Short Wavelength Components Research Articles

Authentic fault models and dispersive tsunami simulations for outer-rise normal earthquakes in the southern Kuril Trench

The southern Kuril Trench is one of the most seismically active regions in the world. In this study, marine surveys and observations were performed to construct fault models for possible outer-rise earthquakes. Seismic and seafloor bathymetric surveys indicated that the dip angle of the outer-rise fault was approximately 50°–80°, with a strike that was slightly oblique to the axis of the Kuril Trench. The maximum fault length was estimated to be ~ 260 km. Based on these findings, we proposed 17 fault models, with moment magnitudes ranging from 7.2 to 8.4. To numerically simulate tsunami, we solved two-dimensional dispersive wave and three-dimensional Euler equations using the outer-rise fault models. The results of both simulations yielded identical predictions for tsunami with short-wavelength components, resulting in significant dispersive deformations in the open ocean. We also found that tsunami generated by outer-rise earthquakes were affected by refraction and diffraction because of the source location beyond the trench axis. These findings can improve future predictions of tsunami hazards.Graphical

High-precision 1′ × 1′ bathymetric model of Philippine Sea inversed from marine gravity anomalies

Abstract. The Philippine Sea, located at the edge of the northwestern Pacific Ocean, possesses complex seabed topography. Developing a high-precision bathymetric model for this region is of paramount importance, as it provides fundamental geoinformation essential for Earth observation and marine scientific research, including plate motion, ocean circulation, and hydrological characteristics. The gravity–geologic method (GGM), based on marine gravity anomalies, serves as an effective bathymetric prediction technique. To further strengthen the prediction accuracy of conventional GGM, we introduce the improved GGM (IGGM). The IGGM considers the effects of regional seafloor topography by employing weighted averaging to more accurately estimate the short-wavelength gravity component, along with refining the subsequent modeling of long-wavelength gravity component. In this paper, we focus on seafloor topography modeling in the Philippine Sea based on the IGGM, combining shipborne bathymetric data with the Scripps Institution of Oceanography (SIO) V32.1 gravity anomaly. To reduce computational complexity, the optimal parameter values required for IGGM are first calculated before the overall regional calculation, and then, based on the terrain characteristics and distribution of sounding data, we selected four representative local sea areas as the research objects to construct the corresponding bathymetric models using GGM and IGGM. The analysis indicates that the precision of the IGGM models in four regions is improved to varying degrees, and the optimal calculation radius is 2′. Based on the above finding, a high-precision 1′×1′ bathymetric model of the Philippine Sea (5–35° N, 120–150° E), known as the BAT_PS model, is constructed using IGGM. Results demonstrate that the BAT_PS model exhibits a higher overall precision compared to the General Bathymetric Chart of the Oceans (GEBCO), topo_25.1, and DTU18 models at single-beam shipborne bathymetric points.

Effective Detection of Cu(II) Ions Based on Carbon Dots@Exfoliated Layered Double Hydroxides Composites Fluorescence Probe.

A series of carbon dots@exfoliated layered double hydroxides (CDs@LDH) composites were hydrothermally fabricated by Mg/Al LDH and formamide. The results of FTIR, UV-vis, and XPS spectra in company with HRTEM images showed that crystalline nano CDs formed on the single layer of LDH by Mg-C bond. With the increase of solvothermal reaction time from 2 to 6h, the band gap and the binding energy of aminic and graphitic N species of CDs@LDH composites decreased, whereas the crystallinity increased. The fluorescence peaks of CDs@LDH composites could be deconvoluted into short-wavelength (416nm) and large-wavelength (443nm) components by Gaussian function, and the fluorescence intensities of both components enhanced with the extension of the solvothermal reaction time. The simultaneous enhancements of fluorescence lifetime and quantum yield resulted from the relatively high electron density in graphitic nitrogen of CDs@LDH, whereas the reduction of nonradiative rate was due to the high crystallinity in the carbon core of CDs@LDH. A strong exciton-lattice interaction also has been validated based on the excitation and emission spectra of CDs@LDH, so the fluorescence emission of CDs@LDH composite was heavily related to its crystalline carbon core and nitrogen-containing groups. CDs@LDH with high nitrogen-containing exhibited a superior detection property for Cu2+ ion sensing with the linear range of 26.90 ~ 192.20μM and a limit of detection of 0.1957μM. The photo-induced electron transfer (PET) process dominated the fluorescence quenching of CDs@LDH by Cu2+ ion since the fluorescence lifetime decreased with the increase of Cu2+ ion concentration.

