History Of Geophysics Research Articles

President's Page: The geophysical landscape in the Middle East

The Middle East has experienced dramatic changes since the discovery of oil in Persia (now Iran) in 1908 and then in Saudi Arabia in 1938. Preceding these discoveries, geophysics as we now know it was not applied or even well known in the region. On the other hand, geology was well established in the Middle East by geologists from the region and abroad. One of the first geologic departments in the Middle East was the geology department at Cairo University, Egypt, which started with the university's establishment in 1925. The geophysics department, conversely, was not established until 1982. Historically, some may argue that the history of geophysics in the Middle East can be traced back to about 600 BC, although the first scientific book relating to geophysics (Fuyuzat-i Miknatissiye, which discussed earth's magnetism) was not translated and printed until 1731.

The first measurements of gravity in Australia

In his comprehensive history of geophysics in Australia Dr A A Day (Day, 1966) first refers to gravity measurements being made in Sydney by L. S. de Freycinet and his company in 1819. They used pen...

An optimal tropospheric tomography approach with the support of an auxiliary area

Abstract. Among most current tropospheric tomography studies, only the signals crossing out from the top boundary of the tomographic area are used for reconstructing the three-dimensional water vapour field, while signals penetrating from the side faces of the tomographic body are ignored as invalid information. Such a method wastes the valuable Global Navigation Satellite System (GNSS) observations and decreases the utilisation efficiency of GNSS rays. This is the focus of this paper, which tries to effectively use signals penetrating from the side faces of the tomographic body for water vapour reconstruction. An optimised tropospheric tomography method is proposed using an auxiliary area. The top height of the tomography body is determined based on the average water vapour distribution derived from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) products. In addition, the coefficients of a negative exponential function between the adjacent layers for vertical constraints are fitted using the COSMIC RO profiles. Thirteen GPS stations are selected in the CORS Network of Texas to perform the tomographic experiment and validate the performance of the proposed method at 00:00 and 12:00 UTC daily using the radiosonde data for a period of 15 days. Compared to the conventional method, the accuracy of the reconstructed water vapour information derived from the proposed method is increased by 14.37 % and 16.13 %, respectively, in terms of mean root mean square (rms) and mean absolute error (MAE). The tomographic results obtained from the proposed method are further validated with the slant water vapour (SWV) data derived using the GAMIT (GNSS processing software package). Results show that the rms and MAE accuracy of SWV values has been improved by 18.18 % and 27.62 %, respectively, when compared to the conventional method. Keywords. History of geophysics (atmospheric sciences)

Seasonal characteristics of small- and medium-scale gravity waves in the mesosphere and lower thermosphere over the Brazilian equatorial region

Abstract. The present work reports seasonal characteristics of small- and medium-scale gravity waves in the mesosphere and lower thermosphere (MLT) region. All-sky images of the hydroxyl (NIR-OH) airglow emission layer over São João do Cariri (7.4∘ S, 36.5∘ W; hereafter Cariri) were obtained from September 2000 to December 2010, during a total of 1496 nights. For investigation of the characteristics of small-scale gravity waves (SSGWs) and medium-scale gravity waves (MSGWs), we employed the Fourier two-dimensional (2-D) spectrum and keogram fast Fourier transform (FFT) techniques, respectively. From the 11 years of data, we could observe 2343 SSGW and 537 MSGW events. The horizontal wavelengths of the SSGWs were concentrated between 10 and 35 km, while those of the MSGWs ranged from 50 to 200 km. The observed periods for SSGWs were concentrated around 5 to 20 min, whereas the MSGWs ranged from 20 to 60 min. The observed horizontal phase speeds of SSGWs were distributed around 10 to 60 m s−1, and the corresponding MSGWs were around 20 to 120 m s−1. In summer, autumn, and winter both SSGWs and MSGWs propagated preferentially northeastward and southeastward, while in spring the waves propagated in all directions. The critical level theory of atmospheric gravity waves (AGWs) was applied to study the effects of wind filtering on SSGW and MSGW propagation directions. The SSGWs were more susceptible to wind filtering effects than MSGWs. The average of daily mean outgoing longwave radiation (OLR) was also used to investigate the possible wave source region in the troposphere. The results showed that in summer and autumn, deep convective regions were the possible source mechanism of the AGWs. However, in spring and winter the deep convective regions did not play an important role in the waves observed at Cariri, because they were too far away from the observatory. Therefore, we concluded that the horizontal propagation directions of SSGWs and MSGWs show clear seasonal variations based on the influence of the wind filtering process and wave source location. Keywords. Atmospheric composition and structure (airglow and aurora) – electromagnetics (wave propagation) – history of geophysics (atmospheric sciences)

