bluuebunny/crossref_metadata_2025 huggingface dataset:
An automatic magnetic observatory system
Authors: Andersen F
Published: March 2017

A digitally recording magnetometer system is designed to replace the standard photographie magnetographs at geomagnetic observatories. The instrument can operate for up to 80 days without attention. Provision is made for immunity to brief power failures. The
elements D, H, and Z are derived from a 3-component fluxgate magnetometer in which ail three detectors operate in near-zero field. A simple proton magnetometer measures F. Voltages proportional to the values of the three elements D, H, and Z are sampled in quick succession by a digital voltmeter,
once per minute. Each minute, a measurement of Fis also made. The four measurements are recorded in digital magnetic tape. Each ten minutes, the date, time, and station identification are also recorded. A strip-chart recorder produces a visual indication of the variations in D, H, and Z. The
performance of the system is estimated from a comparison of hourly mean values with those of the St. John's Magnetic Observatory.
Gravity measurements in northern District of Keewatin and parts of District of Mackenzie and District of Franklin, N.W.T.
Authors: Gibb R A , Halliday D W
Published: March 2017

Ten Bouguer anomaly maps (1 :500,000) covering a large part of the Churchill structural province of the Canadian Shield to the north and northwest of Hudson Bay were compiled from a total of 3,698 gravity stations. There is a correlation between positive gravity
anomalies and granulite terrains on Boothia and Melville peninsulas. Continuity of a zone of anomalously dense crust from Baker Lake to Southampton Island and perhaps as far east as Coats Island is inferred from an easterly alignment of positive gravity anomalies. This zone is expressed at the
surface by high grade metamorphic terrains intruded locally by anorthosite and gabbro. In the Ogden Bay region the correlation between gravity anomalies and granulites is not so clear. Major negative gravity anomalies are related to granitic plutons which lie within a broad regional gravity low
extending from north of Baker Lake to Melville Peninsula. Although there is also a general correlation in trend and location between major Aphebian fold belts and this broad regional gravity low there is generally little correlation between individual fold belts and the gravity
anomalies.
Canadian Geothermal Data Collection - northern wells 1976-77
Authors: Taylor A E , Judge A S
Published: March 2017

The assessment and solution of many problems which may occur in the development of northern regions require a knowledge of subsurface temperatures. This volume supplements three earlier vol\.Utles in this series, and it reports new measurements at 37 of the sites
listed in the previous vol\.Utles and observations from 8 new sites. A total of 86 determinations of permafrost thickness have been reported in the collection to date. Determined thicknesses in the Arctic Islands range from 144 m to 728 m, in the Mackenzie Delta from 0 m to 700 m and in the
remainder of the Northern Mainland from 0 m to in excess of 700 m.
Temperatures and Heat Flow in a System of Cylindrical Symmetry Including a Phase Boundary
Authors: Taylor A E
Published: March 2017

A numerical model has been developed to simulate the transient thermal regime arising from a cylindrically symmetric disturbance in a semi-infinite medium. Heat transfer by radial conduction only is considered and provision is made for a phase change involving
latent heat to occur within the medium. The program has been used to produce a set of tables giving both temperatures at various distances from the source for a range of dimensionless times and the radial heat flow leaving the source region. Data are tabulated for cases with and without a phase
change; in the case of a phase change, tables are given for a latent heat density of 30 MJ/m3 and several source and initial temperatures. The source disturbance is considered to be either sustained indefinitely or to last for a finite period, after which cooling occurs. The program finds
application in such geophysical problems as the study of the disturbance to the geothermal regime resulting from the drilling of and production from petroleum wells, from buried pipelines and power cables and from underground tunnels. Using the tables, a hypothetical example is developed to
illustrate the thermal disturbance arising from drilling a petroleum exploration well through permafrost.
Canadian Seismograph Operations - 1976
Authors: Halliday R J , Lombardo F , Schieman D , Shannon W E
Published: March 2017

During 1976 the Division of Seismology and Geothennal Studies of the Earth Physics Branch, Department of Energy, Mines and Resources operated or contracted the operation of 20 standard seismograph stations, 14 regional stations, 2 telemetered networks based at
Ottawa and Victoria, a medium aperture array at Yellowknife, a strong-motion seismograph network on the West Coast and several special or temporary seismographs. This report gives the characteristics of the various systems and describes the format and availability of the recorded
data.
The gravity field of the Central Labrador Trough, northern Quebec
Authors: Kearey P , Halliday D W
Published: March 2017