The Influence of Light Wavelength on Human HPA Axis Rhythms: A Systematic Review.

Environmental light entrains many physiological and behavioural processes to the 24 h solar cycle. Such light-driven circadian rhythms are centrally controlled by the suprachiasmatic nucleus (SCN), which receives information from the short-wavelength-sensitive intrinsically photosensitive retinal ganglion cells. The SCN synchronizes local clocks throughout the body affecting sleep/wake routines and the secretion of neuroendocrine-linked hormones such as melatonin from the pineal gland and cortisol via the hypothalamic pituitary adrenal (HPA) axis. Although the effects of light parameters on melatonin have been recently reviewed, whether the experimental variation of the spectral power distribution and intensity of light can induce changes in cortisol rhythms remains unclear. Thus, this systematic review evaluated the effects of daytime exposure to lights of different spectral wavelength characteristics and luminance intensity on the cortisol levels in healthy individuals. A search of the PubMed, Web of Science, EMBASE, CINAHL, Medline, PsycINFO and Cochrane Library databases on 19 June 2023 identified 3418 articles, of which 12 studies (profiling 337 participants) met the inclusion and risk of bias criteria. An analysis of the literature indicated that exposure to bright lights of any colour during the late night or early morning can induce significant increases in cortisol secretion relative to time-matched dim light comparison conditions. Furthermore, exposure to bright lights with stronger short-wavelength (blue/green) components in the early morning typically induced greater increases in cortisol relative to lights with stronger long-wavelength (red) components. Thus, the circadian regulation of cortisol is sensitive to the wavelength composition of environmental lighting, in line with the more commonly studied melatonin. As such, wavelength characteristics should be optimized and reported in light intervention studies (particularly for the investigation of cortisol-associated disorders and HPA axis function), and exposure to short-wavelength light during sensitive periods should be carefully considered in constructed environments (e.g., bedroom and classroom lighting and device screens).

Short-wavelength artificial light affects visual neural pathway development in mice

Nearly all modern life depends on artificial light; however, it does cause health problems. With certain restrictions of artificial light emitting technology, the influence of the light spectrum is inevitable. The most remarkable problem is its overload in the short wavelength component. Short wavelength artificial light has a wide range of influences from ocular development to mental problems. The visual neuronal pathway, as the primary light-sensing structure, may contain the fundamental mechanism of all light-induced abnormalities. However, how the artificial light spectrum shapes the visual neuronal pathway during development in mammals is poorly understood. We placed C57BL/6 mice in three different spectrum environments (full-spectrum white light: 400–750 nm; violet light: 400 ± 20 nm; green light: 510 ± 20 nm) beginning at eye opening, with a fixed light time of 7:00–19:00. During development, we assessed the ocular axial dimension, visual function and retinal neurons. After two weeks under short wavelength conditions, the ocular axial length (AL), anterior chamber depth (ACD) and length of lens thickness, real vitreous chamber depth and retinal thickness (LLVR) were shorter, visual acuity (VA) decreased, and retinal electrical activity was impaired. The density of S-cones in the dorsal and ventral retinas both decreased after one week under short wavelength conditions. In the ventral retina, it increased after three weeks. Retinal ganglion cell (RGC) density and axon thickness were not influenced; however, the axonal terminals in the lateral geniculate nucleus (LGN) were less clustered and sparse. Amacrine cells (ACs) were significantly more activated. Green light has few effects. The KEGG and GO enrichment analyses showed that many genes related to neural circuitry, synaptic formation and neurotransmitter function were differentially expressed in the short wavelength light group. In conclusion, exposure to short wavelength artificial light in the early stage of vision-dependent development in mice delayed the development of the visual pathway. The axon terminus structure and neurotransmitter function may be the major suffering.

