Showing papers on "Longitude published in 1999"

Representing Twentieth-Century Space–Time Climate Variability. Part I: Development of a 1961–90 Mean Monthly Terrestrial Climatology

Abstract: The construction of a 0.5° lat × 0.5° long surface climatology of global land areas, excluding Antarctica, is described. The climatology represents the period 1961–90 and comprises a suite of nine variables: precipitation, wet-day frequency, mean temperature, diurnal temperature range, vapor pressure, sunshine, cloud cover, ground frost frequency, and wind speed. The climate surfaces have been constructed from a new dataset of station 1961–90 climatological normals, numbering between 19 800 (precipitation) and 3615 (wind speed). The station data were interpolated as a function of latitude, longitude, and elevation using thin-plate splines. The accuracy of the interpolations are assessed using cross validation and by comparison with other climatologies. This new climatology represents an advance over earlier published global terrestrial climatologies in that it is strictly constrained to the period 1961–90, describes an extended suite of surface climate variables, explicitly incorporates elevation...

Equatorial currents and transports in the upper central Indian Ocean: Annual cycle and interannual variability

Abstract: The zonal circulation south of Sri Lanka is an important link for the exchange of water between the Bay of Bengal and the Arabian Sea. Results from a first array of three moorings along 80 degrees 30'E north of 4 degrees 10'N from January .1991 to March 1992 were used to investigate the Monsoon Current regime [Schott et al., 1994]. Measurements from a second array of six current meter moorings are presented here. This array was deployed along 80 degrees 30'E between 45'S and 5 degrees N from July 1993 to September 1994 to investigate the annual cycle and interannual variability of the equatorial currents at this longitude. Both sets of moorings contribute to the Indian Ocean current meter array ICM8 of the World Ocean Circulation Experiment. The semiannual equatorial jet (EJ) was showing a large seasonal asymmetry, reaching a monthly mean eastward transport of 35 Sv (1 Sv = 1 x 10(6) m(3) s(-1)) in November 1993, but just 5 Sv in May 1994. The Equatorial Undercurrent (EUC) had a maximum transport of 17 Sv in March to April 1994. Unexpectedly, compared to previous observations and model studies, the EUC was reappearing again in August 1994 at more than 10 Sv transport and was still flowing when the moorings were recovered. In addition, monthly mean ship drifts near the equator are evaluated to support the interpretation of the moored observations. Interannual variability of the EJ in our measurements and ship drift data appears to be related to the variability of the zonal winds and Southern Oscillation Index. The output of a global numerical model (Parallel Ocean Climate Model) driven by the winds for 1993/1994 is used to connect our observations to the larger scale. The model reproduces the EJ asymmetry and shows the existence of the EUC and its reappearance during summer 1994.

Longitudinal variations in planetary wave activity in the equatorial mesosphere

Abstract: Zonal and meridional winds in the equatorial mesosphere and lower thermosphere (65–98 km) measured at two sites separated by 94° in longitude are used to study the zonal structure of planetary-scale waves. The data were obtained with MF radars located at Pontianak (0°N, 109°E)and Christmas Island (2°N, 157°W). The data at Christmas Island were collected from January 1990 to December 1997 and the observations at Pontianak were made from November 1995 to July 1997. Power spectral techniques are used to study the amplitude and frequency variations of long-period oscillations as a function of height and time. A mean climatology of these variations taken from years 1990–1997 is presented. Strong peaks in zonal and meridional winds are found at tidal periods and for the quasi 2-day wave. Zonal spectra exhibit considerable power at periods of 3–10 days, with transient oscillations with periods near 3.5 day and 6.5 days being especially prominent. The 6.5-day wave is particularly strong during April and September. Examination of the phase differences obtained from cross-spectra between the two stations show that the 6.5-day wave is westward propagating with zonal wavenumber 1, while the 3.5 day wave is eastward propagating with wavenumber 1. The 6.5-day wave is identified as a manifestation of an unstable mode, while the 3.5-day wave is identified as an ultrafast Kelvin wave. There are significant longitudinal variations in the amplitudes and inferred momentum fluxes of the 3.5-day wave, amplitudes being larger in the Asian region than in the central Pacific.