The Labrador Trough is the best preserved and exposed of a series of Aphebian (lower Proterozoic) fold belts which surround the Archaean Un gava Craton of northern Quebec and mark the junction of the Superior and Churchill Structural Provinces in this region. The
results of a detailed gravity survey of the central Labrador Trough are presented. Regional gravity profiles across the Labrador Trough are characterized by a field which decreases gradually to the east over the Superior Province, reaches a minimum beneath the Trough and thence increases rapidly
over the Churchill Province to attain a mean level some 15 mgal higher than observed over the Superior Province. This regional field may be interpreted in terms of a relatively elevated Conrad discontinuity beneath the Churchill Province isostatically compensated by a thickened lower crust. The
model is consistent with basement reactivation of the Churchill Province following collision with the Superior Province during the Hudsonian Orogeny. Subtraction of the regional field from the observed gravity data reveals that positive residual anomalies over the eastern part of the Labrador Trough
correlate with outcrops of basic meta-igneous rocks. Their causative bodies probably dip to the east and extend to maximum depths of 9 km in the central part of the area. These interpreted depths are considerably less than previous estimates based on geological analysis. Small positive anomalies
correlate with iron formation. A persistent depression in the observed gravity field over the centre of the Labrador Trough in the south coincides with thick deposits of the basal continental sedimentary unit. In the northern part of the area the causative bodies of the negative anomalies are
probably elevated areas of granitic basement. These elevated basement features may be related to a ridge that controlled sedimentation during much of the Trough's history. The geological history and present structure of the Labrador Trough may be related to a sequence of events involving the closure
of a small ocean dividing the Superior and Churchill Provinces in Aphebian times culminating in their collision during the Hudsonian Orogeny.
Canadian earthquakes 1976
Authors: Horner R B , Wetmiller R J
Published: March 2017

This catalogue lists more than fourteen hundred earthquakes, rockbursts and possible or confirmed blasts in Canada and adjacent areas detected by the Canadian seismograph network in 1976. A total of 497 events are located, 371 in Canada and 126 in adjacent areas
of the Unined States and Greenland. Fifty-nine earthquakes in or near Canada had a magnitude of 4 or greater, including eight with magnitude 5 and two with magnitude 6. The largest earthquake in or near Canada in 1976 occurred west of Vancouver Island on 20 December and had a magnitude of Ms 6.7.
More than nine hundred additional small shocks are described only by magnitude and by distance from the nearest seismograph station. Most earthquakes in Canada in 1976 occurred west of Vancouver Island, in the northern Yukon, on Baffin Island and in the Queen Elizabeth Islands. Nineteen earthquakes
were reported felt in Canada in 1976. The most strongly felt earthquake occurred on 16 May near Pender Island, B.C. and was felt with maximum intensity VI in several localities in southwestern British Columbia. As well an earthquake on 23 October near Saint-Siméon, P.Q., was felt with maximum
intensity V in southern Quebec. The text is accompanied by four epicentre maps and by isoseismal or intensity maps for five of the felt earthquakes. In addition the located events are listed chronologically by region in four tables; the unlocated events are listed chronologically by station code in
29 tables. Reports of earthquakes felt in Canada are summarized in one table. Histograms show the distribution of epicentral distances from nine stations recording many unlocated events. Focal mechanism solutions for six earthquakes in 1976 are shown in one figure and described in one
table.
Canadian earthquakes - 1977
Authors: Horner R B , Stevens A E , Wetmiller R J
Published: March 2017

This catalogue lists 525 earthquakes that occurred in Canada and adjacent areas of the United States and Greenland during 1977. A total of 387 events are located in Canada or off its coasts, including 16 of magnitude 4 or greater. The largest earthquake in this
catalogue, magnitude ML 4.9, occurred on 22 April 03h in the Arctic Ocean northeast of Greenland. The largest earthquake in Canada in 1977, magnitude ML 4.6, occurred on 19 July 17h in the northern Queen Charlotte Islands, B.C. Most earthquakes in Canada in 1977 occurred west of Vancouver Island, in
extreme southwestern British Columbia, the northern Yukon Territory and the central Queen Elizabeth Islands, N.W.T. Minor activity was observed in western Alberta, the eastern Arctic, southwestern Québec and along the St. Lawrence Valley. Thirteen earthquakes were reported felt in Canada in
1977. The most widely and strongly felt occurred on 08 August 23h in the lower St. Lawrence River and were felt to distances of 200 km with a maximum intensity of IV near the epicentre. The located earthquakes are listed chronologically by region in four tables following the text and are plotted on
five epicentre maps. Reports of earthquakes felt in Canada in 1977 are summarized in one table. Maps of intensities are presented for two of these earthquakes.
Canadian earthquakes - 1978
Authors: Horner R B , Stevens A E , Wetmiller R J
Published: March 2017

