pure and applied geophysics最新文献

The complex seismic responses of heterogeneous reservoirs can be related to the fabric structure, pore/microcrack shape, mineral composition and fluid distribution of the rock in situ. The pore structure refers to the geometric shape, size, spatial distribution and interconnectedness of pores, microcracks and throats. It is closely related to the storage space of reservoirs and the spatial distribution of oil/gas. Understanding the pore structure is crucial for the development of processes to increase oil/gas production capacity. Six dolomite samples from the Gaoshiti-Moxi Longwangmiao Formation are sorted out for measurements, and the ultrasonic and seismic attenuation are determined by using the spectral ratio method and the enhanced frequency shift method, respectively. When predicting the pore structure, we assume that the aspect ratio and volume fraction of pores and microcracks correspond to a normal distribution. On this basis, a model with the Voigt–Reuss–Hill average (VRH), differential effective medium (DEM) theory and infinituple-porosity media (IPM) theory is proposed. The acoustic wave responses in terms of reservoir porosity and standard deviation of normal distribution are analyzed, and multiscale 3D rock physics templates (RPT) are created. The calibrations of the templates are performed with the ultrasonic and seismic data, and then the templates are applied to the field data. The results show that the estimated porosity and pore structure (corresponding to the mean aspect ratio and standard deviation of a normal distribution, respectively) are in substantial agreement with the log data and the actual gas production results.

The association of lightning yield per vertical column aerosol of unit cross section (AOD) with relative humidity and rainfall has been investigated using surface observation as well as satellite data for the south-east Indian peninsula, especially Hyderabad and adjacent areas, from 2019 to 2022. For a healthy finding, the study domain area has been separated into three sub-regions: Region R1 (Lat: 17.7–19.5; Lon: 78.5–84.5); R2 (Lat: 15.1–17.5; Lon: 76–80.1); and R3 (Lat: 12.5–15; Lon: 76–80.1). During the investigation, uneven relationship between aerosol and lightning has been found. The relationship between them increases with decreasing latitude (moving towards the south). It has also been found that the yield of lightning per AOD, cloud per AOD, and rainfall increases when relative humidity increases. However, lightning per rainfall is non-linearly associated with relative humidity. Most of the clouds in region R2 have lightning, with or without rain. A regression equation has been investigated that successfully captures the lightning that occurred in the regions R1 and R2.

We analyzed 872 local earthquakes recorded by 18 seismic stations to estimate P-, S-, and coda-wave quality factors for NW Iran, an active seismic and geothermal region in the central part of the Alpine-Himalayan orogeny in western Asia. The calculated frequency-dependent attenuation relations are as follows: Q_p = 38 ± 2 f ^1.00±0.07, Q_s = 79 ± 2 f ^0.90±0.17, and Q_c = 64 ± 1 f ^0.86±0.18 (for a lapse time window length of 50 s). The depth variations of Q_c were investigated by estimating Q_c at five lapse time windows ranging from 30 to 70 s. The Analysis of Q_c in sub-regions surrounding Sahand volcano, Sabalan volcano, and Talesh Mountains indicates that Q_c is increasing with the increase of the lapse times. However, the Q_c values estimated in the areas surrounding the volcanoes are generally lower than those of the Talesh Mountains, confirming a lithospheric contrast between the warm and weak lithosphere of NW Iran and the more rigid South Caspian Basin lithosphere located beneath the Talesh Mountains. The average Q_s/Q_p ratio in NW Iran is > 1.6 at all frequencies, likely due to a high degree of heterogeneities and thermal activities in the crust.

The rise of extreme heat events and increase in heat stress under changing climate has been a major concern in recent periods. The present study has been undertaken to analyze temperature extremes and heat stress patterns over Eastern India during the period 1981–2020 for April, May, and June (AMJ). Six indices namely, Monthly maximum value of daily maximum temperature (TXx), Monthly maximum value of daily minimum temperature (TNx), Monthly minimum value of daily maximum temperature (TXn), Monthly minimum value of daily minimum temperature (TNn), Percentage of days when maximum temperature > 90th percentile (TX90p) and minimum temperature > 90th percentile (TN90p) have been utilized to assess the changes in temperature extremes. Furthermore, three heat stress indices (HSIs) namely, Humidex, Simplified Wet-Bulb Globe Temperature, and Apparent Temperature have been used to estimate and categorize heat stress levels. Mixed results with both increasing and decreasing trends over different parts of the study area have been observed during three months in case of TXx, TXn, TNx, and TNn. During AMJ, there has been amplification in the frequency of TX90p over coastal regions of West Bengal and Odisha in latest decades. Increasing TN90p frequency has been found over Sikkim, Bihar, and North Bengal while it has decreased over Chhattisgarh and Odisha. The frequency of strong heat stress has intensified over Gangetic West Bengal and Bihar during recent decades. Spatial coverage of strong stress has also gradually extended and the area under no stress has decreased during AMJ season.

This study explores the effect of submesoscale topography on baroclinic instability under the quadric shear basic zonal flow is discussed. On the beta plane approximation, the quasi-geostrophic model is used for numerical simulation, and the multiscale model to discuss and verify this problem. A multiscale framework is used to explain the interaction between mesoscale eddies, submesoscale variability, and topographic effects. The multiscale method makes it possible to express the dynamic characteristics of the governing equations with a set of closed systems containing only mesoscale variables. It is found that the interaction between submesoscale topography and baroclinic instability affects some characteristics of mesoscale variability, such as promoting the formation of mesoscale eddies.

and the energy and momentum transport of eddies.

We test a deep learning based denoising autoencoder algorithm on regional and teleseismic seismological and hydroacoustic datasets, which we compile from the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organisation. We focus on stations which can be relevant to investigate North Korean nuclear tests. Denoising of waveform records using autoencoder techniques potentially enables improved signal detection and processing due to lowered signal-to-noise ratios. We train and compare the performance of several different denoising autoencoder models, for short- and long waveform periods, trained on the complete station network as well as on individual stations. We investigate if the denoised waveform signals are useful for seismic source analysis and if they can still be reliably used in downstream analysis for further inferences on the seismic source type, i.e. seismic moment tensor analysis. The declared North Korean nuclear tests are a suitable benchmark test set, as they have extensively been researched and their source type and location might be assumed known. Verification of the source type is of particular interest for potential nuclear tests under international law. We find that care needs to be taken using the denoised waveform data, as a slight bias is introduced in the seismic moment tensor analysis. However we also find promising results hinting at possible future use of the technique for standard analyses, as it improves the investigation of smaller events. Autoencoder based denoising techniques could be employed in future routine frameworks to increase earthquake catalog completeness and possibly aid in detecting smaller potential treaty relevant events.