Meridional Flows from Ring Diagram Analysis

Abstract: In order to search for meridional circulation in the solar envelope, we have applied ring diagram analysis to a set of small regions over the surface. The helioseismic data consist of Solar Oscillation Investigation/Michelson Doppler Imager Dopplergrams taken over a time span of about 50 hr (~3000 images) on 1998 June 20-22. The regions studied cover 115° in latitude centered on the equator and 30° in longitude. We find poleward flows between r/ R=0.97 and the surface. There is no evidence in this depth range for the return path of these meridional flows. The temporal stability of these flows will be discussed after the analysis of a synoptic map obtained using the same technique.

Gamma-Ray Emission from the Inner Galactic Ridge

Abstract: We present measurements of the 0.05-10 MeV gamma-ray spectra as a function of longitude from the inner Galactic ridge using the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray Observatory. The differential continuum emission relative to intensities at ±10° Galactic latitude appears to be a composite of at least three independent components: a soft low-energy component with a broad longitude distribution and with spectra well approximated by an exponentially absorbed power law; a hard component with a similarly broad longitude distribution modeled by a power law from ~200 keV to 10 MeV with photon index ~-1.75; and strong positron annihilation line and continuum contributions observed toward the center with intensities that decrease rapidly with longitude distance from the center. Although OSSE cannot distinguish between a simple one-component latitude distribution and a more complicated one with, for example, broad and narrow latitude components, an "effective" 5°-6° FWHM Gaussian latitude width gives a spectrum and intensity for the power-law component that agrees with extrapolations of measurements at higher energies using a cosmic-ray interaction model. However, the latitude distribution of the emission is not well measured. Near the Galactic center, bright variable sources contribute significantly to the low-energy spectrum. When account is taken of these variable-source contributions, both the soft low-energy and hard power-law components show a consistent longitude distribution that follows the Galactic matter distribution as evidenced by the Galactic CO distribution. These results, in conjunction with previous measurements, provide new information for determining the Galactic cosmic-ray electron spectrum at lower energies.

Dynamics of the lower thermosphere over South Pole from meteor radar wind measurements

Abstract: A meteor radar was operated at Amundsen-Scott Station, South Pole, from January 19, 1995 through January 26, 1996 and from November 21, 1996 through January 27, 1997. Hourly wind measurements were obtained nearly continuously over these time periods, at an approximate altitude of 95 km and at about 2° latitude from South Pole along the longitude meridians 0°, 90°E, 90°W, and 180°. The scientific advances achieved to date through analyses of these data are presented, including updates to several of our previously published works. The findings addressed herein include the following: (1) Strong divergences of zonal-mean meridional winds occasionally occur over South Pole, implying extreme vertical winds; (2) The monthly mean zonally asymmetric (zonal wavenumber s = 1) wind component varies during the year in a manner consistent with migration of the center of the polar vortex with respect to the geographic (rotational) pole; (3) Strong (>15 m/s) westward-propagating migrating diurnal (s = 1) and non-migrating semidiurnal (s = 1) oscillations exist except during winter months; (4) Long-period (∼2–10 days) waves exist during winter months which are primarily eastward-propagating; (5) Intradiurnal (periods ∼6–11.5 hours) westward-propagating oscillations exist, which are thought to be gravitational normal modes, or “Lamb” waves.