Le présent catalogue énumère 226 tremblements de terre de magnitude égale ou supérieure à 3.0 qui se sont produits au Canada et dans les régions avoisinantes des États-Unis et du Groenland au cours de 1978. Il y eut 160
séismes au Canada ou au large de ses côtes, dont 33 de magnitude supérieure ou égale à 4 et cinq de magnitude supérieure à 5, ces derniers à l'ouest de la terre ferme de la Colombie-Britannique. Le plus grand tremblement de terre dans ce catalogue, magnitude
Mg 6.1, est survenu le 11 juin à 14h à l'ouest de l'île Vancouver. La plupart des tremblements de terre au Canada en 1978 sont situés à l'ouest de l'île Vancouver, dans la région frontalière de l'Alaska, du Yukon et de la Colombie-Britannique, dans le nord du
territoire du Yukon, dans la partie occidentale des îles Reine-Elisabeth, dans la baie Baffin et sur l'île Baffin, T.N.-0. Des séismes moins fréquents ont eu lieu dans l'ouest de l'Alberta, dans le sud-ouest du Québec et le long de la vallée du Saint-Laurent. En 1978,
on a rapporté 28 tremblements de terre ressentis au Canada dont sept de magnitude inférieure à 3.0, six d'entre eux au Québec et un en Ontario. Les 21 plus grands séismes ressentis au Canada se sont répartis connne suit: Colombie-Britannique (10), Québec (6),
Alberta (1), Saskatchewan (1), Territoire du Yukon (1) et l'État de Washington (2). Les tremblements de terre les plus fortement et les plus largement ressentis se sont produits dans le nord de l'île Vancouver le 02 juin à 20h et le 25 juillet à 23h. Ils ont atteint une
intensité de V à proximité de l'épicentre. On les a perçus jusqu'à des distances de 200 km. Dans le cas de quatre autres tremblements de terre, on a remarqué les effets reliés à une intensité maximale de V: celui du 11 juillet à 02h près
des îles Reine-Charlotte, du 19 août à Olh et du 23 août à 10h près du sud de l'île Vancouver et du 18 février à 14h dans le sud-ouest du Québec. Les tremblements de terre localisés sont classés par ordre chronologique et selon la
région d'origine; ils apparaissent dans quatre tableaux ajoutés à la fin du texte et sont tracés sur sept cartes d'épicentres. Un autre tableau résume les tremblements de terre rapportés ressentis au Canada en 1978. Pour huit d'entre eux, on donne une carte des
intensités. En plus des grands séismes que l'on vient de mentionner, on a tracé sur les cartes et catalogué sur bande magnétique les données d'épicentre et de magnitude d'environ 500 tremblements de terre de magnitude inférieure à 3.0, localisés au
Canada et dans les régions avoisinantes durant l'année 1978.
Canadian seismograph operations - 1978
Authors: Halliday R J , Lombardo F , Schieman D , Shannon W E
Published: March 2017

At the end of 1978 the Division of Seismology and Geothermal Studies of the Earth Physics Branch, Department of Energy, Mines and Resources operated or contracted the operation of 19 standard seismograph stations, 23 regional stations, 2 telemetered networks
based at Ottawa and Sidney, B.C . , a medium aperture array at Yellowknife , a strong-motion seismograph network on the West Coast and several special or temporary seismographs. This report gives the characteristics of the various systems and describes the format and availability of the recorded
data.
Geomagnetic surveys at West Hawk Lake, Manitoba, Canada
Authors: Clark J F
Published: March 2017

West Hawk Lake - Lat. 49 . 7°N, Long. 95 . 2oW - is a near-circular structure of impact origin . A contour map of magnetic total intensity (F) has been compiled from observations at 225 stations on the land surrounding the lake and about 300 stations over
the lake in summer and winter. The contours have a circular form centered on the lake with a main low in F over the southern part of the lake and a secondary low over a northern sector. A comparison of F values obtained from an aeromagnetic survey of the area and the surface data indicates contour
patterns and gradients consistent with an asymmetrical meteoritic crater whose diameter is 2.5 + 0.2 km. Values of near-surface apparent resistivity measured close to the rim and shoreline are low (~ 100 ohm-m) but increase rapidly to about 8,500 ohm-m a few km outside the
rim.
A three-component aeromagnetic survey of the Nordic Countries and the Greenland Sea
Authors: Hannaford W , Haines G V
Published: March 2017

In 1965 the Dominion Observatory 's airborne magnetometer surveyed Iceland, northem Greenland , the Greenland Sea, and also Denmark, Norway, Sweden and Finland. The survey was sponsored jointly by Canada and the four countries of northem Europe. A gyro-stabilized
fluxgate magnetometer recorded the three geomagnetic elements D, H and Z in continuous analog form and also produced averages computed over 5-minute intervals of time. Total intensity F was measured by a proton precession magnetometer. Corrections for the magnetic field of the aircraft, determined
from six calibration 'swing' flights, were applied to the observations, and a 3rd degree polynomial was fitted to the results. The residuals revealed that throughout many survey flights the aircraft's magnetism differed considerably from the mode which was prevalent during calibration swings.
Residual-derived estimates of the aircraft field error peculiar to each flight indicated several distinct modes of aircraft magnetism, and the data were corrected accordingly. A comparison of observations at 70 flight path intersections yielded standard errors of 0.39° in D, 57 -y in H, 42 -y
in Z and 37 -y in F, for the 5-minute averages over northem Europe and the Greenland Sea. Corresponding standard errors in the Iceland area were estimated at 0.42° in D, 86 -y in H, 52 -y in Z and 52 -y in F.
Gravity surveys in the Alexandria area, eastern Ontario
Authors: Sobczak L W
Published: March 2017

The results of 1700 gravity observations completed by the Dominion Observatory from 1945 to 1964 are presented in the form of a Bouguer anomaly map. Seven profiles are analyzed. The Bouguer anomalies are correlated with magnetic and geological information and the
interpretation of the gravity datais based on rock density measurements. Two maps showing the compu ted first and second vertical derivatives of gravity are also presented. Negative Bouguer anomalies are correlated with the Chatham-Grenville syenite stock and a similar intrusion at Mount Rigaud on
the southern border of the Grenville-A subprovince. lt is postulated that the negative anomaly near Plaisance indicates the presence of a sirtlilar intrusion below the Paleozoic cover. The Alexandria High, a positive residual Bouguer anomaly which extends Crom Lunenburg to Pointe-au-Chêne, may
be explained by the presence of a basic lenticular body of thickness varying Crom 6000 to 9000 feet and width of 50,000 feet at a depth varying from 3000 to 5000 feet. The approximate thickness of the Grenville Series is 11,000 to 12,000 feet along the crest of the Alexandria High. The regional
gravity gradient which increases from -30 mgal in the northwest to +10 mgal in the southeast of the area is correlated with arise of over 3 kilometres (10,000 feet) of the Mohorovicic discontinuity.
Results of underwater gravity surveys over the Nova Scotia Continental Shelf
Authors: Stephens L E , Goodacre A K , Cooper R V
Published: March 2017

