Earthquake-related Phenomena Research Articles

Applying support vector machine (SVM) using GPS-TEC and Space Weather parameters to distinguish ionospheric disturbances possibly related to earthquakes

The effort to identify and comprehend potential earthquake-related phenomena shares a common goal: successful earthquake forecasting. Advancements in science and technology have made this goal multidisciplinary. Currently, possibly earthquake-related anomalies in the Vertical Total Electron Content (VTEC) of the Earth’s ionosphere are being investigated. Global Navigation Satellite Systems (GNSS) can be used to calculate this ionospheric parameter. In this research work, GPS VTEC was calculated for periods between the years 2015 and 2019. The selection of this periods considered both seismically active and non-seismically areas in Mexico. The Mw ≥ 5 earthquakes under study were registered by the National Seismological Service. Moreover, different geomagnetic storm and solar activity parameters, such as the geomagnetic equatorial Dst index and the F10.7 index, were analyzed. Additionally, the daily average and monthly mean number of sunspots (R, SSN, respectively) were included as a direct, long-term record of the development of the solar cycle. To the periods under study different statistical methods were applied, such as Mean-Square Error (MSE) and cross-correlation. The above aims to apply a machine learning technique capable of classifying between periods with seismic and non-seismic activity. The features were constructed using statistical data and results from the implemented analysis. Furthermore, Principal Component Analysis (PCA) was applied to reduce the feature vector dimensions, and accuracy scores were compute using k-fold cross-validation. The results from the Support Vector Machine (SVM) model indicated an accuracy of 88.9% for the training set, and an accuracy of 80% was obtained for the test set. One of the limitations of the current study was the sample size. However, the present initial approach for classifying seismic events from non-seismic periods using SVM demonstrated promising results when considering the indicated parameters and the days under study.

Multiple seismo-anomalies associated with the M6.1 Ludian earthquake on August 3, 2014

Multiple geophysical parameters including groundwater level, water temperature, water radon, crustal deformation, electromagnetic waves and total electron contents (TEC) in the ionosphere, are examined together to investigate pre-earthquake anomalous phenomena associated with the Mw6.1 Ludian earthquake on August 3, 2014. Cross-parameter comparison eliminates anomalies that are detected in one parameter only and examine earthquake-related phenomena in various fields, simultaneously. Retrieved anomalies show that abnormal decreases of water temperature and radon concentration related to anomalous uplift of groundwater levels appeared about 1–8days before the earthquake even without contributions from rain. Significant step-like changes are observed from data recorded by strainmeters on July 31 and are consistent with water-related anomalies in timing. No significant anomalies can be found from electromagnetic data through the preliminary observation. In contrast, TEC appeared positive anomalies 1–3days before the Ludian earthquake. Although causal mechanisms of the TEC anomalies from stressed rocks are not fully understood, multiple-parameter examination can increase credibility of determination regarding pre-earthquake phenomena.

Preface to the special issue on seismoelectromagnetics: Earthquake-related phenomena, laboratory evidences and their mechanism

Preface to the special issue on seismoelectromagnetics: Earthquake-related phenomena, laboratory evidences and their mechanism

S. E. Hough 2007. Richter's Scale. Measure of an Earthquake, Measure of a Man. xiii + 337 pp. Princeton, Oxford: Princeton University Press. Price £17.95, US $27.95 (hard covers). ISBN 9780 691 12807 8.

S. E. Hough 2007. Richter's Scale. Measure of an Earthquake, Measure of a Man. xiii + 337 pp. Princeton, Oxford: Princeton University Press. Price £17.95, US $27.95 (hard covers). ISBN 9780 691 12807 8. - Volume 144 Issue 6

Experimental frictional heating of coal gouge at seismic slip rates: Evidence for devolatilization and thermal pressurization of gouge fluids

High velocity (1 m/s) friction experiments on bituminous coal gouge display several earthquake-related phenomena, including devolatilization by frictional heating, gas pressurization, and slip weakening. Stage I is characterized by sample shortening and reduction in the coefficient of friction ( μ) from ∼ 1 to 0.6. Stage II is characterized by high frequency (∼ 5 Hz) oscillations in stress and strain records and by gas emissions. Stage III is marked by rapid weakening ( μ ∼ 0.1 to 0.35) and sample shortening, together with continued gas emissions. Stage IV produces stable stress records and continued weakness ( μ ∼ 0.2), but without gas emission. Stage I shortening is due to compaction of the gouge and the weakening is attributed to mechanical or thermal effects. Stage II behavior is interpreted as due to coal gasification and fluctuations in fluid pressure, resulting in high frequency stick-slip type behavior. Dramatic reduction in shear stress in stage III is attributed to gas pressurization by pore collapse and corresponds to a frictional instability, analogous to nucleation of an earthquake. Microstructural observations indicate the deformation was brittle during stages I and II but ductile during stages III and IV. Time dependent finite element frictional heat models indicate the center of the samples became hot (∼ 900 °C) during stage II, whereas the edge of samples remained relatively cold (< 300 °C). Vitrinite reflectance of coal samples shows an increase in reflectance from ∼ 0.5 to ∼ 0.8% over the displacement interval 20–40 m (20–40 s), indicating that the reflectance responds to frictional heating on a short time scale. The energy expended per unit area in these low stress, large displacement experiments is similar to that of higher stress (∼ 50 MPa), short displacement (∼ 1 m) earthquakes (∼ 10 7 J/m 2).

EARTHQUAKES, OIL, AND WATER DON'T MIX

ABSTRACT The release of crude oil into a southern California river from an earthquake-related pipeline rupture resulted in an initial rise in TPH and total BTEX concentrations in the water column. No toxicity was observed in aquatic toxicity tests conducted with rainbow trout and threespine stickleback. Statistically significant differences noted in several of the indices of macroinvertebrate community structure at sites downstream from the oil entry location appeared to be due to confounding factors including the spill. The assessment of incident-related impacts was complicated by several earthquake-related phenomena.

Well-level variation as a possible seismic precursor: a statistical assessment from Italian historical data

Abstract A large data set on earthquake-related phenomena was collected in Italy during the last century. In this paper we consider the well-level measurements sampled with a daily frequency over a decade by D. Lorenzini in Porretta (near Bologna, Italy). These data were collected independently of earthquake occurrences and are important because of the absence of noise in groundwater levels due to anthropogenic activity (such as reservoir filling, fluid injection or extraction). Furthermore, atmospheric-pressure recordings are available as well as (partly) those of rainfall. A statistical analysis of this kind of precursor is performed, taking into account the daily variations in well levels after removing the autocorrelation effects, and looking for correlations with atmospheric pressure. In this way it is possible to determine a set of outliers considered as anomalous and then to match them with the occurrence of earthquakes and rainfall. Some of the outliers seemed to be related to intense rainfall, and for this reason the historical and statistical approach was completed with a local hydrogeological study. The results obtained when rainfall effects are taken into account, show a significant interrelation between local seismic activity and well-level anomalies, probably related to the peculiar behaviour of the local deep geothermie reservoir. These results are encouraging for further historical research to provide a broader data base and to eliminate the incompleteness that is still a disadvantage of the Italian Earthquake Catalogue.