The simulation of the Asian summer monsoon, and its sensitivity to horizontal resolution, in the UK Meteorological Office Unified Model

Abstract: SUMMARY The quality of the simulation of the Asian summer monsoon in the climate version of the UK Meteorological Office's Unified Model, and the impact upon this of increased horizontal resolution, is investigated using two atmosphere-only model runs forced with observed sea surface temperatures (SSTs) and sea ice extents. The runs each cover the period from 1979 to 1988, but have different horizontal resolutions, with one at climate resolution (2.5" latitude by 3.75" longitude, about 300 km at midlatitudes) and the other at global forecast model resolution (0,833" latitude by 1.25" longitude, approximately 100 km at midlatitudes). The characteristic monsoon circulation and the spatial distribution of precipitation are in good agreement with observations. However, the model has a tendency to overestimate the strength of the monsoon, and also exhibits an early monsoon onset. The large-scale interannual variations in circulation appear to be simulated reasonably well (as far as can be determined using this short dataset), although the magnitude of the interannual variability of precipitation is overestimated. However, the regional circulation and precipitation changes between El Niiio and La Niiia years show some significant differences between the model and the observations. The dominant mode of intraseasonal variability seen in both model simulations is, in agreement with observations, associated with the activebreak cycle of the monsoon (although this only explains about 10% of the total variance in both simulations). There is some evidence that the SST changes associated with El Niiio may produce a coherent forcing of the secondary (east-west) mode of intraseasonal variability during the onset phase of the monsoon in the model. However, comparison with observations suggests that this may not be representative of what occurs in the real atmosphere. There is no evidence that the SST variations are causing the system to prefer either the active or the break monsoon phase, as was suggested by Palmer. With increased model horizontal resolution, extra detail is provided in the precipitation distribution, but the mean monsoon simulation is scarcely altered and the systematic emors remain. The interannual variations in circulation and precipitation appear not to be greatly altered, and the overall pattern of intraseasonal variability is also unaffected. This study suggests that the systematic errors in the monsoon simulation are not a result of poor horizontal resolution, but may be due to problems with the model physics.

Thermohaline Structure and Water Masses in the Bering Sea

Abstract: Data from 35,700 hydrographic stations were grouped in areas of 1° latitude and 2° longitude and monthly, seasonal, and annual means calculated. We examined temperature, salinity, and water masses of the Bering Sea, studying their vertical structure, temporal variability, and features of their spatial and temporal distribution. We also considered data from coastal observations, information on the meteorological regime, and river outflow.

Tropical aerosol in the Aleutian High

Abstract: Stratospheric aerosol profiles at high northern latitudes from the Stratospheric Aerosol Measurement (SAM) II experiment are used to document the aerosol maxima that occur in the major wintertime anticyclones. Fourteen years (1978 -1991) of 1 mm extinction are used to calculate median values for each season in bins of 58 latitude by 308 longitude by 1 km altitude. Longitude-altitude sections of estimated surface area density show that tropical, aerosol rich air tends to accumulate in the Aleutian High from 15 to above 30 km, and in the North Atlantic High in the 15-25 km layer. A trajectory case study with winds from the European Center for Medium-Range Weather Forecasting is used to investigate the hypothesis that the observed aerosol maxima are maintained by episodic poleward surges of high aerosol air from the tropical stratospheric reservoir. Lagrangian trajectories are initialized and run backward in time, from both a high- resolution grid and SAM II occultations, for selected days when high aerosol is found in the Aleutian High. Results show that during the case study provided, a deep sheet of aerosol rich air originating over Africa is advected poleward and eastward around the polar vortex and entrained into the Aleutian High.

Longitude structure of ionospheric total electron content at low latitudes measured by the TOPEX/Poseidon satellite

Abstract: The longitude structure of ionospheric total electron content (TEC) at low latitudes has been evaluated using the NASA/Centre Nationale d'Etudes Spatiales TOPEX/Poseidon satellite. The TEC data set is given by the ionospheric range correction, which is computed from TOPEX dual-frequency altimeter measurements. The satellite's orbit allows analysis of vertically measured TEC values at approximately 30° intervals of longitude across the world at local time differences of only 6–12 min. Patterns of longitudinal dependence of the equatorial anomaly were observed during the equinoxes, summers, and winters of 1993, 1994, and 1995. TOPEX observations reveal occurrence of relative maximum anomaly TEC values in the Indian/Asian longitude sector. This dominance in TEC is seen most consistently in the Asian Southern Hemisphere. Also, a relative decrease in anomaly TEC values is evident in the western American region, which is observed primarily during equinox and winter. This configuration of the equatorial anomaly TEC is observed on a day-to-day basis at particular periods of local time. Global theoretical ionospheric model results are presented in an attempt to reproduce the distinctive longitude structure. Variability in E × B vertical drift velocity within specific longitude sectors is shown to be a primary factor in the longitude dependence of equatorial anomaly TEC.

