Editorial: Faults and earthquakes viewed by networks, monitoring systems and by numerical modelling techniques

1 Introduction

Rock rheology controls rock deformation caused by Earth’s internal forces. Rheology examines the relationships between stress (force per unit area) and strain rate (rate of deformation) in materials. Plate tectonics has shown that the complete explanation of the interaction of Earth’s lithosphere with mantle convection and other driving factors requires considering several other interacting factors beyond plate movement. The complicated deformation patterns of plate boundary zones, which space geodetic tools can now properly map, demonstrate this. Mineralogy, geofluid composition and content, mineral grain size, melt content, temperature, pressure, and differential stress affect rock rheology. Rocks exhibit considerable variability in their mineralogical and chemical composition, and our expanding knowledge of regional heat transport and tectonic stresses is of paramount importance. The upper mantle convection pattern under tectonic plates is not directly related to plate borders. Using geophysical factors like topography, gravity, S-wave dispersion, and heat flow, geological structures can be discovered and analyzed. However, earthquakes are the primary way to observe sudden movements occurring a few kilometers below the Earth’s surface. The link between earthquake depths and subduction speeds suggests the influence of temperature on seismic activity. This Research Topic seeks to understand what distinguishes seismic fault movement from creeping fault movement. Geofluid mapping has been utilized to identify areas of tectonic activity. Earthquakes persist in areas with significant tectonic activity, and geofluids will continue to contribute to the genesis of earthquakes until affected by major global geodynamic events.

This Research Topic presents the findings obtained using the latest geophysical, geochemical, geodetic, and statistical methodologies. Understanding the entire process—from nucleation to earthquake—is the goal. Recent annual meetings of the China Earthquake Prediction Forum, the Asia Oceania Geosciences Society, the European Geosciences Union, the American Geophysical Union, and others stressed the importance of observatory networks of monitoring systems from space, ground, and subsurface based on multiple sensors for potential anomalies related to inter-seismic (pre-seismic), co-seismic, and post-seismic processes and their spatial and temporal scales of numerical modeling of the physical processes of nucleation, dynamic rupturing, and seismic wave propagating of earthquakes.

2 Aims and content of this research topic

Goals and contents of this Research Topic “Faults and Earthquakes Viewed by Networks, Monitoring Systems, and Numerical Modeling Techniques” refer to recent research on earthquake processes which uses multidisciplinary approaches from geophysical, geochemical, geodetic, and geological parameters. Enhancing risk appraisal and prediction abilities is the most relevant disaster mitigation approach in seismically active locations. Multidisciplinary investigations of small-scale cracks in the laboratory and seismogenic features in field test locations have contributed to our comprehensive understanding of earthquake processes from preparation to faulting in recent decades. Pre-earthquake observations, methods, and perspectives can elevate our understanding of the processes preceding earthquakes. Modeling, which can be used to set up earthquake forecasting experiments, verifies test site areas of all sizes that are found globally in seismically active locations.

3 Overview of published contributions

This Research Topic compiles a total of 13 articles, involving geochemical and hydrogeological parameters in tectonically active areas (4 articles), ground deformations (2 articles), stress modeling (2 articles), source modeling (1 article), apparent resistivity of rocks (1 article), microseismic location (1 article), teleseismic location (1 article), and ground motion measurements (1 article).

3.1 High-potential precursors of earthquakes from geochemical and hydrogeological parameters

Li et al. examined the geochemical characteristics of fault zone gases and their implications for understanding fault activity and seismic events. Their study underscores the importance of isotope tracing in deciphering fluid sources, migration pathways, and the evolution of fault zones. Chen et al. assessed the sensitivity and validity of various geochemical parameters as monitoring and precursory tools in Beijing, a key seismic monitoring area.

Zhang et al. examined eight wells situated near the Longmenshan–Anninghe fault zone, which exhibit significant disparities in groundwater-level changes. The authors quantified the observed changes using the Molchan diagram and investigated potential factors influencing the changes using correlation analyses. Yang et al. analyzed five soil gas continuous monitoring stations to carry out observations of fault gas concentrations within the Yanqing fault zone. The results show that the time series of the hydrogen (H₂) gas concentration has a close relationship with local seismic activity and far-field strong earthquakes.