A case study of mesospheric planetary waves observed over a three-radar network using empirical mode decomposition

Abstract. In this paper an attempt is made to study equatorial Kelvin waves using a network of three radars: Kototabang (0.204∘ S, 100.320∘ E) meteor radar, Pameungpeuk (7.646∘ S, 107.688∘ E) medium-frequency radar, and Pontianak (0.003∘ S, 109.367∘ E) medium-frequency radar. We have used the continuous data gathered from the three radars during April–May 2010. Empirical mode decomposition (EMD), Lomb–Scargle periodogram (LSP) analysis, and wavelet techniques are used to study the temporal and altitude structures of planetary waves. Here, we used a novel technique called EMD to extract the planetary waves from wind data. The planetary waves of ∼ 6.5 and ∼ 3.6 days periodicity are observed in all three radar stations with peak amplitudes of about 12 and 11 m s−1, respectively. The 3.6-day wave has an average vertical wavelength from the three radars of about 42 km. The 3.6- and 6.5-day planetary waves are particularly strong in the zonal wind component. We find that the two waves are present at the 84–94 km height region. The observed features of the 3.6- and 6.5-day waves at the three tropical-latitude stations show some correspondence with the results reported for the equatorial-latitude stations. Keywords. Electromagnetics (wave propagation) – history of geophysics (atmospheric sciences) – meteorology and atmospheric dynamics (middle atmosphere dynamics)

Araucaria growth response to solar and climate variability in South Brazil

Abstract. In this work, the Sun–Earth–climate relationship is studied using tree growth rings of Araucaria angustifolia (Bertol.) O. Kuntze collected in the city of Passo Fundo, located in the state of Rio Grande do Sul (RS), Brazil. These samples were previously studied by Rigozo et al. (2008); however, their main interest was to search for the solar periodicities in the tree-ring width mean time series without interpreting the rest of the periodicities found. The question arises as to what are the drivers related to those periodicities. For this reason, the classical method of spectral analysis by iterative regression and wavelet methods are applied to find periodicities and trends present in each tree-ring growth, in Southern Oscillation Index (SOI), and in annual mean temperature anomaly between the 24 and 44∘ S. In order to address the aforementioned question, this paper discusses the correlation between the growth rate of the tree rings with temperature and SOI. In each tree-ring growth series, periods between 2 and 7 years were found, possibly related to the El Niño/La Niña phenomena, and a ∼ 23-year period was found, which may be related to temperature variation. These novel results might represent the tree-ring growth response to local climate conditions during its lifetime, and to nonlinear coupling between the Sun and the local climate variability responsible to the regional climate variations. Keywords. History of geophysics (solar–planetary relationships) – meteorology and atmospheric dynamics (climatology; palaeoclimatology)

Determination of gravity wave parameters in the airglow combining photometer and imager data

Abstract. Mesospheric airglow measurements of two or three layers were used to characterize both vertical and horizontal parameters of gravity waves. The data set was acquired coincidentally from a multi-channel filter (Multi-3) photometer and an all-sky imager located at São João do Cariri (7.4∘ S, 36.5∘ W) in the equatorial region from 2001 to 2007. Using a least-square fitting and wavelet analysis technique, the phase and amplitude of each observed wave were determined, as well as the amplitude growth. Using the dispersion relation of gravity waves, the vertical and horizontal wavelengths were estimated and compared to the horizontal wavelength obtained from the keogram analysis of the images observed by an all-sky imager. The results show that both horizontal and vertical wavelengths, obtained from the dispersion relation and keogram analysis, agree very well for the waves observed on the nights of 14 October and 18 December 2006. The determined parameters showed that the observed wave on the night of 18 December 2006 had a period of ∼43.8±2.19 min, with the horizontal wavelength of 235.66 ± 11.78 km having a downward phase propagation, whereas that of 14 October 2006 propagated with a period of ∼36.00±1.80 min with a horizontal wavelength of ∼195±9.80 km, and with an upward phase propagation. The observation of a wave taken by a photometer and an all-sky imager allowed us to conclude that the same wave could be observed by both instruments, permitting the investigation of the two-dimensional wave parameter. Keywords. Atmospheric composition and structure (airglow and aurora) – electromagnetics (wave propagation) – history of geophysics (atmospheric sciences)

