Phys.org September 13, 2024 In subduction zones, water expelled from the subducting slab is believed to be involved in seismic activity. However, little is known about its quantity and flow processes. Researchers in Japan showed that the Arima hot springs in western Japan contained high concentrations of water derived from the subducting Philippine Sea slab. A long-term record spanning over half a century revealed that the fraction of slab-derived water exhibited a temporary surge in the year preceding and/or subsequent years of the 1995 Kobe earthquake. In total, an estimated 2.6–4.2 × 105 cubic meters of slab-derived water was introduced in conjunction […]
Category Archives: Earthquakes
Electricity generated by earthquakes might be the secret behind giant gold nuggets
Phys.org September 2, 2024 Gold nuggets occur predominantly in quartz veins, and the current paradigm posits that gold precipitates from dilute (<1 mg kg−1 gold), hot, water ± carbon dioxide-rich fluids owing to changes in temperature, pressure and/or fluid chemistry. However, the widespread occurrence of large gold nuggets is at odds with the dilute nature of these fluids and the chemical inertness of quartz. Using quartz deformation experiments and piezoelectric modelling researchers in Australia investigated if piezoelectric discharge from quartz could explain the ubiquitous gold–quartz association and the formation of gold nuggets. They found that stress on quartz crystals could generate enough voltage to […]
Geophysicists find link between seismic waves called PKP precursors and strange anomalies in Earth’s mantle
Phys.org August 17, 2024 Seismic energy arriving before the compressional (P) wave passing through the core (PKP), called PKP precursors, have been detected for decades, but the origin of those arrivals is ambiguous. The largest amplitude arrivals are linked to scattering at small-scale lowermost mantle structure, but because these arrivals traverse both source and receiver sides of the mantle, it is unknown which side of the path the energy is scattered from. To address this ambiguity, an international team of researchers (USA – University of Utah, University of Arizona, UK) applied a new seismic array method to analyze PKP waveforms […]
Neural networks could help predict destructive earthquakes
Phys.org March 3, 2023 The movement and deformation of the Earth’s crust and upper mantle provide critical insights into the evolution of earthquake processes and future earthquake potentials. Crustal deformation can be modeled by dislocation models that represent earthquake faults in the crust as defects in a continuum medium. Researchers in Japan have proposed a physics-informed deep learning approach to model crustal deformation due to earthquakes. Neural networks can represent continuous displacement fields in arbitrary geometrical structures and mechanical properties of rocks by incorporating governing equations and boundary conditions into a loss function. They introduced polar coordinate system to accurately […]
California Quakes Mysteriously Preceded by Shifts in Earth’s Magnetic Field
Science Alert October 10, 2022 Magnetic field changes as earthquake precursors have been the subject of numerous studies and some controversy. Infrequent large earthquakes and sparse magnetometer coverage along fault zones complicate statistical analysis. A team of researchers in the US (Google Research, industry) analyzed ground-based magnetic time-series measurements before 19 earthquakes in California drawing from over 330,000 site-days of measurement spanning a decade. They applied a pre-specified statistical analysis with two key ideas – combining signals from nearby sites via spectral cross-power, and then looking for large spikes in frequency domain 0.016–25 Hz. They used the machine learning concept […]
Months of gravity changes preceded the Tōhoku earthquake
Phys.org September 1, 2022 Researchers in France conducted a global analysis of Gravity Recovery and Climate Experiment (GRACE) reconstructed gravity gradients from July 2004 to February 2011 to test whether the deep signals preceding the March 2011 Tohoku earthquake could be detected before the event as a specific feature originating from solid Earth. They improved the angular resolution of the gravity gradients using two overlapping ranges of azimuthal sensitivity to investigate short-term signals of large amplitude aligned with the orientation of the Northwestern Pacific subduction and set-up a method to identify consistent solid Earth signals shared by different GRACE gravity […]
Hidden magnitude-8.2 earthquake source of mysterious 2021 global tsunami
Phys.org February 8, 2022 The 2021 August South Sandwich Island Mw 8.2 earthquake was a surprise, because it was initially reported as a magnitude 7.5 event at a deep depth (47 km) but generated a global-spreading tsunami that would only be expected for a larger and shallower event. By using seismic data researchers at Caltech revealed a hidden Mw 8.16 shallow slow event that happened between clusters of regular ruptures in the beginning and end. Although the slow event contributed 70% of the seismic moment, lasted three minutes, and ruptured a 200-km section of the plate interface, it is essentially […]
New type of earthquake discovered
Phys.org December 6, 2021 A seismic slip loading has recently been proposed as a complementary mechanism to induce moderate-sized earthquakes located within a few kilometers of the wellbore over the timescales of hydraulic stimulation. However, aseismic slip signals linked to injection-induced earthquakes remain largely undocumented to date. An international team of researchers (Canada, Germany) has reported a new type of earthquake characterized by hybrid-frequency waveforms (EHWs). Distinguishing features from typical induced earthquakes include broader P and S-pulses and relatively lower-frequency coda content. Both features may be causally related to lower corner frequencies, implying longer source durations, thus, either slower rupture […]
Keeping one step ahead of earthquakes
Phys.org November 3, 2021 According to the researchers in France AI has the potential to improve the accuracy and speed of early warning systems. Earthquake early warning (EEW) systems are evolving rapidly due to advances in computer power and network communication. They work by identifying the first signals generated by an earthquake rupture before the strongest shaking and tsunami reach populated areas. These signals follow the origin of the earthquake and can be recorded seconds before the seismic waves. Prompt elasto-gravity signal (PEGS) which was recently identified travels at the speed of light but is a million times smaller than […]
Anatomy of an earthquake series
Science Daily August 11, 2021 Gas storage oil field operations worldwide are typically not stimulating substantial seismicity. However, the Castor sequence in Spain remains to date the most significant case of seismicity related to this type of industrial operations in Europe. The new analysis by an international team of researchers (Germany, Spain, Italy, Switzerland, USA- Stanford University) identified about 3,500 earthquakes, which took place at shallow depth between September and early October in the vicinity of the Castor injection platform using a combination of advanced seismological techniques applied to an enhanced waveform dataset to better understand the seismogenic process and […]