The Chelmsford-Lowell, Massachusetts, earthquake of 23 November 1980: Depth control and fault plane solution

1981 ◽  
Vol 71 (4) ◽  
pp. 1369-1372
Author(s):  
Jay J. Pulli ◽  
Michael J. Guenette
Keyword(s):  
New England ◽  
Fault Plane ◽  
Seismic Station ◽  
Focal Depth ◽  
Strike Slip ◽  
Fault Plane Solution ◽  
Origin Time ◽  
Small Magnitude ◽  
Depth Control ◽  
Plane Solution

abstract On 23 November 1980, a small (magnitude 2.9) earthquake occurred on the Chelmsford-Lowell, Massachusetts, border, approximately 10 km northeast of the MIT seismic station at Westford, Massachusetts (WFM). Thus we were able to accurately determine the focal depth, which is generally not the case in New England. Our hypocentral solution was latitude 41.63, longitude −71.36, depth 1.5 km, at origin time 00:39:32.0 UTC. The fault plane solution shows either strike-slip or dip-slip faulting with a P axis trending NE-SW, which is in agreement with overcoring measurements in a nearby granite quarry.

scholarly journals Main shock and aftershocks of the December 13, 1990, Eastern Sicily earthquake

1995 ◽  
Vol 38 (2) ◽  
Author(s):  
A. Amato ◽  
R. Azzara ◽  
A. Basili ◽  
C. Chiarabba ◽  
M. Cocco ◽  
...  
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
Source Parameters ◽  
Source Region ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Local Network ◽  
Fault Plane Solution ◽  
Slip Mechanism ◽  
Plane Solution

n this paper we describe the location and the fault plane solution of the December 13, 1990, Eastern Sicily earthquake (ML = 5.4), and of its aftershock sequence. Because the main shock location is not well constrained due to the geometry of the permanent National Seismic Network in this area, we used a "master event" algorithm to locate it in relation to a well located aftershock. The revised location is slightly offshore Eastern Sicily, 4.8 km north of the largest aftershock (ML = 4.6) that occurred on December 16, 1990. The main shock has a strike-slip mechanism, indicating SE-NW compression with either left lateral motion on a NS plane, or right lateral on an EW plane. Two days after the main event we deployed a local network of eight digital stations, that provided accurate locations of the aftershocks, and the estimate of source parameters for the strongest earthquake. We observed an unusual quiescence after the ML = 5.4 event, that lasted until December 16, when a ML = 4.6 earthquake occurred. The fault plane solution of this aftershock shows normal faulting on E-W trending planes. Between December 16 and January 6, 1991, a sequence of at least 300 aftershock" was recorded by the local network. The well located earthquakes define a small source region of approximately 5 x 2 x 5 km3, with hypocentral depths ranging between 15 and 20 km. The paucity of large aftershocks, the time gap between the main shock occurrence and the beginning of the aftershock sequence (3.5 days), their different focal mechanisms (strike-slip vs. normal), and the different stress drop between main shock and after- shock suggest that the ML = 5.4 earthquake is an isolated event. The sequence of aftershocks began with the ML = 4.6 event, which is probably linked to the main shock with a complex mechanism of stress redistribution after the main faulting episode.

The San Salvador Earthquake of October 10, 1986—Seismological Aspects and Other Recent Local Seismicity

1987 ◽  
Vol 3 (3) ◽  
pp. 419-434 ◽  
Author(s):  
Randall A. White ◽  
David H. Harlow ◽  
Salvador Alvarez
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
Vertical Plane ◽  
Aftershock Sequence ◽  
Central American ◽  
Fault Plane Solution ◽  
San Salvador ◽  
The North ◽  
Volcanic Chain ◽  
Plane Solution

The San Salvador earthquake of October 10, 1986 originated along the Central American volcanic chain within the upper crust of the Caribbean Plate. Results from a local seismograph network show a tectonic style main shock-aftershock sequence, with a magnitude, Mw, 5.6. The hypocenter was located 7.3 km below the south edge of San Salvador. The main shock ruptured along a nearly vertical plane toward the north-northeast. A main shock fault-plane solution shows a nearly vertical fault plane striking N32\sz\E, with left-lateral sense of motion. This earthquake is the second Central American volcanic chain earthquake documented with left-lateral slip on a fault perpendicular to the volcanic chain. During the 2 1/2 years preceeding the earthquake, minor microseismicity was noted near the epicenter, but we show that this has been common along the volcanic chain since at least 1953. San Salvador was previously damaged by a volcanic chain earthquake on May 3, 1965. The locations of six foreshocks preceding the 1965 shock show a distinctly WNW-trending distribution. This observation, together with the distribution of damage and a fault-plane solution, suggest that right-lateral slip occurred along a fault sub-parallel with Central American volcanic chain. We believe this is the first time such motion has been documented along the volcanic chain. This earthquake was also unusual in that it was preceded by a foreshock sequence more energetic than the aftershock sequence. Earlier this century, on June 08, 1917, an Ms 6.4 earthquake occurred 30 to 40 km west of San Salvador Volcano. Only 30 minutes later, an Ms 6.3 earthquake occurred, centered at the volcano, and about 35 minutes later the volcano erupted. In 1919 an Ms 6 earthquake occurred, centered at about the epicenter of the 1986 earthquake. We conclude that the volcanic chain is seismically very active with variable styles of seismicity.

A study of the Koyna earthquake of December 10, 1967

1969 ◽  
Vol 59 (3) ◽  
pp. 1149-1162
Author(s):  
Harsh Gupta ◽  
Hari Narain ◽  
B. K. Rastogi ◽  
Indra Mohan
Keyword(s):  
Fault Plane ◽  
Time Lag ◽  
India Meteorological Department ◽  
Activity Level ◽  
Research Station ◽  
Fault Plane Solution ◽  
Plane Solution ◽  
Maximum Expected Magnitude ◽  
Different Origin

abstract Data now available on the Koyna earthquake have been studied in detail. Different origin times and epicenters given by India Meteorological Department and Central Water and Power Research Station, field evidences and nature of the seismograms for this earthquake suggest a multiple event. A fault plane solution has been obtained by using the sense of first motions. Seismicity in Koyna region has been found to increase with the increase of water level in the reservoir and vice-versa with a certain time lag. The two major earthquakes of this region have similar foreshock-aftershock pattern, corresponding to type 2 of Mogi's (1963) models. Aftershocks of this earthquake are related by a function Log N = a + bM, value of b being −0.8. Possibility of predicting maximum expected magnitude at a certain seismic activity level of Koyna region has been also pointed out.

Surface fault traces, fault plane solution and spatial distribution of the aftershocks of the September 13, 1986 earthquake of Kalamata (Southern Greece)

1988 ◽  
Vol 126 (1) ◽  
pp. 55-68 ◽  
Author(s):  
B. Papazachos ◽  
A. Kiratzi ◽  
B. Karacostas ◽  
D. Panagiotopoulos ◽  
E. Scordilis ◽  
...  
Keyword(s):  
Spatial Distribution ◽  
Fault Plane ◽  
Fault Plane Solution ◽  
Plane Solution ◽  
Southern Greece

scholarly journals Fault-Plane Solution of the Earthquake of 19 March 2005 in Monatele (Cameroon)

2014 ◽  
Vol 04 (06) ◽  
pp. 289-293 ◽  
Author(s):  
Eric N. Ndikum ◽  
Charles T. Tabod ◽  
Alain-Pierre K. Tokam ◽  
Bernard Z. Essimbi
Keyword(s):  
Fault Plane ◽  
Fault Plane Solution ◽  
Plane Solution
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