Depth of origin of ocean-circulation-induced magnetic signals

Abstract. As the world ocean moves through the ambient geomagnetic core field, electric currents are generated in the entire ocean basin. These oceanic electric currents induce weak magnetic signals that are principally observable outside of the ocean and allow inferences about large-scale oceanic transports of water, heat, and salinity. The ocean-induced magnetic field is an integral quantity and, to first order, it is proportional to depth-integrated and conductivity-weighted ocean currents. However, the specific contribution of oceanic transports at different depths to the motional induction process remains unclear and is examined in this study. We show that large-scale motional induction due to the general ocean circulation is dominantly generated by ocean currents in the upper 2000 m of the ocean basin. In particular, our findings allow relating regional patterns of the oceanic magnetic field to corresponding oceanic transports at different depths. Ocean currents below 3000 m, in contrast, only contribute a small fraction to the ocean-induced magnetic signal strength with values up to 0.2 nT at sea surface and less than 0.1 nT at the Swarm satellite altitude. Thereby, potential satellite observations of ocean-circulation-induced magnetic signals are found to be likely insensitive to deep ocean currents. Furthermore, it is shown that annual temporal variations of the ocean-induced magnetic field in the region of the Antarctic Circumpolar Current contain information about sub-surface ocean currents below 1000 m with intra-annual periods. Specifically, ocean currents with sub-monthly periods dominate the annual temporal variability of the ocean-induced magnetic field. Keywords. Electromagnetics (numerical methods) – geomagnetism and paleomagnetism (geomagnetic induction) – history of geophysics (transport)

Simulating the dependence of seismo-ionospheric coupling on the magnetic field inclination

Abstract. Infrasound generated during a seismic event upon reaching the ionospheric heights possesses the ability to perturb the ionosphere. Detailed modelling investigation considering 1-D dissipative linear dynamics, however, indicates that the magnitude of ionospheric perturbation strongly depends on the magnetic field inclination. Physics-based SAMI2 model codes have been utilized to simulate the ionosphere perturbations that are generated due to the action of the vertical wind perturbations associated with the seismic infrasound. The propagation of the seismic energy and the vertical wind perturbations associated with the infrasound in the model has been considered to be symmetric about the epicentre in the north–south directions. Ionospheric response to the infrasound wind, however, has been highly asymmetric in the model simulation in the north–south directions. This strong asymmetry is related to the variation in the inclination of the Earth's magnetic field north and south of the epicentre. Ionospheric monitoring generally provides an efficient tool to infer the crustal propagation of the seismic energy. However, the results presented in this paper indicate that the mapping between the crustal process and the ionospheric response is not a linear one. These results also imply that the lithospheric behaviour during a seismic event over a wide zone in low latitudes can be estimated through ionospheric imaging only after factoring in the magnetic field geometry. Keywords. Atmospheric composition and structure (pressure, density, and temperature) – history of geophysics (atmospheric sciences) – ionosphere (ionosphere–atmosphere interactions)

Omori’s law: a note on the history of geophysics

In the late nineteenth century, the Japanese seismologist Omori discovered the first law of earthquake physics, which states that the rate of aftershocks decreases hyperbolically with time. Over the years since then, there has been a vast amount of literature on this law, and the significance of its discovery has been universally recognized. There is, however, a profound division of opinion as to the interpretation of the law. Some argue that Omori just proposed a simple data-fitting formula and replace this formula by a power-law one with a negative fractional exponent, whereas for others the Omori law makes physical sense. The paper describes the history and essence of Omori’s discovery, with special attention paid to interpretational questions. It is shown that Omori’s original formulation of the law correlates well with the current understanding of the rock destruction mechanism at the earthquake focus.

Закон Омори (из истории геофизики)

Закон Омори (из истории геофизики)

A column on the history and culture of geophysics and science in general

November 2015 marks the 100th anniversary of Einstein's theory of general relativity (GR). He published four papers on the subject in November 1915. Remarkable! The first two papers led to the field equations of GR, and the other two laid out vital consequences of the theory, including the anomalous precession of the perihelion of Mercury (unexplained since 1859) and the gravitational bending of light. The latter phenomenon was confirmed famously by Eddington's 1919 observation of a total solar eclipse and the shift of apparent position for stars, the light of which passed very near the sun. Einstein, already famous, became a household name — an early 20th-century superstar.

Expanding Earth and declining gravity: a chapter in the recent history of geophysics

Abstract. Although speculative ideas of an expanding Earth can be found before World War II, it was only in the 1950s and 1960s that the theory attracted serious attention among a minority of earth scientists. While some of the proponents of the expanding Earth adopted an empiricist attitude by disregarding the physical cause of the assumed expansion, others argued that the cause, either fully or in part, was of cosmological origin. They referred to the possibility that the gravitational constant was slowly decreasing in time, as first suggested by P. Dirac in 1937. As a result of a stronger gravitation in the past, the ancient Earth would have been smaller than today. The gravitational argument for an expanding Earth was proposed by P. Jordan and L. Egyed in the 1950s and during the next 2 decades it was discussed by several physicists, astronomers and earth scientists. Among those who for a period felt attracted by "gravitational expansionism" were A. Holmes, J. Tuzo Wilson and F. Hoyle. The paper examines the idea of a varying gravitational constant and its impact on geophysics in the period from about 1955 to the mid-1970s.

