pure and applied geophysics最新文献

Frictional sliding along grain boundaries in brittle shear zones can result in the fragmentation of individual grains, which ultimately can impact slip dynamics. During deformation at small scales, stick–slip motion can occur between grains when existing force chains break due to grain rearrangement or failure, resulting in frictional sliding of granular material. The rearrangement of the grains leads to dilation of the granular package, reducing the shear stress and subsequently leading to slip. Here, we conduct physical experiments employing HydroOrbs, an elasto-plastic material, to investigate grain comminution in granular media under simple shear conditions. Our findings demonstrate that the degree of grain comminution is dependent on both the normal force and the size of the grains. Using the experimental setup, we benchmark Discrete Element Method (DEM) numerical models, which are capable of simulating the movement, rotation, and fracturing of elasto-plastic grains subjected to simple shear. The DEM models successfully replicate both grain comminution patterns and horizontal force fluctuations observed in our physical experiments. They show that increasing normal forces correlate with higher horizontal forces and more fractured grains. The ability of our DEM models to accurately reproduce experimental results opens up new avenues for investigating various parameter spaces that may not be accessible through traditional laboratory experiments, for example, in assessing how internal friction or cohesion affect deformation in granular systems.

In order to seismically characterize Chile’s northern Coquimbo Region, data from 2003 to 2020 were considered. The region was divided into 30 zones of (0.5^circ) latitude and (0.5^circ) longitude and non-extensive statistical physics was used. Both, the Sotolongo–Costa–Posadas (SCP) and Mathai models were deployed to analyze the magnitude-frequency distribution. A sub-division into cells of the catalog allowed to demonstrate that systems with value of (q sim 1) present exponential behavior, while it was expected to obtain (q > 1), by superimposing sub-systems supporting the superstatistical model. Thus, by subdividing the Coquimbo region into south and north, we found that in both zones the entropic index is greater than 1, (q>1), However, in the southern zone the long-range effects are greater than in the north, according to the value obtained, which means both sectors are well described under a nonextensive statistical model, be it the SCP model or the Mathai one. The entropic index is (q>1) and in both cases (R^2>0.99). As the region is considered as a whole, the nonextensive statistical distribution is the more adequate one. With respect to probabilistic seismic hazard assessment, Mathai’s model proved to have the better fit. Thus, the frequency-interevent time distribution was used for different limit magnitude values. Our analysis showed that the probability occurrence of a seismic event in the region’s north is lower than in the south considering the same period. In the north the behavior is of Poissonian type.

Traces of past landslides were found on the seabed of Palabuhanratu Bay, West Java. This landslide is thought to have generated a tsunami, but has never been investigated before. This bay is located around the western part of the Cimandiri Fault which is an active horizontal fault with a length of 100 km. Therefore, it is necessary to study the potential impact of a tsunami in the Palabuhanratu Bay area caused by a combination of local earthquakes and underwater landslides around the bay. Evidence of past landslides was revealed through side-scan sonar data from the underwater research vessel Baruna Jaya IV in Palabuhanratu Bay, Indonesia, in 2020. The data from this survey provides evidence of debris flows (historical landslide data) at the survey site. We simulated 29 tsunami scenarios from combined landslide earthquake sources by solving shallow water nonlinear equations numerically. Tsunami sources from earthquakes are classified into three types, e.g., land faults, sea faults, and combinations of land and sea faults. While the source of the tsunami from the landslide is divided by volume. Combination of the earthquake magnitudes range from M6.80 to M7.85, and the landslide volume ranged from 3.06 × 10⁵ m³ to 2.5 × 10⁸ m³. This study concludes that in our scenario, the M8.12 type T7 earthquake generates the largest tsunami in the study area, followed by the T6L5 scenario with M7.85 from the Cimandiri Fault and landslide with a total volume of 2.5 × 10⁸ m³.

