An analysis of geomagnetic response functions prior to the Tohoku,Japan earthquake

Geomagnetic records from 20 Japanese observatories have been used to yield time series of response function (RF) components for 20 years at periods of between 2.5 and 60 min. Six observatories showed anomalous variations lasting 3–5 years in the short period part of the above range of periods prior to the March 11, 2011 Tohoku earthquake. The variations could have been intermediate-term precursors. We made a detailed analysis of how noise affects the results using coherence criteria, visual control, and the remote-reference technique. We clarified the conditions that make response functions dependent on geomagnetic activity. For 19 observatories we constructed the tensor of the anomalous magnetic field with Kakioka as the base site. An anomaly in electrical conductivity striking WNW–ESE has been identified beneath the Boso Peninsula near Tokyo in the conditions of strong noise. We sought to corroborate the reality of the anomaly by visual control and processing of nighttime records with minimum noise. We advanced idea that precursors can be monitored using the DC noise field in the presence of a shallow conductivity anomaly. We provided a tectonic interpretation of the obtained RF anomalies. The Boso conductivity anomaly is interpreted as being due to a graben-shaped structure of the sediments and possibly to a deeper plate-tectonics structure, that is, the Sagami Trough. We examine similarities and differences between the Boso anomaly and the Avacha anomaly in Kamchatka, and provided recommendations for further study of the Boso anomaly and for using the Avacha anomaly to monitor EM precursors in Kamchatka.     

DARCY'S LAW AND THE FIELD EQUATIONS OF THE FLOW OF UNDERGROUND FLUIDS

Abstract

Rainfall catches from three standard MKII Meteorological Office gauges are examined. These gauges differ in that one is exposed, one is surrounded by a turf wall and the third is mounted at ground level. Rainfall records between 1976 and 1988 are analysed to assess the variations in rainfall catch between the three types of gauge. During the early period of study, differences between gauges exceeded those in later years and this has been attributed to the settling-in of the new turf wall and ground level collector surfaces. After this initial period the annual differences in catch relative to the standard exposed gauge are 2% and 5% for the turf wall and ground level gauges respectively. Regression analysis has produced correction equations which can convert standard exposed gauge data to either turf wall or ground level equivalents. The equation for ground level/exposed gauges is found to be very similar to one developed in Nigeria and has been found to be applicable to water balance studies elsewhere.     

Periodicities of palaeomagnetic intensity and palaeoclimatic variations: a Walsh spectral approach

The Walsh power spectral technique has been applied to the non-sinusoidal palaeoclimatic (theGloborotalia menardii climatic curve) and palaeomagnetic intensity variation records of the last 1.2 Myr. The analysis reveals, in the case of palaeomagnetic variations, statistically significant peaks (at 90% confidence level) centered around 150, 60 and 24 kyr. The palaeoclimatic spectrum, however, indicates only two significant peaks of 60 and 24 kyr. The identical periodicities in both the phenomena may suggest a causal link between the geomagnetic intensity variations and climatic changes.     

Cloudiness and sunshine duration measurements in the U.A.R.

Summary Seasonal variations of cloudiness have been studied for the different zones of the United Arab Republic. It was found to be very low and to decrease more towards lower latitudes.From the records of a Campbell Stokes Sunshine recorder, installed at the Agro-meteorological Station at Giza, during a period of six years from 1956 to 1961, the monthly and daily variations of the hours of sunshine duration, have been also studied in detail and presented in a practical form.     

Periodicities in natural remanent magnetization and palaeoclimatic records detected by walsh spectra

The time series consisting of nonsinusoidal Natural Remanent Magnetization (NRM) and palaeoclimatic variations for the past two million years have been spectrally examined by using a new Walsh transform technique. The results show statistically significant periodicities (at 95% confidence level) of approximately 92,000 years; 43,000 years and 21,000 years in the ensemble spectra of the NRM intensity (mineralogic) variations. These NRM periodicities are remarkably close to the well-known Milankovitch cycles. The ensemble spectra of palaeoclimatic records reveal only 41,000 years statistically significant (95%) periodicity corresponding to the obliquity cycle. The study suggests that NRM variations in deep sea sediments probably are more sensitive recorders of palaeoclimatic memory than the oxygen isotope variations.     