Systems and methods for creating maps using GPS systems

Abstract: A system and method for calculating and storing the location of objects. The system includes a computing device, a global positioning system (GPS) receiver in communication with the computing device, and a range finder in communication with the computing device. The GPS receiver obtains a latitude location and a longitude location of a first position and stores them in the computing device. Next, the GPS receiver obtains a latitude location and a longitude location of a second position and stores them in the computing device. A range finder is then used to locate a distance from the second position to a third position, which is stored in the computing device. The third position is the position of the object for which a location reading is sought. To calculate the latitude and longitude location of the third position, the computing device calculates an azimuth for the third position using the first and second position locations stored in the computing device. Next, the computing device calculates the latitude location and the longitude location of the third position using the latitude location and longitude location of the second position, the distance from the second position to the third position, and the previously calculated azimuth.

Longitudinal structures in lower thermosphere density

Abstract: Thermospheric densities near 200 km from the Satellite Electrostatic Triaxial Accelerometer (SETA) experiment during July and December 1983 are analyzed to reveal two types of longitude structures: (1) the so-called longitude/UT variation which has been noted in higher-altitude satellite data and incorporated into the mass spectrometer incoherent scatter extension-90 (MSISE-90) empirical model [Hedin, 1991] and (2) higher-order structures' in the form of longitudinal wave patterns which have not previously been mentioned in the thermosphere-ionosphere-ionosphere literature. The longitude/UT variation in the SETA densities shares many similarities with that embodied in the MSISE-90 model, except for some differences in symmetry about the equator. Interpretation concerning the origin of the observed variation is handicapped by the Sunsynchronous limitations of the satellite orbit and by the convolution of high-latitude heating effects being mapped into the geographic frame while solar-driven latitudinal variations are mapped into the geomagnetic frame. An unambiguous separation of these effects is not possible with the present orbital constraints. The space-time Fourier analysis method of Salby [1982a, b] is applied in an attempt to quantitatively characterize the higher-order structure in the data. The nature of the satellite sampling introduces ambiguities into the determination of zonal wavenumbers and periodicities. There is evidence of s = 1 and = 2 stationary features, eastward propagating Kelvin waves, and a number of westward propagating waves with zonal wavenumbers s = 0 to = 6 and periods between 6 and 10 hours. Meyer and Forbes [1997] have recently shown the latter class of waves, referred to as Lamb waves in an isothermal nondissipative atmosphere, to represent the preferred response to broadband forcing of the thermosphere. The present observations may represent the existence of Lamb waves in the thermosphere.

Method and apparatus for acquiring position and orientation information

Abstract: PROBLEM TO BE SOLVED: To easily acquire information such as the latitude, the longitude or the like by a system of a low cost by installing latitude and longitude information or the like in a plurality of buildings, and reading the information of the latitude, the longitude or the like nearest to a present position. SOLUTION: Present position information is acquired by installing a plurality of position information display devices for installing latitude and longitude information at a plurality of buildings such as, for example, a pole 20 and reading the information by using a reader from the device nearest to the present position. That is, position information 30 installed on the pole 20 nearest a present place is confirmed. Since the information 30 is latitude and longitude information 340 stored in an IC tag, the information is inputted to a personal computer 10 by using an IC tag reader 150. As a result, a map and the present position are displayed on a display of the computer 10, and present position information can be easily acquired. COPYRIGHT: (C)2000,JPO