The tropopause serves a critical role in shaping global and regional weather and climate dynamics. Changes in tropopause characteristics can significantly impact other atmospheric components, thereby influencing Earth’s climate systems. In the long run, variations in tropopause features can lead to shifts in the thermal, dynamic, and chemical properties of the tropospheric layer. This study aims to investigate the descriptive attributes of tropopause pressure levels (TPLs) during different months, as well as the temporal and spatial trends in TPL across the Northern Hemisphere spanning from 1979 to 2022. Utilizing ERA5 temperature data for the 700 to 50 hPa range, the tropopause was identified using the lapse rate of tropopause (LRT), and its changes were analyzed employing the linear regression model with the least squares error approach. The results indicated that the spatial pattern of TPLs changed across various latitudes varies seasonally. Generally, the changes in TPLs did not exhibit a linear relationship with latitude, and in most observed months, the highest and lowest TPLs did not correspond to the lowest and highest latitudes, respectively. Examination of the trend in TPLs revealed that in numerous significant areas across different seasons, the trends were statistically insignificant. Where significant, the trends predominantly indicated negative changes (decreases), suggesting a reduction in pressure and potentially an increase in tropopause altitude in these regions, possibly reflecting the influence of global warming.

In this paper, a two-dimensional numerical model for simulating the generation and propagation of tsunami waves caused by upthrust bed movement is developed. To consider the nonlinearity as well as save the computational cost, a Navier–Stokes equation solver is used for the generation zone, and a Serre equation solver is adopted for the downstream evolution of the tsunami waves. The solution of the Navier–Stokes equation solver is extracted and transferred as the initial solution of the Serre solver, which means a one-way coupling is achieved. In this way, a one-way coupled Navier–Stokes-Serre model is obtained. After a detailed validation of the individual solvers, the coupled model is utilized for simulating the generation and propagation of tsunami waves caused by the upthrust bed movement in shallow water of uniform depth. It is found that the coupled model is comparable to the traditional Boussinesq equation model. Finally, the capacity of the coupled model for simulating wave-breaking cases is demonstrated.

Tsunamis generated by the Hunga Tonga–Hunga Ha’apai volcanic eruption on January 15, 2022 were recorded on ocean bottom pressure and tide gauges around the Pacific Ocean, earlier than the expected arrival times calculated by tsunami propagation speed. Atmospheric waves from the eruption were also recorded globally with propagation speeds of ~ 310 m/s (Lamb wave) and 200–250 m/s (Pekeris wave). Previous studies have suggested that these propagating atmospheric waves caused at least the initial part of the observed tsunami. We simulated the tsunamis generated by the propagation of the Lamb and Pekeris waves by adding concentric atmospheric pressure changes. The concentric sources are parameterized by their propagation speeds, initial atmospheric wave amplitudes that decay with the distance, and a rise time. For the Lamb wave, inversions of the observed tsunami waveforms at 14 U.S. and nine New Zealand DART stations indicate the start of the positive rise at 4:16 UTC, the peak amplitude of 383 hPa, and the propagation speed of 310 m/s, assuming a rise time of 10 min. The later phases of the observed tsunami waveforms can be better reproduced by adding another propagating concentric wave (Pekeris wave) with a negative amplitude (− 50 hPa) and propagation speeds of 200–250 m/s. The DART records around the Pacific indicate that the Pekeris wave speed is faster toward the northwest and slightly slower toward the northeast. The synthetic waveforms roughly reproduced the far-field tsunami waveforms recorded at tide gauge stations, including the later phases, suggesting that the large amplitude in the later phase may be due to the coupling of the Pekeris wave and the tsunami, as well as resonance around tide gauge stations.