近1800年来云南洱海流域气候变化与人类活动的湖泊沉积记录

对云南洱海湖泊岩芯沉积物进行了多环境指标（年代学、色素、硅藻、有机碳稳定同位素、磁化率、化学元素）的分析,建立了近１８００年来云南洱海流域气候与环境变化的序列,气候演化具有暖干、冷湿交替的组合呈些特征气候阶段如中世纪温暖期、小冰期气候特征在洱海源泊沉积记录中均有反映,洱海湖泊上沉积记录的气候暖干－冷湿交替变化规律,反映了西南委风影响下的气候演化特征,湖泊沉积记录中包含丰富的人类以的信息,磁化率,元     

Space-time analysis of the relative local secular variations of the geomagnetic field (1966–2005) along the Zgorzelec-Wiżajny profile

The Zgorzelec-Wiżajny profile cuts through the main European geotectonic units of the Palaeozoic Western and Central European Platform and the East European Craton, including the connecting Trans-European Suture Zone. The paper summarises 40 years of research on geomagnetic secular variations along the Zgorzelec-Wiżajny profile since 1966. It discusses methods of processing measurement records and presenting their results. The latter are presented against the background of the local geology and the crustal deep magnetic structure data. The hitherto method of variation analysis was modified to address a new trend in the geomagnetic secular variations that has emerged in the East European Craton during the last five years (2001–2005).     

Secular variations in the geomagnetic field in St. Petersburg and the adjacent area from historical data, 1630–1930

Geomagnetic field parameters have been measured in different sites of the northwest of Russia for hundreds of years. This work presents the results of numerous measurements in St. Petersburg, as well as in the Gulf of Finland within the zone from 25° to 30°30′ E and from 59° to 61° N. The first measurements were made in the period1630–1650. For this work, archival data, provided by the Archives of the St. Petersburg Magnetic Observatory (SPbF IZMIRAN), and data from different historical records have been used. Data on the Earth’s magnetic field variations in St. Petersburg have been recorded since 1726; they were analyzed and corrected to get a uniform and complete data set. The reconstructed long-term data set of magnetic variation measurements in St. Petersburg was compared with the GUFM1 historical model. This model allows us to calculate the values of all parameters of the main magnetic field in any place on the Earth since 1590. The comparative analysis carried out by us has revealed a discrepancy between the model and measured values. This discrepancy can be caused by local secular variations in the magnetic field in the St. Petersburg region. The correction of the area-averaged secular variation makes this discrepancy insignificant.     

Towards a high-resolution,global, deep-sea chronology for the last 750,000 years

Variations in the ratio of¹⁸O/¹⁶O as measured in shells of marine calcareous microfossils are primarily dominated by changes in global ice volume; hence these variations provide a set of global time lines in deep-sea sediments. It is likely that the timing of major changes in oxygen isotope values is strongly influenced, if not controlled, by variations in the geometry of the Earth's orbit. Since the variation of orbital parameters can be accurately calculated, the opportunity exists for transforming this orbital chronology into a geological chronology.Through careful correlation of oxygen isotope records in a set of deep-sea cores from the sub-Antarctic, South Atlantic and equatorial Pacific, we have assembled a composite isotopic section spanning the last 750,000 years with an average sedimentation rate of 2.3 cm/1000 years. A new chronology for this time period was developed by adjusting the ages of the oxygen isotope stage boundaries in this composite section so as to extend the consistent phase relationships that exist between variations in oxygen isotope ratios and changes in obliquity and precession during the last 300,000 years to the entire 750,000-year record. Previously identified difficulties in phase locking precession with the filtered isotopic signal between 365,000 and 465,000 years B.P. have been resolved with the recognition that precessional variations have an average period of 19,000 years and not 23,000 years during this interval. Since this new age model yields the best match between variations in obliquity and precession and their corresponding frequency components in the oxygen isotope record, we believe that it presents the most accurate chronology yet developed for deep-sea sediments.With this new age model providing the time control, power spectral analyses of South Atlantic and sub-Antarctic chemical and biotic indices show that there is a strong tendency for variance to be concentrated at frequencies corresponding to periods of ～ 100,000, 41,000 and 23,000 years.     

