by Daniela Dalla Chiesa, Letícia Fleck Fadel Miguel, Jorge Daniel Riera,
31 May, 2022
A numerical procedure, based on an evolutionary optimization algorithm, has been proposed by the authors for the simultaneous generation of the three components of the seismic ground acceleration. The methodology allows the determination of a train of seismic waves modeled by three different waveforms, for the generation of ground seismic acceleration components. The parameters of each wave, i.e., amplitude, frequency, duration, arrival time and direction, are determined using an evolutionary optimization algorithm. Although no theoretical justification is known by the authors for the generation, at the seismic source, of specific initial waveforms, both in case of fracture or of sliding with friction, waveform acceleration components that satisfy the condition of zero final velocity should in principle be preferred. The latter is a physical restriction that is automatically satisfied by anti-symmetrical functions, thus eliminating the need to correct the baseline of simulated accelerograms. The error of fit of simulated accelerograms generated by three different waveforms proposed in the literature was herein determined by comparison with actual seismic records. On that basis, estimations of the expected error of the evolutionary optimization algorithm in engineering applications are presented.
A suitable combination of magnetic field determinations is assembled in the whole area of the Jalisco block in central-western Mexico; it serves as the basis for calculations of the Curie Point Isotherm by means of Spectral Analysis. The Jalisco block contains numerous volcanic manifestations; an attempt is made at correlating the Curie Isotherm (CI) with volcanic manifestations and its implicit risk to nearby populated regions. A preliminary analysis of this isotherm is carried out using areas of 60 × 60 km2 , where the volcanic regions at the NW and SE portions of the Tepic-Zacoalco (TZ) rift coincide with shallow layers of the CI. Results show an unexpected region in the middle of the T-Z rift, where the isotherm deepens to 12 km depth and volcanism appears to be missing. The authors argue that this phenomenon may be associated with a flare up episode occurring at 5-3 Ma along the rift. Varying the area used for the calculation of the CI, from 30 × 30 km2 to 120 × 120 km2 , illustrates how the concomitant changes in volume affect the depth of penetration. The authors find exceptional regions in which the CI shows shallow depths at all area sizes used in the calculations; this consistency is interpreted as a magnetic alteration of the crust originating at mid-crustal depths. These regions also correspond to high values of the Bouguer anomaly reported elsewhere. Six magneto-stratigraphic profiles are presented for the results of the 60 × 60 km2 calculations, where geologic, topographic, and magnetic properties are displayed along their length.
by R. Sharbati, Hamidreza Amindavar, H. R. Ramazi, S. Foti, B. Farzanegan,
31 May, 2022
This article proposes a stochastic model for generation of synthetic seismic ground motions. In the first step, the wavelet coefficients of a record are extracted by the dual-tree complex discrete wavelet transform (DT-CDWT) and then they are simulated by an optimized Cauchy-Gaussian blend (CGB) model. This model predicts well the energy distribution of seismic ground motions, because in this model, the Gaussian distribution simulates smooth peaks and the Cauchy distribution is used to simulate impulsive peaks. Also, this model simulates several ascending-descending cycles in the time domain, predicts multiple frequency peaks each time, and simulates sequence-type records.
Well-coordinated efforts are being made in dishing out meteorological services by the Nigerian Meteorological Agency to ensure the delivery of timely, accurate and quality weather information for the development of agricultural activities in the drylands of Nigeria for sustainable food security. This is through the densification of the observations networks, acquisition of the relevant and latest weather instruments and improvement in weather equipment and training of technical data capturing system, data delivery system, calibration of equipment, installation, routine maintenance of the equipment and training and retraining of staff .This work is aimed at giving an insight to the efforts being made by NIMET towards the issuance of accurate weather information for agricultural development. The information contained in Seasonal Rainfall Prediction (SRP), 2019 and 2020 is given consideration in this study especially as it relates to agriculture for food security in the drylands of Nigeria