During the summer of 1970, 692 underwater gravity stations were established on the Atlantic continental shelf of Canada. The areas surveyed include the Laurentian Channel, Cabot Strait, and parts of Saint Pierre Bank and the Scotia Shelf. Stations were located on
a 15-km grid and detailed profiles were made across the Orpheus anomaly and across a diapiric structure north of Sable Island. During three cruises of the CNA V Sackville, Decca and radar were used as primary navigation aids. The gravity data are presented as a Bouguer anomaly map. The anomalies
generally strike in an easter ly direction across the continental shelf. The dominant feature is the linear Orpheus anomaly which extends 250 km eastwards from Chedabucto Bay and is flanked to both north and south by positive anomalies. The Orpheus anomaly is probably caused by Carboniferous and
younger sedimentary rocks whereon both flanking anomalies appear to be related to Proterozoic metavolcanic rocks with interspersed Devonian basic intrusions. A broad negative anomaly south of the Orpheus anomaly is probably underlain by a Devonian granite batholith. Between the Miquelon Islands and
Cape Breton Island, a broad arcuate positive anomaly partly coincides with a Carboniferous basin delineated by seismic surveys. This high is attributed to dense, shallow structures within the pre-Carboniferous basement. The Laurentian Channel is a major structural feature which displaces and
distorts the dominant easterly trends of several linear anomalies including the Orpheus anomaly.
The estimation of seismic risk in Canada - a review
Authors: Whitham K , Hasegawa H S
Published: March 2017

Progress and problems in the estimation of seismic risk in Canada are reviewed, with some emphasis on the uncertainties in the different approaches which have been tried. There is no adequate neotectonic framework for Canadian seismicity generally, and this is
the key factor which is inhibiting more accurate delineation and expression of seismic risk in national codes. However, some progress in understanding the tectonic framework is being made, particularly in western Canada. The present national building code formulation of seismic risk needs to be
updated with better seismic strong motion information: the range of validity of any expressions used should not be exceeded, and users should beware over-simplification and understatement of error. In particular users should understand that the expression of seismic risk by exceedance estimates of
one (or even two) simple peak motion parameters is physically a gross approximation. Risk formulation for specific sites for critical structures can be made more conservatively than for the national building code within a very approximate tectonic framework: an approach using design earthquakes is
necessary. In general it can be shown that the results cannot be compared at very low risk levels with calculations based on extrapolation of the national building code method. This is because the sta tistical extreme value mode! is being extended beyond its range of validity. Geophysical judgments
cannot be avoided in the design earthquake approach and some, at least, of these are essentially non-quantifiable. Sorne progress is being made in understanding the seismological factors that enter into the time history of ground motion as seen in strong motion records. Better strong motion
empirical deterministic and statistical relationships are known now than in the past, and the Fourier spectrum approach is suggesting ways in which the average response spectrum approach can best be modified to suit local conditions. Much remains to be accomplished including the comparison of
theoretical predictions of eastern Canadian strong motion data with actual data, once it is acquired. Once again, the users of an average response spectrum approach to design need to understand how the average adopted depends upon the sclection criteria adopted by the spectrum
proponent.
Microseismic noise on Canadian seismograph records in 1962 and station capabilities
Authors: Basham P W , Whitham K
Published: March 2017

Measurements of short- and long-period microseisms from the eight first-order Canadian seismic stations in operation during 1962 are presented. Monthly mean values of specific-hour and daily maximum short- and long-period amplitudes vary considerably from station
to station and from season to season. Also presented are cumulative-frequency plots and amplitude-probability levels of specific-hour and daily maximum short-period microseismic amplitudes. Long-period microseismic periods and spectral-peak positions are seen to vary from summer to winter.
Curves are presented illustrating the 90-per-cent and 50-per-cent probability levels of unified-magnitude perceptibility for epicentral distances up to no degrees and the 90-per-cent probability level of local-earthquake magnitude perceptibility for epicentral distances up to 20 degrees. These
curves are used to explain an easily demonstrated station variability in teleseism reporting and to assess the theoretical coverage of Canadian seismicity for 1962.
Earthquakes of eastern Canada and adjacent areas, 1928-1959
Authors: Smith W E T
Published: March 2017

This is the second in a series of papers intended to describe the entire known earthquake history of eastern Canada. The area considered embraces northeastern North America and its adjacent waters east of longitude 85° W and bounded by the 40th and 60th
parallels.
The two lists in the earlier paper, one of earthquakes in eastern Canada and the other of those in the northeastern United States, have been continued. From 1928 to 1959 there were 405 shocks in eastern Canada and 312 in the northeastern United States. To 1959 the shocks total 743 in the Canadian
lists and 729 in the United States lists. Each list is accompanied by a geographical index.
Either an intensity or a magnitude has been assigned to each shock, and a linear relation between these scales has been accepted. All earthquakes are shown on the maps by symbols proportional to their sizes regardless of the scale on which these sizes are expressed. lsoseismal maps of six of the
larger earthquakes have been included.
In general, only essential information about each shock is given, but a number of the Canadian entries are annotated and striking or unusual features of all the important shocks have been included. After each entry in the text all the sources of information consulted are indicated by letters and
numbers, which can be readily identified in the references.
Magnetic charts of Canada for Epoch 1965.0
Authors: Dawson E , Dalgetty L C
Published: March 2017