3.2 Ground deformation of earthquakes inferred from InSAR and GNSS measurements

Chen et al. introduced a novel fault co-seismic dislocation inversion method based on parallel elastic finite element simulations. The authors conducted inversion tests using various idealized fault models to validate their approach. Combining geodetic and seismological analyses, Lin et al. deduced that afterslip is the dominant mechanism of near- to intermediate-field post-seismic deformation and also likely represents the driving force that controls aftershock productivity and the spatiotemporal migration of seismicity.

3.3 Approaches to stress modeling using the proposed model and stress state

Xu and Zeng proposed a model to reveal the relationships between differential stress, seismicity, brittle–ductile transition, and boundary depth of the upper and lower crust in the continental crust and linked the multiple observations from geophysics and geology in Southeastern Tibetan Plateau. Lei et al. suggested that the high load/unload response ratio value before its decline may mark the end of the rock medium’s yielding phase, and Outgoing Longwave Radiation data can reflect, to some extent, the state of tectonic stress accumulating along active faults in a critical condition.

3.4 Favored model for source modeling

De Lorenzo and Michele proposed a new technique and applied it to a small-magnitude earthquake (ML3.3) that occurred in Central Italy. They identified the most likely rupture models and examined the issue of correlation among model parameters.

For the investigated event, a circular crack model was resulted favored over a heterogeneous rupture model.

3.5 Extracting the anomalies of apparent resistivity of rocks

Lei et al. provided a reference framework for earthquake precursor studies by demonstrating how to quantitatively remove environmental interference in anisotropy analyses and how to avoid areas with large local influences.

3.6 High-precision microseismic location

Wu et al. proposed a high-precision location algorithm for 3D Fast Sweeping Method seismic sources to develop a small-scale regional microseismic location model for coal mines.

3.7 Fast automatic determination of teleseismic location

Yuan et al. proposed a fully automatic approach by integrating the advantages of seismic scanning based on navigated automatic phase-picking, which can automatically detect and locate seismic events from continuous waveforms, and the depth-scanning algorithm, which can determine the precise focal depth of local and regional earthquakes by matching depth phases. This method can be used to establish high-quality teleseismic catalogs and depth-phase databases.

3.8 Ground motion measurements using a dense array

Zhou et al. deployed a seismic array in Gongquan Town to observe seismic activities and analyzed the amplification effects in the area. The research results from weak-motion seismograms of aftershocks indicate significant seismic ground motion amplification in Gongquan Town. The observed phenomenon highlights the need to pay special attention to the risk of significant damage caused by the combined effects of extreme amplification in future earthquake mitigation efforts.

4 Discussion and perspectives

The advancement of geosciences is built upon modern observational methodologies. Utilizing extensive laboratory experiments, several scientists have demonstrated that earthquakes may be preceded by potential precursors that might aid in forecasting. The prolonged accumulation of previous events has provided insights into the mechanisms underlying the preparation of significant earthquakes. This volume contains several unique concepts that can elevate the knowledge of earthquake mechanisms. This Research Topic emphasizes the complex nature of seismic activity and has favored submissions that employ geophysical, geochemical, and geodetic techniques to elucidate the earthquake process from nucleation to manifestation. The scope includes innovative research utilizing observation networks and sophisticated numerical modeling that synthesizes diverse data. A critical re-assessment of the suggested methodologies, along with cutting-edge and innovative insights, may clarify favored avenues for research. The primary objective is to present an updated overview of existing information about the processes that precede earthquake occurrence. This information may be utilized to design earthquake forecasting experiments aimed at evaluating their accuracy across various geophysical settings.

Author contributions

GM: Conceptualization, Investigation, Writing – original draft, Writing – review and editing. FH: Writing – original draft, Writing – review and editing. CH: Writing – original draft, Writing – review and editing. YZ: Writing – original draft, Writing – review and editing. FG: Writing – original draft, Writing – review and editing.

Funding

The authors declare that no financial support was received for the research and/or publication of this article.

Acknowledgements

This Research Topic originates from expanding the influence of the annual conference on the China Earthquake Prediction Forum which was co-sponsored by the Earthquake Prediction Committee of the Seismological Society of China and the Department of Monitoring and Prediction of the China Earthquake Administration. The editors wish to thank all the authors who contributed their manuscripts and reviewers who contributed their time and expertise to reviewing the manuscripts.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

The authors declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision.

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Editorial on the Research Topic Faults and earthquakes viewed by networks, monitoring systems and by numerical modelling techniques