The movement of the Earth's surface mass, including the atmosphere and oceans, as well as hydrology and glacier melting, causes the redistribution of surface loads, deformation of the solid Earth, and fluctuations in the gravity field. Global Navigation Satellite Systems (GNSS) provide useful information about the movement of the Earth's surface mass. The impact of surface loading deformation over 145 GNSS sites in Africa was investigated using vertical height time series analysis. The study investigates and quantifies the impact of surface loading on the GNSS coordinates utilizing GNSS Precise Point Positioning (PPP) approach. The German Research Center for Geosciences (GFZ) EPOS.P8 software was used to process and analyze eleven years of GPS data from all the stations, as well as dedicated hydrological and atmospheric loading correction models given by the Earth System Modeling group at Deutsches GeoForschungsZentrum (ESMGFZ). The results of the hydrological loading corrections arising from the surface-deformation were analysed to determine the extent of station improvements. The results revealed about 40% of the stations showed improvement with an average Root Mean Square Error (RMSE) residual of 7.3 mm before the application of the hydrological loading corrections and 7.1 mm Root Mean Square Error (RMSE) after the application of the hydrological loading corrections. Similarly, the atmospheric loading corrections gave an improvement of about 57%. Furthermore, the amplitude values decreased from 4.1–8.1 mm to 3.5–6.2 mm after atmospheric loading corrections. This finding presupposes that applying loading corrections to the derived time series reduces amplitude in some African regions.

The free-air gravity anomaly along the Aleutian subduction zone exhibits a single set of negative and positive trench-parallel belts in the western region, whereas it exhibits doubled negative–positive trench-parallel belts in the eastern region. The eastern inner–western positive gravitational belt corresponds to the topographic chain of the Alaska Peninsula and the Aleutian Islands. However, the eastern outer positive gravitational belt does not coincide with the chain of the topographic outer-arc highs. In this study, we determined the across-trench profiles of the plate interface geometry for the western and eastern Aleutian subduction zones on the basis of the hypocentre distribution. The surface uplift rates computed from the dislocation-based two-dimensional subduction model for the Aleutian plate interface profiles adequately reproduced the western single-arc and eastern double-arc characteristics. The essential factors of the double-arc formation are a low subduction dip angle and a bimodal plate interface curvature distribution within the elastic lithosphere. The double-arc highs of the computed uplift rates more closely coincided with the gravitational highs than the current topographic highs. This implies that tectonic events in the past caused the topographic activity shift towards the continental shelf edge and the subsequent topographic readjustment under the current tectonic state.

In this study, the atmospheric changes for the 9.0-magnitude Tohoku earthquake, which occurred on March 11, 2011, are analyzed. The March 11, 2011 earthquake was preceded by a large foreshock on March 09, 2011 with magnitude M 7.3 and depth 32 km at 02:45:20 UT near the east coast of Honshu, Japan. The earthquake doesn’t limit its effects on the Earth’s lithosphere, hydrosphere and biosphere; it also extends its effects to the atmosphere because of the gas emissions, which produce large-scale seismic waves from the ground and release gases into the atmosphere. In this study, the anomalies of the atmospheric parameters are studied by using one of the atmospheric models from the Naval Research Laboratory Mass Spectrometer Incoherent Scatter Extension 2000 (NRLMSISE-00) model data to analyze the atmospheric anomalies of the Tohoku Earthquake on March 11, 2011. The atmospheric parameters of atomic oxygen (O), hydrogen (H), atomic nitrogen (N), helium (He), argon (Ar), molecular oxygen (O₂), molecular nitrogen (N₂), total mass density (ρ), neutral temperature (Tn), exospheric temperature (Tex) and anomalous oxygen (AO) are used for analysis during the earthquake occurrence. The epicenter of the Tohoku earthquake, with a geographical location of latitude 38.30° N and longitude 142.37° E, is used for the NRLMSISE-00 model as input parameters to analyze the output of atmospheric parameters. To compare the atmospheric changes caused by the earthquake, 5 days before and after the earthquake are considered. To detect where the atmospheric parameters increased or decreased from the earthquake day, the percentage deviation of the NRLMSISE-00 model is applied. The results indicate that there were atmospheric parameter anomalies that occurred a few days before, following and during the earthquake on March 11, 2011. Except for hydrogen (H), all atmospheric parameters average daily percentage deviation values were positive during the 5 days before and after with respect to the main earthquake shock on March 11, 2011. The NRLMSISE-00 model can capture the atmospheric parameter anomalies of the Tohoku earthquake well.