Magnetic charts of Canada in components D, I, H, Z, F, X, Y, G, U, V and their annual changes were drawn for epoch 1965.0. Charts were compiled from some 18,000 observations in D, H, Z, acquircd since 1947. Seventy-five percent of thesc were airborne data. The
observatory and repeat station network, neressary for reduction of data to epoch, is described. Machine processing techniques are used. Charts are drawn using average values computed over an equal area grid, a unit grid being equivalent to a 2-degree grid at the equator. The updating method yields
probable errors of ± 4 minutes in D and ± 20 -y in H and Z over an 18-year reduction period. An estimate was
made of the chart residuals by making a random comparison of some 1,200 updated observations in D, H, Z with corresponding chart values. The following r.m.s. differences werc obtained: ±0.6 degree in D; ±125 -y in H, Z.
Computer hardware and programming requirements for the delay-sum-and-correlate method of processing seismic array data
Authors: Weichert D H
Published: March 2017

The data from the Yellowknife seismic array have been processed digitally in Ottawa since early 1966. The method used was the sum-delay-and-correlate method and required approximately 16, 000 words of computer memory when conducted at twice real-time speed,
because of trade-offs between memory and processing speed. For the particular configuration of the Yellowknife array, and for a sufficiently uniform crust, it is demonstrated that, with an average third generation computer with about 4 ?sec addition time and 24-bit word length, the data could be
processed continuously at four tilnes the recording speed. About 100 beams would be maintained, covering uniformly the third zone. The routine formation of digital files for all detected events is not possible at four times the recording speed, unless more than one direct-memory-access channel is
incorporated in the digital computer system. With two such channels, approximately one digital tape would be required per recording week. With only one channel as presently approved for purchase, digital tape formation for international data exchange is possible, but at twice real-time speed the
tape utilization is only 18%.
Seismic activity in the Canadian Arctic, 1899-1955
Authors: Meidler S S
Published: March 2017

From a search of available sources a list has been compiled of earthquakes which occurred in Canada or whose epicentres were so close to the Canadian border that they must have been felt in Canada. A total of 77 earthquakes are listed, covering the period from
September, 1899, to December, 1955. They vary in intensity from very weak shocks to the Yakutat Bay earthquake of magnitude 8. 6. Where possible , a description is given for the major tremors.
Prompt world-wide geomagnetic effects of high altitude nuclear explosions
Authors: Caner B
Published: March 2017

A brief summary of observational data is presented, covering the disturbances recorded within seconds of high-altitude nuclear explosions, with particular emphasis on the "phase B" signal recorded at H + 2 seconds following the "Starfish" test of July 9th, 1962.
The salient characteristics of this signal are specified: global synchronism at 2 seconds after the explosion ( ± 0.1 - 0.2 secs), large initial amplitudes (up to 30 - 50 Y) with an extremely sharp rise, initial frequency 0.25 - 0.28 cps, and altitude dependence, occurring only if the source is
above the E layer. Ten possible mechanisms are discussed and tested against the observational data. It is concluded that the only mechanisms which would satisfy all the observed characteristics are those involving hydromagnetic-electromagnetic conversions. Although no conclusive decision can be
reached on the basis of presently available data, the most likely one of these mechanisms appears to be hydromagnetic waves along the field line through the detonation point, with energy conversion into electromagnetic modes at the mirror points.
Determining mean hourly values
Authors: Darker W R
Published: March 2017

An electronic integrator with a tilne constant of one hour has been constructed for the purpose of deterrnining, in real time, the rnean hourly values of the magnetic field. After calibration, the error in output did not exceed S mv for an input voltage of 1
volt. Temperature drift, referred to the output, is 0.2 per cent/degree C. Used with a fluxgate magnetometer giving a signal of 10 mv/y, the integrator should
produce mean hourly values accurate to 1y.
Basic seismology and seismicity of Eastern Canada
Authors: Smith W E T
Published: March 2017

In 1928 seismographs capable of detecting the smaller shocks, within a radius of 200-300 miles, were installed in Canada along the St. Lawrence River. Since then, the seismic network has been expanded to more than 20 stations. By 1968 no part of Canada will be
more than about 300 miles from a sensitive seismograph. Seismograph records have accurate time scales making it possible to locate the source of an earthquake quite precisely. The instruments are carefully calibrated so that a measure of trace amplitude determines the earthquake's size on the
instrumental magnitude scale. A relationship between intensity and magnitude developed for the earthquakes of California has been found to hold reasonably well for Canadian earthquakes. This is of particular importance in the interpretation of the earthquake catalogues of eastern Canada and adjacent
areas. The catalogues are published as Vol. 26, No. 5 and Vol. 32, No. 3 of the Publications of the Dominion Observatory, Ottawa. The first contains the seismic history to the end of 192 7 and rates the shocks by maximum intensity. The second is an instrumental study of the earthquakes from 1928 to
1959 and rates the shocks by magnitude. Through the relationship of maximum intensity to magnitude a fairly consistent ranking, according to size, has been possible. Using the relationship of acceleration to intensity, the data can be used as the basis of more sophisticated seismicity
studies.
Mesozoic and Tertiary volcanism of the western Canadian Cordillera
Authors: Beaudoin A , Hall R J , Castilla G , Filiatrault M , Villemaire P , Skakun R , Guindon L
Published: March 2017

