Tectonic hydrogen and tectonic oxygen production through deforming piezoelectric minerals in the presence of water

ABSTRACT A high concentration of hydrogen gas occurs in fracture zones of active faults that are associated with historical earthquakes. To explain the described phenomenon, we propose the piezoelectrochemical (PZEC) effect as a mechanism for the direct conversion of mechanical energy to chemical energy. When applied to natural piezoelectric crystals including quartz and serpentine, hydrogen and oxygen are generated via direct water decomposition. Laboratory experiments show H2 gas is generated from strained piezoelectric material due to the extremely low solubility of H2, suggesting that the deformed or strained mineral surfaces can catalyze water decomposition. If the strain-induced H2 production is significant, hydrogen measurements at monitoring sites can offer information on deformation of rocks operating at depth prior to earthquakes. Oxygen can be measured in water due to its high solubility compared to hydrogen. Our experimental results demonstrate that dissolved oxygen generated from the PZEC effect can oxidize dissolved organic dye and ferrous iron in an aqueous Fe(II)–silicate metal complex. The hydrogen and oxygen formed through stoichiometric decomposition of water in the presence of strained or deformed minerals in fault zones (including subduction zones and transform faults) may be referred to as tectonic hydrogen and tectonic oxygen. Tectonic hydrogen could be a potential energy source for deep subsurface and glacier-bedrock interface microbial communities that rely on molecular hydrogen for metabolism. Tectonic oxygen may have been an important oxidizing agent when dissolved in water during times in early Earth history when atmospheric oxygen levels were extremely low. Reported “whiffs” of dissolved oxygen before the Great Oxidation Event might have been related to tectonic activity.

Time difference between the 1854 CE Ansei–Tokai and Ansei–Nankai earthquakes estimated from distant tsunami waveforms on the west coast of North America

We estimated the time difference between the 1854 CE Ansei–Tokai and Ansei–Nankai earthquakes from tidal records of two tide gauge stations (San Francisco and San Diego) on the west coast of North America. The first signals of the Ansei–Tokai tsunami were apparent, whereas those of the Ansei–Nankai tsunami were obscured by the later waves of the Ansei–Tokai tsunami. Waveforms of the Ansei–Nankai tsunami simulated with nonlinear dispersive wave theory by assuming an origin time of 07:00 GMT on 24 December arrived earlier than in the observations. The normalized root mean square and the misfit between the simulated and observed waveforms of the Ansei–Nankai tsunami showed a time difference between them of approximately 0.4 h. This finding suggests that the actual origin time of the Ansei–Nankai tsunami was approximately 07:24 GMT on 24 December. A previous study estimated the origin time of the Ansei–Tokai tsunami to be about 00:30 GMT on 23 December. Thus, we concluded that the time difference between the 1854 CE Ansei–Tokai and Ansei–Nankai tsunamis was 30.9 h. Despite the significant difference in the time resolution between the seasonal timekeeping system used in Japan in 1854 and waveform digitization, our result is roughly in agreement with historical descriptions of the tsunamis, suggesting that such information can be effectively used to determine the origin times of historical earthquakes.

Interplay of Holocene surface faulting and climate in the Central Po Plain, Italy

Understanding the recent events marking the late Quaternary history of the Po Plain (N-Italy) is of overriding importance to decipher the record of depositional versus erosional phases, and their interplay with climatic, tectonic, and human forcing. We reconstructed the structural setting and chronostratigraphy of a Holocene succession crosscut by a thrust fault located south of Montodine (Cremona, Italy) within the Po Plain. The fault shows a maximum displacement up to one meter. Radiocarbon dating fixes a minimum age of 11.9 cal ka BP for the postglacial river entrenchment and constrains the fault movement age between 5.9 and 3.4 cal ka BP. Undeformed Late Medieval coarse gravels cover the faulted succession. Due to the outcrop position, lying above the buried frontal thrusts of the Southern Alps and North Apennines, we propose that faulting results from secondary surface effects induced by seismic shaking. We discuss two main mechanisms, both related to lateral spreading, that can result in the formation of reverse faults close to the surface. The Soncino area, recording one of the strongest historical earthquakes of the central Po Plain (1802), is considered as a possible source for seismic shaking. The results of this study are a contribution for the assessment of the potential seismic hazard in one of the most populated regions of Europe.

A Zoning Earthquake Casualty Prediction Model Based on Machine Learning

The evaluation of mortality in earthquake-stricken areas is vital for the emergency response during rescue operations. Hence, an effective and universal approach for accurately predicting the number of casualties due to an earthquake is needed. To obtain a precise casualty prediction method that can be applied to regions with different geographical environments, a spatial division method based on regional differences and a zoning casualty prediction method based on support vector regression (SVR) are proposed in this study. This study comprises three parts: (1) evaluating the importance of influential features on seismic fatality based on random forest to select indicators for the prediction model; (2) dividing the study area into different grades of risk zones with a strata fault line dataset and WorldPop population dataset; and (3) developing a zoning support vector regression model (Z-SVR) with optimal parameters that is suitable for different risk areas. We selected 30 historical earthquakes that occurred in China’s mainland from 1950 to 2017 to examine the prediction performance of Z-SVR and compared its performance with those of other widely used machine learning methods. The results show that Z-SVR outperformed the other machine learning methods and can further enhance the accuracy of casualty prediction.

