Cliff collapse and rock avalanches (sturzstroms) in the Mackenzie Mountains, northwestern Canada

1979 ◽  
Vol 16 (2) ◽  
pp. 309-334 ◽  
Author(s):  
G. H. Eisbacher
Keyword(s):  
Roller Bearing ◽  
Maximum Level ◽  
Static Friction ◽  
Bedding Plane ◽  
Mechanical Analysis ◽  
Fault Scarp ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Rock Avalanches ◽  
Mackenzie Mountains

Cliff collapse and resulting rock avalanches or sturzstroms have occurred widely in carbonate formations of the Mackenzie Mountains, northwestern Canada. Some of the rock slides are close to a Holocene fault scarp and may be due to past earthquake activity. The Mackenzies are located within an intraplate seismic zone; presently monitored seismic activity may not indicate the maximum level of ground motion that caused failure of large rock slopes during the last 10 000 years. At several localities at least two generations of slide material can be recognized. All major sturzstroms originated by failure above inclined bedding plane surfaces, ranging in dip from 13–40°.The mechanical analysis of dry sturzstroms has to consider two stages: failure and streaming. Failure can occur by either 'sliding' (static friction of about tan 30°) or 'roller bearing' and internal collapse (kinetic friction as low as tan 13°). Streaming is initiated by momentum transfer from the back of a collapsing cliff to its frontal disintegrating portion and facilitated by dispersion of large blocks in finer interstitial material. Prediction of reach or excessive travel distance of dry sturzstroms is not a simple matter and one has to consider the effect of slide mass, fall height, topographic constraints, and lithology. The best method of predicting reach in a potential sturzstrom situation is comparison with documented sturzstroms in similar geologic, climatic, and topographic settings.

A reassessment of transport mechanisms of some rock avalanches in the Mackenzie Mountains, Yukon and Northwest Territories, Canada

1990 ◽  
Vol 27 (1) ◽  
pp. 129-144 ◽  
Author(s):  
P. K. Kaiser ◽  
J. V. Simmons
Keyword(s):  
Debris Flow ◽  
Northwest Territories ◽  
Valley Bottom ◽  
Flow Simulations ◽  
Rock Avalanches ◽  
Field Evidence ◽  
Debris Transport ◽  
Glacier Ice ◽  
Mackenzie Mountains ◽  
New Hypothesis

The transport mechanism of some rock avalanches of the Mackenzie Mountains in the Yukon and Northwest Territories of Canada is reassessed on the basis of evidence collected during fieldwork and by comparison with results from numerical simulations of the debris flow mechanism. A new hypothesis of glaciation-related transport is advanced as an alternate explanation of apparently very mobile rock avalanches with anomalous travel distances. By the example of the Avalanche Lake slide, it is demonstrated that the debris was most likely not deposited on the current topography but on valley glacier ice at an elevation of about 400–500 m above the valley bottom. This conclusion is supported by field evidence, an empirical runup relationship, and the results from numerical flow simulations. A qualitative interpretation of other debris deposits suggests that several events in the Mackenzie Mountains can be interpreted in the same manner. Key words: rock avalanches, rock slides, debris transport, debris flow modelling, Mackenzie Mountains, Northwest Territories.

Wavelet analysis of the temporal-spatial distribution in the Eurasia seismic belt

2017 ◽  
Vol 15 (03) ◽  
pp. 1750018 ◽  
Author(s):  
Wenfeng Zheng ◽  
Xiaolu Li ◽  
Lirong Yin ◽  
Zhengtong Yin ◽  
Bo Yang ◽  
...  
Keyword(s):  
Fault Zone ◽  
Compact Support ◽  
Large Scale ◽  
Temporal Distribution ◽  
Seismic Energy ◽  
Research Area ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Seismic Belt ◽  
Earthquake Fault

Due to the growing frequency of earthquakes, safeties of human lives and properties are facing serious threats. However, the research in the field of spatial-temporal distribution of earthquake is quite a few. In this paper, we use wavelet model to analyze the spatial-temporal distribution of earthquakes. Because the spatial-temporal distribution of earthquake activity is closely related to the distribution of the earthquake fault zone, we analyze large-scale earthquake clusters by selecting the Eurasia seismic belt and the surrounding region as the research area. From the perspective of the time domain, the results show that the seismic energy of the earthquake fault zone presences compact support or similar compact support distribution, suggesting that the seismic zone exists a relatively quiet period and active stage. This indicate that the seismic zone is periodical. The period of strong earthquakes above normal and less than normal is different by time changes. The cycles of earthquakes are different due to different regions and different geological and geographical environment.

