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EARTHQUAKe Records by the Milne SeismograPH
SIR FREDERIC STUPART, DIRECTOR.
Preliminary Tremors, S. = Secondary Waves. L.W. - Large Waves. A.C.
= Air Currents.
Micros when other station records small quake.
Micros, going on when other station records small quake.
Boom period 18 seconds. Pillar inclination Imm. o" 45.
Estevan reports two local tremors at 9 a. m. G.M.T. on the 11th not recorded
8 42 40 9 29 00: 490
12 04 24 12 16 00 71
RECORDS AT TORONTO AND VICTORIA, B.C., OF THE EARTHQUAKE OFF VANCOUVER ISLAND,
DECEMBER 6TH, 1918
Seismographs all over the continent were disturbed on December 6th by an earthquake of considerable intensity. It is of special interest since it occurred in a district heretofore more or less immune.
By employment of five stations and Dr. Klotz's stereographic projection method, the epicentre is found to be 49° 32′ N. and 127° west; 185 miles W NW of Victoria, 25 miles off Estevan Point.
The disturbance apparently travelled from a northwesterly to a southeasterly direction, as it was reported in Estevan at 12.40; Victoria, two minutes later; and in Vancouver and Seattle at 12.45. Toronto records an amplitude of 6 8 mm., whilst in Washington the shock was so great that the needles were dislodged from the instrument. Seismographs were not alone in recording the shock for it was felt by a very large section of the public. In Victoria, the tremor awakened sleepers, shook houses and otherwise left marks of its visit. Similar reports come from all over the district, particularly from the southern section of the city where residents experienced the oscillations in a more marked manner than on the high levels.
Press despatches give the following information:
"In Vancouver, many people were awakened by the tumbling of furniture and the dislocation of dishes, whilst the shock was particularly severe on the west coast of Vancouver Island, some sleepers being thrown out of bed.
"In Nanaimo, pictures fell from the walls; and in Seattle, buildings in the downtown district were shaken.
"The tremor seems to have been most marked at Estevan, that portion of the Island seaboard being in the line of weakness of the Cordilleras of the Pacific slope. Estevan Point lighthouse, one of the most powerful lights on the British Columbia
coast, has been temporarily put out of commission.
The quake shook the mercury out of the lens table so that the lens cannot revolve until new mercury has been supplied. The lens is of cut glass and brass weighing about a ton, the interior being so roomy as to allow a man to move about within, for the purpose of cleaning the glass. This immense lens floats on mercury contained in a huge bowl at the apex of the concrete tower, and is so perfectly balanced that it can be turned by the human fingers. The lens is revolved on the mercury by clockwork. 343 pounds of mercury are required to float it, so that the damage to the powerful light may easily be appreciated. The light is 125 feet above sea. The rays from the Estevan lamps are reflected 50 miles to seaward, the direct rays having a radius of about 25 miles. This light is one of the first to be picked up off the shore by vessels engaged in the trans-Pacific trade."
During the month of November the earth's magnetic field, according to the records obtained at Agincourt and Meanook was less disturbed than for some time. This condition synchronizes with lessened frequency of sunspots as observed at Toronto by Mr. Blake, and with fewer reports of aurora from meteorological observers in Canada.
Active magnetic disturbances of moderate intensity were recorded on the 11th, 12th, 13th, 23rd and 30th.
display of sunspots was from the 19th to the 23rd, and reports of aurora were most numerous on the nights of the 10th, 11th and 22nd.