Climate Cycles and Climate Transitions as a Response to Astronomical and CO2 Forcings

Abstract: The natural variability of climate occurs on a wide range of time scales, ranging from decades to millions of years. The time scales of importance to the ice ages of the late Cenozoic are of the order of 10 to 1000 ka. On these time scales, the so-called astronomical theory of paleoclimates and in particular its Milan-kovitch version have become the almost universally accepted basis of research (Berger 1992). In its traditional form, the astronomical theory states that changes in high-latitude summer insolation cause the waxing and waning of the continental ice sheets. This was first quantitatively formulated by Milanko-vitch (Berger 1988; Milankovitch 1995), who calculated how the incoming radiation at the top of the atmosphere varies as a function of latitude and the orbital parameters e, ∈ and e sin ῶ, where e denotes the eccentricity of the Earth’s orbit around the Sun, ∈ is the obliquity and e sin ῶ is the precessional effect, with ῶ being the longitude of the perihelion as measured from the moving equinox. Each of the orbital parameters can be expressed as a quasi-periodic function of time. According to the astronomical theory, low summer insolation could prevent the winter snow from melting. The high albedo of snow- and ice-covered areas would initiate a further cooling of the Earth. Eventually, this positive feedback would result in the build-up of the continental ice sheets.

Magnetic impulse events and related Pc1 bursts observed by the Automatic Geophysical Observatories network in Antarctica

Abstract: Magnetic field data obtained by fluxgate and search coil magnetometers installed at four Automatic Geophysical Observatories (AGO Pl, P2, P3, and P4) and at South Pole and McMurdo in Antarctica and at Iqaluit on Baffin Island are used to study the relationship between magnetic impulse events (MIEs) and Pc1 bursts at high geomagnetic latitudes. The spatial scale sizes of MIEs are determined in the investigation of the sources of these events in the magnetosphere. Four MIE events with simultaneous Pc1 bursts are studied. Contour plots of MIE amplitudes show the scale sizes of the examined MIEs to be 5° to 7° in the magnetic latitude direction and 40° to 60° in the magnetic longitude direction. Temporal changes of the ionospheric currents calculated from the fluxgate H- and D-component data indicate that the “convection vortices” associated with the MIEs traveled westward and decayed rapidly. An important finding is that MIE-related Pc1 bursts were observed at higher-latitude (Pl, P4 near 80°) and lower-latitude (P2, P3 near 70°) AGO stations and South Pole Station at 74° with different spectral structures, although the Pc1 spectral power was always a maximum at South Pole Station. These results imply that Pc1 bursts are excited not only in the dayside outer magnetosphere but also in the low-latitude boundary layer region.

Flight system and pseudo sight-forming device for aircraft

Abstract: PROBLEM TO BE SOLVED: To enable a flight according to visual flight rules even under significant weather by responding to each output of a plurality of memories and a detection means, performing an operation so that the topography and obstacle of pseudo sight overlap with those of actual sight which a pilot observes through a display means for displaying pseudo sight. SOLUTION: The coordinates (x, y, and z) of three-dimensional space, the latitude, longitude, and altitude of territorial topography, and the latitude, longitude, and altitude of an obstacle are stored into first, second, and third memories M1, M2, and M3, respectively, as a digital map. A synthesized, three-dimensional map being displayed by a display means 13 has the three-axis information of the latitude, longitude, and altitude for each point, thus allowing the reference of the three axes of the latitude, longitude, and altitude to match, to be displayed superposingly as one screen, and allowing the size of the topography and a building to be displayed by the same measure in superposing processing from the memories M1-M3 using operation circuits. Operation circuits 22-24 are controlled by a control circuit 25.

A fast-moving feature of westward drift

Abstract: he dominant feature in the magnetic declination record at all European sites for which adequate data are available is a minimum between 1750 and 1860. The time of minimum at different sites correlates well with longitude and implies a westward drift rate of 0.61 ± 0.08° yr-1. This is greatly in excess of the widely adopted value of 0.18° yr-1 for global westward drift.