On the existence of the east-west asymmetry in the optical observations of the solar corona

The east-west asymmetry has been analyzed using the 1946–2000 corona observation data for the green line at the Kislovodsk station. A positive east-west asymmetry has been revealed throughout the entire observation period except for three years, 1994–1996. Time variations of the east-west asymmetry for certain periods coincide with those for flares. Seasonal variations of the east-west asymmetry revealed earlier by other authors are not confirmed. If seasonal variations of the east-west asymmetry in the corona exist, their amplitudes are smaller than or comparable to the instrumental errors, errors caused by atmospheric variations during the observation period and to differences between the corona-intensity measuring systems used at different observatories.     

Problem of the nature of the sunrise effect in diurnal variations in the electric field in Kamchatka: 1. Time variations in the electric field

The effect of sunrise in time variations in the electric field in the near-Earth atmosphere at the Kamchatka Paratunka observatory has been studied. Twenty-nine records under fair-weather conditions have been selected. It has been indicated that the estimated effect parameters—the times of the effect’s onset and field strength maximum relative to the sunrise time, as well as the ratio of the strength maximum to its value before sunrise and the effect duration—coincide with the previously published data. Thereby, the conclusion is confirmed that the sunrise effect in diurnal variations in the electric field in the near-Earth atmosphere is related to the turbulence and convection processes in the atmospheric boundary layer at a change in atmospheric temperature.     

Recent changes in the level of Lake Abiyata,central main Ethiopian Rift

Abstract

The spatial and temporal variations in the level of Lake Abiyata and controlling natural and manmade factors are presented. This study has been made by combining evidence from hydrometeorological and lake level records, water budget analyses, aerial photograph and satellite imagery interpretations, and numerical groundwater flow modelling. The most important components of the water balance of the lake are precipitation, river inflow and evaporation. The lake level has been fluctuating considerably over a wide range (by 6 m during the last 60 years) strongly controlled by the precipitation trends in the adjacent highlands. Climatic changes and consequent reduction in the surface water inputs have resulted in the reduction of its size. Recent abstraction of water for irrigation and soda ash production have drastically changed both the lake level and its hydrochemistry. This change appears to have grave environmental consequences on the fragile rift lacustrine ecosystem.     

Asymmetry of the contours of the Fe X 6374-Å coronal line

The east-west asymmetry has been analyzed using the 1946–2000 corona observation data for the green line at the Kislovodsk station. A positive east-west asymmetry has been revealed throughout the entire observation period except for three years, 1994–1996. Time variations of the east-west asymmetry for certain periods coincide with those for flares. Seasonal variations of the east-west asymmetry revealed earlier by other authors are not confirmed. If seasonal variations of the east-west asymmetry in the corona exist, their amplitudes are smaller than or comparable to the instrumental errors, errors caused by atmospheric variations during the observation period and to differences between the corona-intensity measuring systems used at different observatories.     

Preface to the special issue on complicated features on seismic sources and deep structures

Earthquake is a kind of natural phenomenon in the Earth.Earthquake seismology has been developed quickly since modern digital seismometers were applied to observations.From seismic records,seismologists study source properties of the earthquakes and detect multi-scale structural variations in the crust,mantle,and core.     

Variations in tree ring stable isotope records from northern Finland and their possible connection to solar activity

Within a project on climate in Europe during the past few hundred years we have collected a record on stable isotope ratios ¹³C/¹²C and ¹⁸O/¹⁶O in tree ring cellulose from pine trees in northern Finland. The records cover the time interval 1600–2002 AD and have an annual time resolution. The carbon stable isotope record from northernmost Finland correlates quite strongly with local growth period temperature. Statistical analysis of the carbon and oxygen stable isotope records reveals variations in the periods around 100, 11 and 3 years. A century scale connection between the ¹³C/¹²C record and solar activity is most evident. These results based on stable isotope records support previous evidences of a centennial solar-climatic link obtained for northern Finland using tree ring data.     