No Mesozoic or Tertiary rocks with the characteristics of oceanic crust are known in the Canadian Cordillera. The early Mesozoic was dominated by the successive formation and erosion of island arcs situated near the continent, whereas volcanism during the late
Mesozoic and Tertiary was entirely continental Spatial and temporal changes in the style of volcanism and the composition of lavas is believed to reflect changes in the interaction between Pacific crust and the continental margin.
An Astatic Magnetometer With Negative Feedback
Authors: He H , Xu H , Zhang Y , Gao K , Li H , Ma L , Li J
Published: March 2017

This paper describes an astatic magnetometer designed for the measurement of weakly magnetized rock specimens with special reference to a magnetic control method as a means of improving both the perfonnance and efficiency of the instrument. ln the first section,
it is shown that for high sensitivity and rapid response, the two magnets should be long and thin, magnetized perpendicular to the long axis, and that the moment of inertia of each magnet should be 1/4 the moment of inertia of the whole suspended system. ln general, magnetic materials of high
coercive force give the best design. The second section describes in detail the construction of an astatic magnetometer according to the above principles, including a method of astatizing without the use of trimmer magnets. Following a discussion on the size, shape and positioning of the rock
specimen, a cylindrical specimen (height/diameter =1T1 / 2/2) placed directly beneath the lower magnet is chosen. A specimen table and a method for accurate detennination of the distance between specimen and magnetometer are described. The third section describes the procedure for measuring three
orthogonal components of magnetization of a specimen. When the instrument is operated in the conventional manner, that is with the restoring torque provided by the suspension fibre, with a period of 14 seconds the sensitivity is 1 x 10-8 oe/mm deflection on a scale 5 m distant. This sensitivity
permits the measurement of specimens magnetized to an intensity of 1 x 10-6 e.m.u. The fourth section describes the use of negative feedback to improve the perfonnance and efficiency of the instrument. Here, in addition to the torque of the suspension, a magnetic restoring torque is provided by a
small solenoid connected to a pair of photo resistors centred on the light beam. Measurements can be made in tenns of current or voltage with a variety of electrical instruments. High sensitivity (0.56 x 10-9 oe/mv) can be obtained while maintaining a short period (5.1 sec). The sensitivity and the
period can be Iowered instantly through 11 steps down to 1.2 x 10-7 oe/mv and 1.2 sec. The quick response permits the direct measurement of the direction and total intensity of magnetization of the specimen, rather than computing them from three components. This eliminates much calculation and
increases the accuracy, especially with weakly magnetized rocks. The range of the instrument provides for accurate measurement of specimens magnetized to an intensity of 1 x 10-7 to 5 x 10-3 e.m.u.; the time required for a measurement of direction and intensity is eight and three minutes,
respectively, The period and damping of the system can be altered in many ways to suit particular conditions and requirements. Disturbances affecting the instrument and means of avoiding or reducing them are discussed.
Ottawa PZT observations 1956-1970, their comparison with BIH values by graphical, spectral and fourier analysis
Authors: Kim J -H , Yu J -S , Gaucher-loksts E , Roy B , Delisle V , Kim J -T
Published: March 2017

Results of measurements of latitude and time made with the Ottawa Photographie Zenith Tube (PZT) from 1956 to 1970 are given. The observations, on magnetic tape, are available to recognized scientific organizations at nominal cost. The observations are shown to
produce values of the variation in latitude and longitude with a probable error of 1'.0l. They were compared to the published results of the Rureau International de !'Heure. The residuals so formed were subjected to a spectral analysis and it is demonstrated that the PZT was not capable of detecting
secular motions of 10 cm or less. No motion was found for Ottawa. The star catalogue is published to contribute to the knowledge of stellar positions.
Un four électrique pour l'étude des propriétés magnétiques des roches
Authors: Gagnon B , Macdonald H , Hope E , Blair M
J , McKenney D W
Published: March 2017

The construction, characteristics, and performance of an electric oven (diameter 30.5 cm, height 20.3 cm) are described. The 'non-magnetic' materials used are discussed. The oven can accommodate 120 cylindrical samples (diameter 2.5 cm, height 2.2 cm) within a
magnetic field <6y 45 of which are within a field <1y. The magnetic field and the temperature are controlled automatically.
Investigations of gravity and isostacy in the southern Canadian Cordillera
Authors: Bassindale C , Wang X , Tyson W R , Xu S
Published: March 2017

A regional gravity investigation of southern British Columbia and southwestern Alberta is described. The values of gravity are obtained from a network of closed circuits, subjected to a least squares solution, while the instrumental calibration is made with
reference to stations established with the Cambridge pendulums. Maps of Bouguer and isostatic anomalies for the region are presented, and the compensation of the mountain systems is discussed. An Airy form of compensation appears reasonable, although certain features such as granitic batholiths show
considerable isostatic anomalies. Detailed measurements over the Rocky Mountain Trench indicate a considerable thickness of lighter fill in some sections, but do not strongly suggest a major crustal dislocation beneath it.
Investigations of gravitational and magnetometric methods of geophysical prospecting
Authors: Beaulieu J , Lenz P , Bousquet J
Published: March 2017