Numerical Prediction of the Summertime Ridge–Trough System over Northeastern Australia

Abstract: The synoptic pattern over northeastern Australia is dominated in the warmer months by a ridge–trough system. Accurate prediction of the location of the system is a significant forecasting problem for regional and global operational models. The regional model that was operational at the time of this study exhibited two significant weaknesses characteristic of many current operational global models, a westward bias in the location of the east coast ridge and errors in the location and strength of the inland trough. The present investigation had three aims:to compute model location errors of the ridge–trough system from a large (6 month, twice daily) dataset of operational forecasts, to explain these errors by evaluating a new regional model, and to confirm the diagnosis using a series of case studies and sensitivity studies. The operational model had a marked mean westward bias of about 2° longitude in the location of both the trough and the ridge. There was a noticeable latitudinal distribution in...

Method for indicating information

Abstract: PROBLEM TO BE SOLVED: To retrieve the course to a specified point quickly and accurately by displaying information for defining the specified point along with information indicative of the latitude and longitude thereof on an information providing medium. SOLUTION: An information column 1 being presented on an information magazine includes a column 6 displaying the latitude and longitude at a specific geographic point in the form of a GPS code in addition to a name display column 2, a contact address display column 3, a still image display column 4, and a comment display column 5. The latitude and longitude display column 6 displays information 7 of 6-7 digit numerals indicating the latitude by degree, minute and second and information 8 of 7-8 digit numerals indicating the longitude. A concrete position is displayed by inputting these numerals to a GPS navigation system. When information indicative of the latitude and longitude at passing points is displayed in combination, a route can also be specified.

Universal timepiece from which latitude and longitude can be determined

Abstract: Disclosed is a universal timepiece from which a latitude and a longitude can be determined A bottom plate (1) which has the names of the main cities in the world, scales and the relative longitudes according to the real longitudes of the cities on the circumference thereof, is included Comprised is a circular hour plate (2) which has a 24-divisional scale having the same angles with respect to the center And a circular star plate (3) which rotates 36099° per 24 hours is included The rotational axis coincides with the Polaris or the south pole and the main stars and a concentric circle for representing the declination are designated in the star plate (3) At each concentric circle, the declination or the value obtained by subtracting the declination from 90° is recorded The clock plate rotates to indicate the time The star plate (3) is the timepiece which rotates in the same velocity with the actual celestial sphere The timepiece of the present invention can be utilized as the universal timepiece and the rotation of the earth can be indirectly observed regardless of day and night The latitude, the longitude and the present time can be advantageously and correctly appreciated

The Highest Solar Wind Velocity in a Polar Region Estimated from IPS Tomography Analysis

Abstract: The Ulysses spacecraft has revealed that the velocity of high-speed solar wind increases with latitude for latitudes > 30° (Woch et al. 1997; Goldstein et al. 1996). We have investigated this velocity increase up to the polar regions using a tomography method from interplanetary scintillation observations made in 1996. For this analysis the tomography method was modified from its previous version (Kojima et al. 1998) so that it has enough sensitivity for the observations at the polar regions, and the reliability and uniqueness of its solution was tested. The modified tomography method analyzes the latitudinal structure in two steps: first the structure within ±80° was derived, and then the latitudes of 80°-90° are analyzed. Synoptic maps of velocity in Carrington longitude and heliographic latitude were derived with the modified tomography method, and latitudinal structures were obtained by averaging velocities along a longitude (Figure 1a). All analysis results show that the velocity increases with latitude in both hemispheres. In Carrington rotations 1911 to 1915, the velocities in the southern polar regions are 100–150 km/s larger than the velocity expected from the extrapolation of the observations at mid-latitudes, while in the northern polar region they were 35–75 km/s larger than the velocities similarly expected from mid-latitude observations. In rotations 1908 to 1911, the velocities in both polar regions were within ±60 km/s of the expected velocity. A large velocity decrease was not seen in the polar regions. At mid-latitudes, the velocity in the northern hemisphere is higher than that in the southern hemisphere.