Internal structure and kinematics of the Zvenyhorod-Brats’k fault zone of the Ukrainian shield according to geophysical data

Complex geomagnetic and tectonophysical studies were performed in order to characterize in detail the heterogeneity of the Earth’s crust of the Zvenyhorod-Bratskfault zone and to clarify its internal structure and kinematics. Based on the results of magnetometric studies, maps of the different wavelength components of magnetic anomalies were obtained, the sources of which are associated with different layers of the crust; the magnetization of the upper, middle and lower parts of the crust was estimated; 2D and 3D magnetic models of individual structures and areas were developed; geological and tectonic interpretations were performed.
 The Zvenyhorod-Bratskfault zone is clearly manifested in the regional component of the geomagnetic field, separating its maxima and minima zones, and is also reflected by linear anomalies and bands of the short-wavelength component of the upper part of the crustal section. At the same time, it separates areas of the Earth’s crust with fundamentally different types of sources and their magnetization values: in the west, linear sources of the upper and middle crust of the GSZ are characterized by significant magnetization (up to 3—6 A/m) in contrast to the oval-shaped sources of the Ingul block with magnetization up to 1 A/m m.
 Tectonophysical measurements of structural and textural elements of rocks were carried out at four sites along the rivers Velyka Vys’, Kilten’, Suhyi Tashlyk and Mertvovid. Processing and interpretation of field measurements of structural textural elements of rocks were done by the structural-paragenetic method of tectonophysics for III-IV depth levels using the Stereonet program.
 It was established that the Zvenyhorod-Bratskfault zone was formed ≤2.45 billion years ago and consists of rectilinear shear zones related to different stages of fault formation. However, the main factor in the formation of the fault zone is the Pervomaisk stage, during which the L-shears with a strike azimuth of 345° and R-shears with a strike azimuth of 357° were formed. The presence of Archean phases of shear in it can testify to the earlier formation of the Zvenyhorod-Bratskfault zone relative to the Pervomaysk one.
 The Proterozoic cycle of activation (~2.1—1.70 billion years ago) contributed to the formation of deposits and ore manifestations of minerals within the Zvenyhorod-Bratskfaults zone.

Finite-frequency sensitivity kernels and hierarchical traveltime and waveform inversion of direct and reflected waves from vertical seismic profile data

Wave-equation-based traveltime or waveform inversion updates the velocity model along finite-frequency sensitivity kernels and exhibits higher accuracy than ray-based tomography. Owing to special geometry, the kernels for vertical seismic profile (VSP) data are different from those for surface seismic data. We have used the Born approximation to compute the traveltime and waveform kernels for direct and reflected waves from VSP data. Based on the property of sensitivity kernels for different information and arrivals, we develop a hierarchical inversion scheme: joint wave-equation traveltime inversion (JWETI) of direct and reflected waves, joint waveform inversion (JWI) of direct and reflected waves, and full-waveform inversion (FWI) of the reflected wave. The traveltime kernels, the waveform kernels, and the migration isochrones are used to retrieve the long-, intermediate-, and short-wavelength components of the velocity model, respectively. Numerical tests on synthetic and real walkway VSP data reveal that the JWETI stage obtains a plausible velocity macromodel, which can be treated as a starting model for subsequent JWI and FWI stages. The JWI stage is a transition between JWETI and FWI and helps to improve the structures of the deep layers of the model. The FWI stage offers some high-wavenumber contents to the inverted model. For the VSP survey, the transmitted direct waves can be used to reduce the dependence of FWI on the initial model. However, the conventional reflection-based wave-equation traveltime inversion and FWI still suffer from cycle skipping when the initial model is far away from the real model. In contrast, the hierarchical inversion scheme can yield reasonable inversion results around the borehole, even when large velocity errors are present in the starting model.

Review on the study of potential health hazards caused by blue light due to Melanopsin activity

Humans live in a 24-hour environment, in which light and darkness follow a diurnal pattern. In humans, the known effects of light on circadian rhythms and sleep are all, without exception, mediated by the retina. The retina is a fine layer of nerve tissue at the back of our eyes, containing specialized photoreceptors. Melanopsin RGCs are extremely sensitive to blue light and even exposure to light levels as low as the one from a smart-phone or light emitting e-readers are associated with disruptions of circadian rhythm. Melanopsin absorbs light in the short-wavelength range of the visible spectrum, with λmax at or near 480 nm. High-intensity blue light from any source is potentially hazardous to the eye. Industry sources of blue light are purposely filtered or shielded to protect users. However, it may be harmful to look directly at many high-power consumer LEDs simply because they are very bright. When Melanopsin is activated by the short wavelength component of light, it suppresses Melatonin synthesis. This action is controlled mainly by light could affect several functions including the regulation of intraocular pressure. Blue light or blue-violet light can be damaging to delicate retinal cells deep in the eye. No one knows exactly what causes dry macular degeneration. Research indicates that it may be a combination of family genes and environmental factors, including smoking, obesity and diet. The condition develops as the eye ages. Additionally, our studies have shown blue light is a risk factor for the onset of age-related macular degeneration, which is a progressive condition that can lead to vision loss over.