Fault Geometry and Mechanism of the Mw 5.7 Nakchu Earthquake in Tibet Inferred from InSAR Observations and Stress Measurements

Different types of focal mechanism solutions for the 19 March 2021 Mw 5.7 Nakchu earthquake, Tibet, limit our understanding of this earthquake’s seismogenic mechanism and geodynamic process. In this study, the coseismic deformation field was determined and the geometric parameters of the seismogenic fault were inverted via Interferometric Synthetic Aperture Radar (InSAR) processing of Sentinel-1 data. The inversion results show that the focal mechanism solutions of the Nakchu earthquake are 237°/69°/−70° (strike/dip/rake), indicating that the seismogenic fault is a NEE-trending, NW-dipping fault dominated by the normal faulting with minor sinistral strike-slip components. The regional tectonic stress field derived from the in-situ stress measurements shows that the orientation of maximum principal compressive stress around the epicenter of the Nakchu earthquake is NNE, subparallel to the fault strike, which controlled the dominant normal faulting. The occurrence of seven M ≥ 7.0 historical earthquakes since the M 7.0 Shenza earthquake in 1934 caused a stress increase of 1.16 × 105 Pa at the hypocenter, which significantly advanced the occurrence of the Nakchu earthquake. Based on a comprehensive analysis of stress fields and focal mechanisms of the Nakchu earthquake, we propose that the dominated normal faulting occurs to accommodate the NE-trending compression of the Indian Plate to the Eurasian Plate and the strong historical earthquakes hastened the process. These results provide a theoretical basis for understanding the geometry and mechanics of the seismogenic fault that produced the Nakchu earthquake.

A Perspective of historical earthquakes in India and its neighbourhood upto 1900

A study has been carried out on past seismic activity in India and its neighbourhood from ancient times to nineteenth century, During sixth century AD, the great Indian astronomer Varaha Mihira investigated earthquakes in his book 'Brihat Samhita', A brief description and analysis on his investigations have been cited, Based on scientific reports and a few history and geography books, a list of earthquakes of magnitude 6 and above upto 1900 AD has been prepared for India and its neighbourhood in the region bounded by latitude between 0° and 40° N and longitude between 60°E and 100°E, A brief description of earthquakes of magnitude 8 and above has also been included.

Evaluating landslide response in a seismic and rainfall regime: a case study from the SE Carpathians, Romania

There have been many studies exploring rainfall-induced slope failures in earthquake-affected terrain. However, studies evaluating the potential effects of both landslide-triggering factors – rainfall and earthquakes – have been infrequent despite rising global landslide mortality risk. The SE Carpathians, which have been subjected to many large historical earthquakes and changing climate thus resulting in frequent landslides, comprise one such region that has been little explored in this context. Therefore, a massive (∼9.1 Mm2) landslide, situated along the river Bâsca Rozilei, in the Vrancea seismic zone, SE Carpathians, is chosen as a case study area to achieve the aforesaid objective (evaluating the effects of both rainfall and earthquakes on landslides) using slope stability evaluation and runout simulation. The present state of the slope reveals a factor of safety in a range of 1.17–1.32 with a static condition displacement of 0.4–4 m that reaches up to 8–60 m under dynamic (earthquake) conditions. The groundwater (GW) effect further decreases the factor of safety and increases the displacement. Ground motion amplification enhances the possibility of slope surface deformation and displacements. The debris flow prediction, implying the excessive rainfall effect, reveals a flow having a 9.0–26.0 m height and 2.1–3.0 m s−1 velocity along the river channel. The predicted extent of potential debris flow is found to follow the trails possibly created by previous debris flow and/or slide events.

THE RESIZING OF THE MOST POWERFUL ITALIAN INSTRUMENTAL EARTHQUAKE (SEPTEMBER 8, 1905, CALABRIA REGION, SOUTHERN ITALY)

The 8 September 1905 Calabria earthquake is the seismic event for which the Italian Seismic Catalogue shows the highest instrumental magnitude of the whole dataset. However, the reported Ms=7.47 was calculated over only two stations, and leaves room for a revision. In this work I provide a new estimate of the surface-wave magnitude of the earthquake calculated over sixteen individual values of magnitude from seven different stations. The new estimate is Ms=7.06±0.13, a value that is consistently lined up with other estimates provided by means of macroseismic or geological evidence. The novel estimate is stable despite alternative epicentral locations and different depths proposed for this event by several investigators. The net variation of almost half a unit magnitude implies a resizing of the seismogenic source of the event in the frame of the seismotectonics of the region, and highlights the strong need for a systematic revision of the instrumental magnitude estimates for several ‘historical’ earthquakes that occurred at the dawning of the instrumental seismology.