Secular variation in aerosol transparency of the atmosphere as the possible link between long-term variations in solar activity and climate

Information about variations in solar activity and climate on the time intervals from 130 years to four–five last centuries, including results of instrumental measurements (Wolf numbers, actinometry, thermometry) and indirect indicators (ice core acidity, NO ₃ ^? ion concentration in polar ice, temperature tree-ring reconstructions), has been analyzed for the Northern Hemisphere and its high-latitude part. It has been obtained that the observed relation between secular variations in solar activity and near-Earth temperature resulted from the effect of the corresponding variation in aerosol transparency of the stratosphere on terrestrial climate. It has been also indicated that long-term variations in the aerosol content of the stratosphere can, in turn, be related to secular cycles in atmospheric ionization caused by variations in fluxes of ionizing cosmic particles.     

Behaviour of the earth's magnetic field as recorded in the sediment of Loch Lomond

A palaeomagnetic record of geomagnetic secular variation during the last 7000 years has been obtained from the sediments of Loch Lomond, Scotland. The magnetic direction fluctuations repeat well between cores and show greater detail, especially over the last 5000 years, than other European records. A time scale has been derived from¹⁴C analyses on the Lomond sediment and comparison with other¹⁴C-dated sediments. Investigation of relative palaeointensity determination methods has shown that the widely used normalization parameter of partial ARM is insensitive to even small sediment grain size fluctuations.The new high-fidelity direction record and improved time scale show that geomagnetic field changes have not followed a simple oscillatory pattern during the last 7000 years. The record enhances the application of palaeomagnetism to dating recent sediments, as the main declination swings are now characterized by fine detail, and paired inclination data are also available. The problem of mismatching swings when correlating with other paired directional records is thus reduced.The palaeomagnetic record agrees well with some archaeomagnetic results. It confirms the period of anticlockwise motion of the geomagnetic field vector, between 1000 and 600 years B.P., which was first documented by English archaeomagnetic investigations. Clockwise motion is shown to predominate during the remainder of the last 5500 years. The VGP path does not correlate with that of Japanese archaeomagnetic results nor North American sediment data from 2000 to 0 years B.P. This suggests that the secular changes are dominated by local non-dipole sources rather than wobbling of the main geomagnetic dipole.     

Excursions of the Pleistocene geomagnetic field recorded in Gulf of Mexico sediments

The detrital remanent magnetism of a series of deep-sea sediment cores from the Gulf of Mexico has been measured. Together with microfaunal analysis, the data show that excursions of the geomagnetic field occurred at 17,000 ± 1500years B.P. and32,000 ± 1500 years B.P. It is suggested that the former may be the Laschamp excursion and that the latter may be the Lake Mungo excursion. No similar geomagnetic behavior is detected for the past 50,000 years. Sedimentation rates as high as 19 cm per 1000 years are indicated.Susceptibility (χ) maxima in the cores are due to tephra layers. Correlation between the intensity of magnetization (J) and χ shows that variations of intensity are more a function of ferrimagnetic mineral concentrations than geomagnetic field intensity variations.     

Electric and electromagnetic processes in the near-Earth atmosphere before earthquakes on Kamchatka

Simultaneous records of the diurnal variations in the quasistatic electric field in the near-Earth atmosphere, fluxes of discrete electromagnetic pulses in the VLF band, source azimuths, narrowband filter output emission intensity at frequencies of 4.65 and 5.3 kHz, and time forms and spectra of VLF pulses have been analyzed. The anomalous behavior of these parameters in October 2002 and August 2004 with different time delay was accompanied by earthquakes near the southeastern coast of Kamchatka at distances of 250–400 km from the registration points. Based on the results of a fine frequency-time analysis of the broadband records of VLF signals, it has been indicated for the first time that discrete electromagnetic pulses observed in anomalous fluxes before earthquakes were signals of local thunderstorm processes.