation. This implementation is at the state-of-the-art of such codes and will shed light on the physical processes at the origin of shear localization.
- Implementation of a Boundary Element Method code to simulate multiple rough faults that can interact amongst each other during fluid injection. The stress state and loading condition are controlled by the diffusion of fluid upon injection of pressurized fluids and the fault frictional properties obey rate- and state friction constitutive equations. This approach is at the forefront of modeling and can accurately simulate realistic natural case scenarios based on laboratory derived friction parameters.
- Training of Phase-Net, A Deep-Neural-Network-Based Seismic Arrival Time Picking Method, upon laboratory waveform. It required the manual picking of ~50000 waveforms and associated noise.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

In the first two years HYQUAKE has already obtained some exceptional results:
- Understanding the role of stress perturbation on fault stability on a laboratory fault. We have experimentally and numerically shown that it exist a characteristic perturbation frequency that can trigger unstable fault slip. This has fundamental implication for dynamic triggering of earthquakes.
- By using calibrating PZTs we have demonstrated that in the laboratory exist a continuum of fault slip modes, from aseismic creep to dynamic ruptures, with fundamental implication for the physics of earthquake and faulting. We have shown that the moment and corner frequency scales with stress drop and can be represented by a continuum.