This report is a summary of investigations made with the torsion balance and the magnetometer by the Dominion Observatory. Surveys covered three faults, deposits of asbestos, chromite, pyrite, lignite, sidèrite, and sait, as well as a buried granite ridge
associa.ted with the occurrence of natural gas and oil at Monet.on, New Brunswick. Certain of the buried structures were successfuly located and outlined with the instruments. It is concluded that there are probably numerous other instances in Canada where the instruments might be successfully
and profitably employed.
Canadian west coast earthquakes, 1951
Authors: Yang Y , Piper D J W , Xu M , Gao J , Jia J , Normandeau A , Chu D , Zhou L , Wang Y P , Gao S
Published: March 2017

Three station triangulation of local earthquakes in the British Columbia Coast regions was initiated in August, 1951, making use of short period Benioff and Willmore seismographs. The three stations were located at Victoria and Alberni on Vancouver Island and at
Horseshoe Bay on the mainland. Seventy-four earthquakes were recorded in a five months' period and it was possible to determine epicentres for 27. Some indications were given of areas of localized activity but it is expected that at least another year's operation will be required before such areas
are at all clearly defined. Tables of epicentres and times are given and the stations and equipment are described.
A seismic survey in the Canadian Shield, I: refraction studies based on rockbursts at Kirkland Lake, Ontario
Authors: Hodgson J H
Published: March 2017

Between 1938 and 1943 a number of large rockbursts at Kirkland Lake were recorded at permanent seismological observatories in eastern Canada and New England. Analysis of these records suggested that rockbursts enjoy certain unique advantages as an energy source
in crustal studies, since they are susceptible of precise location and timing and yet have about the same energy distribution as earthquakes. Immediately after the war steps were taken lo set out a refraction profile for detailed studies of the crust.
A seismograph was installed at Kirkland Lake to time the bursts at their source and 14 stations were occupied at distances varying from 8 to 174 km. The locations were occupied one or two at a lime, the instruments being moved to new locations after bursts had been satisfactorily recorded. The
stations were housed in portable prefabricated buildings especially designed for the purpose.
Several types of instruments were used during the life of the project, those finally selected being of a type designed by Willmore for use in South African crustal studies. Particular attention was given to accurate timing and it is shown that the elapsed time of a single event has an accuracy of
the order of ± 0.06 seconds (p.e.).
The refraction profile obtained consists of the 14 field stations already mentioned plus 5 distant stations which recorded the earlier large bursts. First arrivals in the P and S groups suggest that the crust is single layered, and the point at which P is first observed provides confirmation of this
conclusion. In the analysis of secondary arrivals it becomes necessary to conclude that the crust, by lateral variation in rock types and by variable thickness, provides several alternate paths for each ray, so that groups of phases are obtained rather than single distinct phases. Within these
limits it is possible to account qualitatively for the secondary arrivals and lo conclude that reflections are obtained from the base of the crust as the critical angle is approached and exceeded.
The records of the distant stations show a very large amplitude for about 10 sec. following the expected arrival time of the direct S waves. This group appears to be identical with that called Lg by Ewing and Press.
P and S velocities in the crustal layer are 6.246 ± 0.015 and 3.544 ± 0.023 km/ sec., the uncertainties being probable errors. The P velocity below the Mohorovicic discontinuity is 7.913 ± 0.125 km/ sec. if near-station data are used, and 8.176 ± 0.013 km/ sec. combining data of
near and distant stations. This suggests an increase of velocity with with depth. Sn velocity, based on the records of the distant stations only, is 4.85 ± 0.10 km/ sec. The mean thickness of the crust, based on the P waves, is 35.4 ± 5.5 km., the uncertainty being the result of the
uncertainties in the velocities, and not a true probable error. It is suggested that this uncertainty corresponds to the actual variation in crustal thickness.
Gravity measurements in the Maritime Provinces
Authors: Zaeem M , Nadeem M , Pham T H , Ashiq W , Ali W , Gillani S S M , Moise E R
D , Leier H , Kavanagh V , Galagedara L , Cheema M , Thomas R
Published: March 2017

The results of all regional gravity measurements made by the Dominion Observatory in Nova Scotia, New Brunswick and Prince Edward Island are given, and the correlation of the Bouguer anomalies with major geological structures is discussed. It is shown that most
of the anomalies may be related to the densities of known formations. In several cases, the depth extents of these formations are estimated from their gravitational effects. A rather detailed interpretation is made of the structure of the Carboniferous basin in the region of Moncton, New
Brunswick.
Gravity and magnetic investigations along the Alaska Highway
Authors: Guo W -Y , Serra-Diaz J M , Schrodt F , Eiserhardt W L , Maitner B
S , Merow C , Violle C , Anand M , Belluau M , Bruun H H , Byun C , Catford J A , Cerabolini B E
L , Chacon-Madrigal E , Ciccarelli D , Hans, C C , Cornelissen, J , Dang-Le A T , de Frutos, A , Dias A
S , Giroldo A B , Guo K , Gutierrez A G , Hattingh W , He T , Hietz P , Hough-Snee N , Jansen S , Kattge J , Klein T , Komac B , Kraft N J B , Kramer K , Lavorel S , Lusk C
H , Martin A R , Mencuccini M , Michaletz S T , Minden V , Mori A S , Niinemets U , Onoda Y , Peñuelas J , Pillar V D , Pisek J , Robroek B J M , Schamp B , Slot M , Sosinski Ê
E , Soudzilovskaia N A , Thiffault N , van Bodegom, P , van, der der, Plas,
F , Wright I J , Xu W
-B , Zheng J , Enquist B J , Svenning J -C
Published: March 2017

