High-Resolution Cooperate Density-Integrated Inversion Method of Airborne Gravity and Its Gradient Data

Airborne (or satellite) gravity measurement is a commonly used remote sensing method to obtain the underground density distribution. Airborne gravity gradiometry data have a higher horizontal resolution to shallower causative sources than airborne gravity anomaly, so joint exploration of airborne gravity and its gradient data can simultaneously obtain the anomaly feature of sources with different depths. The most commonly used joint inversion method of gravity and its gradient data is the data combined method, which is to combine all the components into a data matrix as mutual constraints to reduce ambiguity and non-uniqueness. In order to obtain higher resolution results, we proposed a cooperate density-integrated inversion method of airborne gravity and its gradient data, which firstly carried out the joint inversion using cross-gradient constraints to obtain two density structures, and then fused two recovered models into a result through Fourier transform; finally, data combined joint inversion of airborne gravity, and gradient data were reperformed to achieve high-resolution density result using fused density results as a reference model. Compared to the data combined joint inversion method, the proposed cooperate density-integrated inversion method can obtain higher resolution and more accurate density distribution of shallow and deep bodies meanwhile. We also applied it to real data in the mining area of western Liaoning Province, China. The results showed that the depth of the skarn-type iron mine in the region is about 900–1300 m and gives a more specific distribution compared to the geological results, which provided reliable data for the next exploration plan.

Bouguer Anomaly of Geothermal Reservoir at Tiris Area, Probolinggo, East Java, Indonesia

Research related to the geothermal system in the Tiris geothermal area (TGA) Probolinggo Regency has been conducted using the gravity method. This study aims to investigate the subsurface structure, with a target on estimating geothermal reservoir rocks from the study area. This study utilized the Gravity meter La Coste & Romberg type G-1503 on 116 acquisition points in an area of 2.16 km2, covering all geothermal manifestation points in TGA. The gravity measurement data obtained is then processed through gravity corrections, which include: conversion into milli-Gals (mGal) units, tidal correction, drift correction, latitude correction, free air correction, Bouguer correction, and terrain correction. These corrections to obtain a complete Bouguer anomaly (CBA) value. The study area shows the CBA value on a horizontal plane which ranges from 0.1 mGal to 4.2 mGal. The separation of the regional and residual Bouguer anomaly from the CBA on a horizontal plane employed the Moving Average method through spectrum analysis. The value of residual Bouguer anomaly ranges from -0.7 mGal to 2.7 mGal. The low anomalies are scattered in the northwest, and a small number are spread in the northeast and southeast, while the high anomalies are in the middle of the study area. The result of 3D inversion modeling finds that the study area's subsurface structure consists of four rock layers, namely lapilli tuff, tuffaceous breccia, volcanic breccia, and basalt. Volcanic breccia is approximated as geothermal reservoir rocks at a depth of 700 to 1000 meters below the acquisition point. In contrast, basalt is supposed to be intrusive igneous rock because it tends to break through the surface at a depth of 348 to 350 meters below the acquisition point. The presence of these intrusive rocks can be predicted through spectrum analysis result, which shows a regional anomaly source at a depth of 348 meters below the acquisition point. This intrusion rock is suspected to be a heat source rock in the geothermal system in the study area.

Experimental study on improving the accuracy of marine gravimetry by combining moving-base gravimeters with GNSS antenna array

The gravity field is one of the Earth’s basic physical fields. The geoid can be calculated and the tectonic activity underground can be inversed by gravity anomaly. With the development of various ship-borne gravimeters and navigation technology, including the Global Navigation Satellite System (GNSS) and Strapdown Inertial Navigation System (SINS), the precision of marine gravimetry has been significantly improved (achieve or better than 1mGal). Errors arising from calculations of the correction term have become the main source of gravity measurement errors. At present, the traditional approach is to deploy a GNSS antenna, connect the GNSS antenna to the gravimeter, record the real-time position through data acquisition software, and then use this position to calculate the gravity correction item afterward. Two errors are inevitable. (1) The GNSS antenna position error is large. The pseudorange point positioning method is generally used to obtain real-time GNSS antenna positions, and the positioning accuracy is poor compared with that of precise point positioning. (2) The position coordinates of the gravimeter contain systematic errors related to the ship’s attitude. In this paper, a joint experiment including GNSS antenna arrays and ship-borne gravimeters was designed to evaluate the measurement accuracy via repeat lines on the same ship. The experimental results show the following: (1) attitude accuracies of 0.0299° for the yaw angle, 0.0361° for the pitch angle, and 0.1671° for the roll angle can be obtained at baseline lengths of 25 and 4 m. (2) The GNSS antenna array has an obvious role in determining the point acceleration in the low-frequency band (0–0.01 Hz) and the point position and velocity in the high-frequency band (0.01–1 Hz). (3) The vertical position eccentricity causes an absolute error of 1 mGal and a relative error of $${10}^{-1}$$ 10 - 1 mGal in gravity measurements and can be corrected by the GNSS antenna array method. (4) Using a GNSS antenna array can obviously improve the measurement accuracy of an instrument with a precision equaling or exceeding 1 mGal, but cannot obviously improve that to an instrument with poor precision (2 mGal or below).

Thermodynamics of Ideal Gas at Planck Scale with Strong Quantum Gravity Measurement

More recently in J. Phys. A: Math. Theor. 53, 115303 (2020), we have introduced a set of noncommutative algebra that describes the space-time at the Planck scale. The interesting significant result we found is that the generalized uncertainty principle induced a maximal length of quantum gravity which has different physical implications to the one of generalized uncertainty principle with minimal length. The emergence of a maximal length in this theory revealed strong quantum gravitational effects at this scale and predicted the detection of gravity particles with low energies. To make evidence of these predictions, we study the dynamics of a free particle confined in an infinite square well potential in one dimension of this space. Since the effects of quantum gravity are strong in this space, we show that the energy spectrum of this system is weakly proportional to the ordinary one of quantum mechanics free of the theory of gravity. The states of this particle exhibit proprieties similar to the standard coherent states which are consequences of quantum fluctuation at this scale. Then, with the spectrum of this system at hand, we analyze the thermodynamic quantities within the canonical and micro-canonical ensembles of an ideal gas made up of N indistinguishable particles at the Planck scale. The results show a complete consistency between both statistical descriptions. Furthermore, a comparison with the results obtained in the context of minimal length scenarios and black hole theories indicates that the maximal length in this theory induces logarithmic corrections of deformed parameters which are consequences of a strong quantum gravitational effect.