Enhanced Short-Wavelength Marine Gravity Anomaly Using Depth Data

Satellite altimetry cannot accurately derive the short-wavelength component of ocean gravity anomaly. Since the short-wavelength seabed topography affects the gravity anomaly, we can forward the short-wavelength gravity anomaly by using seabed topography to make up for the shortcomings of altimetry. Based on the Global Marine Gravity Anomaly version 1 (GMGA1) previously released by our group, and on Parker’s formula, the short-wavelength gravity anomaly is forwarded by using the seabed topographic model SRTM15+V2.4, and a new product, Global Marine Gravity Anomaly Version 2 (GMGA2), is obtained. Compared with internationally recognized gravity field products such as SIO V32.1 and DTU17, the accuracy of GMGA2 is 2.5mGal, which is 0.7 mGal higher than GMGA1, and the absolute differences smaller than 5mGal account for more than 96%. An evaluation using ship-borne gravity data showed the accuracy of GMGA2 is 4.8 mGal, which is 0.3 mGal higher than GMGA1. It is concluded from the above results that using the forward method with water depth data significantly improves the short-wavelength gravity anomaly of the altimetry-derived gravity field model, and the accuracy of GMGA2 is close to that of the advanced international level.

Sensing the Terrestrial and Atmospheric Hydrological Dynamic using Satellite Gravimeter and GNSS

Geodetic observation methods, e.g., satellite gravimeter and Global Navigation Satellite System (GNSS), are mainly used for determining the Earth’s gravity field and reference system. However, many efforts have been made to adopt the mentioned methods for estimating hydrological dynamics. The satellite gravimeter of the Gravity Recovery and Climate Experiment and its Following-On missions (GRACE/GRACE-FO) have proven to capture the terrestrial hydrological variation. Also, thanks to its signal propagation through the atmosphere medium, GNSS can be used for sensing the hydrology variation in the atmosphere, i.e., troposphere medium. This study aims to explore GRACE/GRACE-FO and GNSS observations to estimate the respective terrestrial and atmospheric hydrological variation in Bandung, Indonesia. Monthly solutions of GRACE/GRACE-FO provided by three agencies were used to estimate the terrestrial hydrological variation. We also used the continuous GNSS site of ITB1 and calculated the atmospheric hydrological series in the form of precipitable water vapor. We found that the terrestrial hydrological series varies approximately ±20 cm, while the precipitable water vapor ranges between 1 to 5 centimeters. Further, we observed long-wavelength components from terrestrial and atmospheric hydrological variations that correspond to dry and wet seasons. However, we only sensed shorter wavelength components of hydrological dynamic from GNSS observation and not for the GRACE as the estimated hydrological variations were estimated monthly. At the same time, delays were calculated every two hours using GNSS observations. Nevertheless, this study shows the potential uses of geodetic approaches such as satellite gravity and GNSS observations to capture the hydrological dynamic.

Rolling resistance model for estimation of friction fluctuation in linear ball guideways

Linear ball guideways are widely employed in machine tool drive systems. Friction fluctuation of linear ball guideways causes fluctuations in the feed rate that results in contour errors in synchronous motions while using several feed drives. In this study, a practical model of rolling resistance is proposed for a model-based design of the raceway profile that realizes a smooth feed motion. In the proposed model, the rolling resistance is obtained from the preload and two contact angles at the upper and lower raceways. The preload variation is represented by a simplified spring model. The validity of the proposed model is experimentally verified. The variation in the rolling resistance is influenced by the phase difference between the upper and lower raceway profiles. The resistance variation can be decreased by setting the phase difference to the half period of the profile component. The experimental results indicate that the fluctuation components of the rolling resistance, with a wavelength longer than the contact diameter between the ball and raceway, can be correctly estimated. The estimation error for the shorter-wavelength component is not a crucial issue because the rolling resistance fluctuation is small for such a component. The verification results show that the proposed model can provide an effective guideline for the raceway profile design to reduce the rolling resistance fluctuation to an acceptable level.