A gravity and magnetic survey was made along the Alaska Highway between Dawson Creek, Alberta, and Fairbanks, Alaska, and 296 gravimeter stations were occupied. Ties were made to 10 pendulum stations covering a gravity range of 1486 mgls., and a calibration
factor of 0.246804 mg!., per scale division was derived for the gravimeters. A study of profiles of elevation, Bouguer anomaly, magnetic intensity and lithology leads to the following general interpretation. A 60-mgl. negative anomaly a.cross the Rocky Mountains has been attributed to a 16,000-foot
crustal downwarp, while an anomaly of similar magnitude but with steeper gradients across the Cassiar Mountains is considered to be due to a mass of low-density granite occurring within the mountain system.
A seismic survey in the vicinity of Vancouver Island, British Columbia
Authors: Elhefnawy M , Ouali M -S , Ragab A
Published: March 2017

ln cooperation with the Royal Canadian Navy and the Pacifie Naval Laboratory, a eeriee of precisely timed depth chargea were detonated in eelected areas adjacent to Vancouver Island, British Columbia. From the seismic travel-time curves considerable information
was obtained about crustal layera in this region. A granitic rock with a velocity of 6.3 km/eec apparently forme the basement rock for the area. South of Victoria this is covered by a volcanic rock with veloc!ty 5.4 km/sec, and it was possible to obtain measurements of depthe, and of the dip of the
bottom interface of this bed. Under the Strait of Georgia travel-time curves indicated a coneiderable thicknees of low-velocity material. Near the site of the Ripple Rock explosion another, lower velocity, volcanic rock reste on the granitic basement. Surface velocities have been measured in all
these areas ueing portable refraction equipment.
The gravity anomaly field in the Ungava region of northern Quebec
Authors: Huang X , Ng K W , Giroux L
Published: March 2017

During the summer seasons of 1959 and 1960, field parties of the Dominion Observatory made 614 regional gravity measurements in the Cape Smith-Wakeham Bay area of New Quebec. The Bouguer anomalies indicate that the area as a whole is in a state of isostatic
equilibrium. A linear Bouguer anomaly correlates with the basic volcanic and intrusive rocks of the Cape Smith belt. Calculations based on observed anomalies indicate that the folded basic rocks of the belt are thicker than 20,000 feet. Negative anomalies that flank the Cape Smith positive anomaly
can be explained isostatically by regarding the Cape Smith belt as a load on the crust. The thickness of the root, about 10,000 feet, calculated from the load itself agrees with that computed from the negative anomalies. A local positive anomaly in the Payne Bay area indicates the presence of a
large intrusive body. The presence of a gabbroic intrusion at the surface is confirmed by rock samples. Computations based on a residual Bouguer anomaly profile across the feature suggest that the body extends to a depth of about 40,000 feet is approximately 20 miles in diameter and has a central
dome a few thousand feet wide extending upward from the main body to the surface.
Gravity measurements in British Columbia
Authors: Buss J , Mansuy N , Laganière J , Persson D
Published: March 2017

Gravity Map No. 88 covers the coastarea of British Columbia andincludes the continental shelf, Vancouver Island, the Queen Charlotte Islands and the fiords of the mainland. The Bouguer anomalies have been contoured at 10 mgal irl.tervals and are based on gravity
measurements every 12 to 15 km. The terrain corrections have been computed using either a rectangular or a circular graticule or a combination of both depending on the scale of the available topographie maps. The major features of the gravity field are: a positive Bouguer anomaly along the western
edge of the area, which is associated with the change from continental to oceanic crust, and a negative anomaly along the Coast Mountains which is attributed to the thickening of the continental crust below the se mountains. Over the eastern part of the Queen Charlotte Islands, Hecate Strait, Queen
Charlotte Sound and Vancouver Island, changes in the Bouguer anomaly values have been related to density variations in the surface rocks.
The gravity field in the Richmond Gulf-fort Chimo area, Quebec
Authors: Wu Y , Wang H , Li H , Han X , Zhang M , Sun Y , Fan X , Tu R , Zeng Y , Xu C
C , Xu X
Published: March 2017

During the years 1959, 1960, 1961 and 1965 the Dominion Observatory observed some 1500 stations in northern Quebec west of 68°W and between latitudes 56°N and 60°N. Analysis of these measurements, together with observations taken in adjacent
regions of northern Quebec, suggests that the Bouguer anomalies have a relative accuracy of +/-2 mgal. Comparison of the Bouguer anomaly field with geology suggests that: (a) local and regional variations of Bouguer anomaly within the Superior Province can be correlated with occurrences of
high-grade metamorphic rocks (granulites) , and (b) the linear negative anomaly over the Labrador Trough is most likely caused by deepseated structure.