HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) References Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by SMITH, T. E. T. Articles by PICHÉ, W. T. Search for Related Content GeoRef GeoRef Citation

A microearthquake swarm in 1965 near Mould Bay, N.W.T., Canada

DIVISION OF SEISMOLOGY, OBSERVATORIES BRANCH DEPARTMENT OF ENERGY, MINES AND RESOURCES, OTTAWA 3 ONTARIO, Canada

Abstract

In a 30-day period beginning March 29, 1965, some 2026 microearthquakes were recorded at MBC and by the array NPNT. About 10 per cent of them were located. The extent of the epicentral region was 3 sq km and of the hypocentral region 8 cu km. The centroid of the hypocenters was 12.6 km from MBC on an azimuth of 121° and at a depth of 6.8 km, very nearly on the strike of an old fault. Although no foreshock-aftershock series could be distinguished, the events were not independent nor randomly distributed in time.

Particle motion diagrams were drawn for 10 events. These identified the longitudinal and transverse waves and confirmed the azimuths and angles of emergence obtained from amplitude data. The array data also confirmed the azimuths and yielded a P-wave velocity of 4.33 km/s near the surface.

The magnitudes ranged from – 1.1 to 2.9 and the frequency-magnitude relation was:

The coefficient 0.68 suggests tectonic activity. The partition of energy between P and S, and the observed directions of motion (all compressions at MBC) are compatible with the double couple model of focal mechanism and motion on the old fault. However, magma movement cannot be entirely ruled out as there exists geomagnetic evidence of abnormally high upper mantle temperatures.

The following energy-magnitude relation was determined from 100 events in the range 0.1 M_L 1.6:

This article has been cited by other articles:

				H. Bungum, O. Olesen, C. Pascal, S. Gibbons, C. Lindholm, and O. VestOl To what extent is the present seismicity of Norway driven by post-glacial rebound? Journal of the Geological Society, March 1, 2010; 167(2): 373 - 384. [Abstract] [Full Text] [PDF]

				R. J. WETMILLER An earthquake swarm on the Queen Charlotte Islands Fracture Zone Bulletin of the Seismological Society of America, December 1, 1971; 61(6): 1489 - 1505. [Abstract] [PDF]

				J. F. EVERNDEN Study of regional seismicity and associated problems Bulletin of the Seismological Society of America, April 1, 1970; 60(2): 393 - 446. [Abstract] [PDF]