Engineering the high-frequency components of coherent supercontinuum generation in hybrid optical fibers with yttrium aluminum garnet core

Coherent supercontinuum (SC) generation in optical fibers has spurred extensive research interest and found many applications. Here, we report a hybrid optical crystal fiber with an yttrium aluminum garnet (YAG) core. The optimized fiber features broad and flat near-zero normal dispersion and three wavelengths where the dispersion slope is zero. Through numerical modeling, we in detail investigate the influence of the pump wavelengths near the three wavelengths on the spectral broadening. The spectral broadening shows asymmetric towards the high-frequency region. The longer the pump wavelength, the more is the short wavelength components of the generated SC. Thus, the high-frequency components of the SC spectra can be engineered in the fiber. Interestingly, the occurrence of optical wave breaking (OWB) in the low-frequency region is prior to that in the high-frequency region when the pump wavelength is at 1660 nm. The broadest spectrum could be obtained when the pump wavelength is near the middle wavelength where the dispersion slope is zero. The result provides a new strategy for fiber design and broadband SC generation, which is different from the viewpoint that the broadest spectrum can be obtained when the pump wavelength near the local maximum dispersion. Combined with high nonlinearity and flat dispersion, the hybrid fiber allows octave-spanning SC generation with the pump power low to 1 kW at 1100 nm. This provides the potentials for high-power, broadband, and coherent SC generation at 1064 nm where the dispersion slope is near zero.

Depolarization of the supercontinuum induced by linearly and circularly polarized femtosecond laser pulses in water

The supercontinuum (SC) is generally assumed to inherit the polarization of the incident pulse in isotropic media. In this study, we experimentally investigated the polarization properties of SC spectra induced by different polarized femtosecond lasers in water. The results show that the extent of depolarization of the SC induced by a quasicircularly polarized pulse is more pronounced than that of a quasilinearly polarized pulse. In terms of the different spectral components, the long-wavelength components experienced more depolarization, and the short-wavelength components tended to be linearly polarized for both polarized input femtosecond lasers. The depolarization mechanism can be attributed to two factors, namely, the energy coupling between the two polarized components of the input femtosecond pulse, and the various degrees of nonlinear birefringence experienced by different spectral components of the SC during propagation.

A Smoothing Scheme for Seismic Wave Propagation Simulation with a Mixed FEM of Diffusionized Wave Equation

In this paper, we propose a smoothing scheme for seismic wave propagation simulation. The proposed scheme is based on a diffusionized wave equation with the fourth-order spatial derivative term. So, the solution requires higher regularity in the usual weak formulation. Reducing the diffusionized wave equation to a coupled system of diffusion equations yields a mixed FEM to ease the regularity. We mathematically explain how our scheme works for smoothing. We construct a semi-implicit time integration scheme and apply it to the wave equation. This numerical experiment reveals that our scheme is effective for filtering short wavelength components in seismic wave propagation simulation.

Observation of square- and h-shaped pulse from a mode-locked erbium-doped fiber laser.

We demonstrate the generation of a type of square-shaped pulse in a passively mode-locked erbium-doped fiber laser based on the nonlinear optical loop mirror technique. Through adjusting the pump power and polarization state, square-shaped pulses are generated. Furthermore, we investigate the pulse profile in relation to the optical spectrum. By filtering out short-wavelength spectrum components gradually, pulse shaping is achieved, and the top of the square-shaped pulse becomes flat. Subsequently, by filtering out long-wavelength spectrum components, a type of h-shaped pulse is obtained and the formation reason is also investigated.

Long and Short Wavelength of Geodetic Strain Rate Tapering Earthquake Potential in Western Java

Shallow earthquake produced by intra-island fault in a populated region could be a catastrophic disaster. Java island is the most populated area specifically in Western Java since there include Jakarta, the capital city of Indonesia. Cimandiri, Lembang and Baribis fault as main intra-island fault are considered to be responsible due to some shallow historical earthquake in Western Java. However, convergent plate margin such as Java Island generates a broad spectrum of deformation pattern that potentially distracts the deformation due to Baribis fault. In addition, slow relative motion of Sunda block and postseismic deformation due to the 2006 Java tsunami earthquake involve along those fault. Here, we intend to conduct a wavelength decomposition of strain rate calculated from GNSS (Global Navigation Satellite System) data. We expect to separate long wavelength due to wider-region deformation such as deformation due to the interacting plate and postseismic deformation to obtain Short wavelength due to each fault. We utilized the daily position of recent continuous geodetic data to produce strain rate. Therefore, we could apply a moving average filter to extract a short wavelength component. We obtained long wavelength (-150 to 150 nanostrain/yr) in Western Java shows extension indicating the postseismic effect is still continuous while short wavelength (-75 to 75 nanostrain/yr) varies in space.