A column on the history and culture of geophysics and science in general

As I continue with duties as SEG President, I also enjoy looking back at adventures in the past, including my presentation of the SEG Distinguished Instructor Short Course in 2012.

A column on the history and culture of geophysics and science in general

As I continue to explore exciting opportunities in 2015, I also enjoy looking back at past adventures, including my presentation of the SEG Distinguished Instructor Short Course in 2012.

Seismos: A column on the history and culture of geophysics and science in general

This year, I serve as President of SEG, and I am beginning to see that things are going to be busy, but the “Seismos” column in The Leading Edge is mentioned by a surprising number of geophysicists I meet around the world. It would not do to have a whole year go by without “Seismos,” so I will be using flashbacks — ideas and information I have shared with a few people but not with the worldwide TLE readership.

Notes on the history of geophysics in the Ottoman Empire

Abstract. In Anatolia, the history of geophysical sciences may go back to antiquity (600 BC), namely the period when Thales lived in Magnesia (Asia Minor). In the modern sense, geophysics started with geomagnetic works in the 1600s. The period between 1600 and 1800 includes the measurement of magnetic declination, inclination and magnetic field strength. Before these years, there is a little information, such as how to use a compass, in the Kitab-i Bahriye (the Book of Navigation) of Piri Reis, who is one of the most important mariners of the Ottoman Empire. However, this may not mean that magnetic declination was generally understood. The first scientific book relating to geophysics is the book Fuyuzat-i Miknatissiye that was translated by Ibrahim Müteferrika and printed in 1731. The subject of this book is earth's magnetism. There is also information concerning geophysics in the book Cihannuma (Universal Geography) that was written by Katip Celebi and in the book Marifetname written by Ibrahim Hakki Erzurumlu, but these books are only partly geophysical books. In Istanbul the year 1868 is one of the most important for geophysical sciences because an observatory called Rasathane-i Amire was installed in the Pera region of this city. At this observatory the first systematic geophysical observations such as meteorological, seismological and even gravimetrical were made. There have been meteorological records in Anatolia since 1839. These are records of atmospheric temperature, pressure and humidity. In the Ottoman Empire, the science of geophysics is considered as one of the natural sciences along with astronomy, mineralogy, geology, etc., and these sciences are included as a part of physics and chemistry.

Exploration geophysics at China University of Petroleum

China University of Petroleum (CUP) was founded in 1953 and celebrated its 60th anniversary last year in Houston and Beijing, a moment in its history of development. As professor and dean, I was invited to give a luncheon talk at the 83rd Annual International Meeting of SEG in Houston last fall. Now it is worthwhile to sort out a timeline for this history of exploration geophysics at China University of Petroleum. Several universities in China provide exploration-geophysics education, among which China University of Petroleum is unique with all its virtue and merits.

A column on the history and culture of geophysics and science in general

As this is written in early July 2012, I have been around the world a couple of times delivering the SEG Distinguished Instructor Short Course (DISC) titled Seismic Dispersion: A Somewhat Practical Guide to Frequency-dependent Phenomena. The year 2012 also marks exactly 20 years since my first Seismos column appeared in the pages of The Leading Edge. I have found sadly little time of late to write Seismos columns, what with the effort of writing the DISC book in 2010–2011, preparing slides in late 2011 and early 2012 and the actual travel this year to give the course. It is late in the year for a first column of 2012, but here it is.

Review Of Geophysical Applications in Australian archaeology

Multidisciplinary approaches are now commonplace in the investigation of archaeological sites worldwide. Consequently, geophysics has become an increasingly important tool for reconstructing past landscapes and investigating research questions. However, despite their acceptance internationally, in Australia the use of geophysical techniques on archaeological sites has been underutilised. This paper examines the history of archaeological geophysics in Australia and seeks to understand, given their potential advantages, the role that factors such as costs, time, instrument availability and lack of theoretical knowledge have played in the underrepresentation of these methods in local archaeological investigations to date. With the recent introduction of short courses in archaeological geophysics to at least one Australian tertiary institution, this review is a timely overview of where this discipline has been, what it has to offer and whether there is potential for Australian archaeologists to develop the skills necessary to conduct archaeological geophysic investigations, as their international counterparts do already, in the future.