Discuss the relationship between Mercator sailing and middle latitude sailing

Abstract: In the theory and practice of navigation, we often meet with the calculation of difference of latitude and difference of longitude This paper approves that Mercator sailing actually conforms to middle latitude sailing if we take the shape of the earth as spheroid when calculating difference of longitude

Radio terminal system with longitude latitude measurement function

Abstract: PROBLEM TO BE SOLVED: To obtain a radio terminal system with a longitude latitude measurement function by which position information with higher precision is more effectively utilized. SOLUTION: A system consists of a portable radio terminal 4 that acquires peripheral information at a current position and a base station system that communicates information with the radio terminal 4 through a radio channel. The radio terminal 4 is provided with a longitude latitude measurement means 42 that measures information of current position in terms of longitude latitude and a transmission means 41 that sends the measured information to the base station system. The base station system has a map system 1 that stores the longitude latitude information and peripheral information relating to the longitude latitude, an exchange network 2 that relates the longitude latitude information with the peripheral information and a base station 3 that communicates the information with the radio terminal 4. The radio terminal 4 and the base station systems 1, 2, 3 are cooperated to relate the current position of the radio terminal 4, the longitude latitude information of the current position and the peripheral information to each other in details.

Characteristics of the southern Red Sea earthquake sequences

Abstract: Within the last 30 years, the southern Red Sea has suffered a seven earthquake swarms in: March 1967, November 1988, March 1993, July 1993, May 1994, June 1995 and May 1996 respectively. They were located under the sea between latitudes 14°N and 21°N and longitude 38° to 43°E. June 1995 swarm is the only land activity arc located nearly at latitude 17°N and longitude 43°E. All the southern Red Sea activity occur in a type of swarms each which includes few cycles. Some cycles last for several hours and other last for few days proportionate to the biggest magnitude size in each cycle. Swarms that occurred north of latitude 18°N lasted longer (30 to 60 days) than those occurred south of latitude 17°N (5 to 21 days). Most of the epicenters were located near the eastern wall of the deep axial trough and where the spreading zone is intersected by the NE transform faults. Occurrence of the activities in the form of swarms or sequences is an evidence of their shallow depth. No felt earthquakes were reported in the vicinity of the epicentral area (sea epicenters); due to the local structure, thickness of the salty layers beneath the axial trough and sea water steaming above the sources. The b-value at magnitude range from 3.5 to 6.5 is 0.72 at latitudes 19°N. It increases toward south to be 0.74 at latitude 17°N and 0.92 at latitudes 16°N and it continue increasing toword south to be 1. 1 at latitude 14°N and it reach * ed maximum at latitude 15°N to be 1.3. It is a good indication of the cmstal heterogeneity (structural discontinuities and dislocations) toward the south under the axial trough. Fault plane solutions show general dip strike slip with right lateral along the NE striking nodal plane and few events show normal faulting. The seismogenic layer is limited to a thin layer with thickness of 15 km at depths 6-21 km of the recent oceanic crust under the axial trough.

Longitude and latitude line reading map for gps and navigation system using the map

Abstract: PROBLEM TO BE SOLVED: To provide a map, on which the present position is simply and accurately read from the longitude and the latitude displayed in a digital form, while carrying a GPS(global positioning system) device and to provide a navigation system which utilizes the map and the GPS device. SOLUTION: The map 6 is a waterproofed GPS reading map and has a scale of one-50,000th. On the map, longitude and latitude lines 1 and 2 are written for every ten seconds. Among these lines 1 and 2, only one minute lines are made into distinguished reference lines. If one carries a portable GPS device 5, which digitally displays the longitude and the latitude of a present position by GPS satellites 7, and the map 6, the navigation system reads the present position with the precision better than an actual error of approximately 20 meter square employing the references of the lines 1 and 2 written on the map 6.