Interrelation between Colorimetric and Spectral Parameters of White Led Lamps

The interrelation between colorimetric (correlated color temperature) and spectral (intensity ratio of spectral emission bands) parameters of white LED lamps for general lighting has been established based on an analysis of test results for a set of lamps during aging. Deconvolution of the lamp radiation spectra is used to show that the change in color temperature is mainly due to a change in the intensity ratio of the 450-nm band originating from the diode heterostructure and the long-wavelength component of the nonelementary yellow band of the phosphor radiation with a maximum at 580 nm. However, the shorter-wavelength component with a maximum of 530 nm manifests itself mainly in the change of the total luminous flux. A possible cause of the change in the intensity of the spectral components of the nonelementary phosphor radiation band may be both thermal effects and structural changes in the phosphor material.

Спектры электролюминесценции и структура анодного оксида алюминия при его формировании в химически чистой воде и спиртах

For a film of aluminum oxide (Al2O3) formed in distilled water (H2O), a linear growth was revealed during the high-voltage anodization time of 2000 s, and it was found that its electroluminescence (EL) is reliably recorded at an Al2O3 thickness of about 120 nm. It is shown that in DV and its deuterium-containing analogue, deuterium water (D2O), the electrolysis formation of Al2O3 is possible. cellular-nanoporous structure, identical to that formed in aqueous solutions of electrolytes. It was found that the presence of such a structure in the oxide is not a prerequisite for the generation of its EL. The EL spectrum of Al2O3 in H2O and D2O, as well as in “water-like” electrolytes: ethylene glycol, N, N-dimethylethanolamine, and isopentanol, was recorded for the first time. In the investigated range of 400–700 nm, significant differences in the luminescence in water and the above alcohols are revealed. For EL, the short-wavelength component with a wavelength of the order of 440 nm dominates in water, and in alcohols, the long-wavelength component with a maximum at 625 nm. In this case, nonstationarity of luminescence is observed both in the spectral composition and in the intensity of individual parts of the spectrum for the entire time of aluminum anodization.

Quantitative Color Fundus Autofluorescence in Patients with Diabetes Mellitus.

A new short wavelength confocal blue-light 450 nm-fundus autofluorescence (color-FAF) allows for visualization of minor fluorophores (e.g., advanced glycation end products, AGEs), besides lipofuscin. The aim of the present pilot study was to quantitatively evaluate color-FAF in patients with diabetes mellitus (DM) and to correlate these data with different stages of retinal disease severity. Optical coherence tomography and color-FAF images of 193 patients/eyes and 18 controls were analyzed using a custom software for quantification of the long (red) and short (green) wavelength components of the emission spectrum (REFC/GEFC). Measurements were performed in nine quadrants of the 6-mm ETDRS macular grid. Foveal GEFC and REFC intensities were higher in patients with DM compared to controls (p = 0.015 and p = 0.006 respectively) and in eyes with center involving diabetic macular edema (DME) compared to eyes without DME (p < 0.001). A positive correlation was found between GEFC and REFC intensities and central retinal thickness, r = 0.37 (p < 0.001) and r = 0.42 (p < 0.001), respectively. No differences were found in color-FAF among different DR severity groups. Quantitative color-FAF could become helpful for the metabolic evaluation of retina in patients with DM and in DME; however, further histologic and immunohistochemical studies on distribution of different retinal fluorophores in DM are needed to better understand its role.

Estimation of Curie point depth and geothermal gradient in parts of the Bida Basin, Nigeria

The purpose of this work is to estimate the Curie point depth, heat flow and geothermal gradient from spectral analysis of aeromagnetic data over the Bida and Baro areas, Bida Basin, north central Nigeria. The area covered is approximately 6050 km2 and bounded by latitudes 8° 30′ and 9° 30′ north and longitudes 6° 0′ and 6° 30′ east. The aeromagnetic maps were digitised at an equal interval, and the regional values were removed using polynomial fitting. The resulting residual data were subjected to the upward continuation technique to suppress the short-wavelength components of the residual magnetic anomalies. The upward continuation residual map was divided into eight overlapping blocks, and each block was spectrally analysed. The estimated Curie point depth ranges from 13.6 to 27.2 km, the geothermal gradient ranges from 21.3 to 42.6°C/km with an average value of 34.4°C/km and the corresponding heat flow ranges from 53.2 to 106.6 mW/m2. The average value of the geothermal gradient of 34.4°C/km indicates the possibility of hydrocarbon maturation in the area. Areas of geothermal anomalies with gradients greater than 40°C/km may be prospective for geothermal energy usage in Nigeria for generation of electricity.