Seismic Reflection Expression of Reactivated Structures in the New Madrid Rift Complex

1988 ◽  
Vol 59 (4) ◽  
pp. 141-150 ◽  
Author(s):  
John. L. Sexton
Keyword(s):  
Seismic Reflection ◽  
Structural Features ◽  
Normal Faults ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Reflection Method ◽  
Intraplate Earthquakes ◽  
Reflection Data ◽  
Seismic Reflection Method ◽  
New Madrid

Abstract An important aspect of seismogenesis concerns the role of preexisting faults and other structural features as preferred zones of weakness in determining the pattern of strain accumulation and seismicity. Reactivation of zones of weakness by present day stress fields may be the cause of many intraplate earthquakes. To understand the relation between reactivated structures and seismicity, it is necessary to identify structures which are properly oriented with respect to the present-day stress field so that reactivation can occur. The seismic reflection method is very useful for identifying and delineating structures, particularly in areas where the structures are buried as in the New Madrid seismic zone. Application of the seismic reflection method in widely separated locations within the New Madrid rift complex has resulted in successful detection and delineation of reactivated rift-related structures which are believed to be associated with earthquake activity. The purpose of this paper is to discuss results from seismic reflection profiling in the New Madrid rift complex. Reflection data from several surveys including USGS Vibroseis* surveys in the Reelfoot rift area reveal reactivated faults and other deep rift-related structures which appear to be associated with seismicity. High-resolution explosive and Mini-Sosie** reflection surveys on Reelfoot scarp and through the town of Cottonwood Grove, Tennessee, clearly show reverse faults in Paleozoic and younger rocks which have been reactivated to offset younger rocks. A Vibroseis survey in the Wabash Valley area of the New Madrid rift complex provides direct evidence for a few hundred feet of post-Pennsylvanian age reactivation of large-offset normal faults in Precambrian-age basement rocks. Several earthquake epicenters have been located in the vicinity of these structures. In the Rough Creek graben, Vibroseis reflection data provide clear evidence for reactivation of basement faults. The success of these reflection surveys shows that well-planned seismic reflection surveys must be included in any program seeking to determine the relationship between preexisting zones of weakness and seismicity of an area.

Natural Seismicity in and around the Rome Trough, Eastern Kentucky, from a Temporary Seismic Network

2020 ◽  
Vol 91 (3) ◽  
pp. 1831-1845 ◽  
Author(s):  
N. Seth Carpenter ◽  
Andrew S. Holcomb ◽  
Edward W. Woolery ◽  
Zhenming Wang ◽  
John B. Hickman ◽  
...  
Keyword(s):  
New York ◽  
Oil And Gas ◽  
Seismic Network ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Injection Wells ◽  
Eastern Kentucky ◽  
The North ◽  
Horizontal Compressive Stress ◽  
Natural Seismicity

Abstract The Rome trough is a northeast-trending graben system extending from eastern Kentucky northeastward across West Virginia and Pennsylvania into southern New York. The oil and gas potential of a formation deep in the trough, the Rogersville shale, which is ∼1  km above Precambrian basement, is being tested in eastern Kentucky. Because induced seismicity can occur from fracking formations in close proximity to basement, a temporary seismic network was deployed along the trend of the Rome trough from June 2015 through May 2019 to characterize natural seismicity. Using empirical noise models and theoretical Brune sources, minimum detectable magnitudes, Mmin, were estimated in the study area. The temporary stations reduced Mmin by an estimated 0.3–0.8 magnitude units in the vicinity of wastewater-injection wells and deep oil and gas wells testing the Rogersville shale. The first 3 yr of seismicity detected and located in the study area has been compiled. Consistent with the long-term seismicity patterns in the Advanced National Seismic System Comprehensive Catalog, very few earthquakes occurred in the crust beneath the Rome trough—only three events were recorded—where the temporary network was most sensitive. None of these events appear to have been associated with Rogersville shale oil and gas test wells. Outside of the trough boundary faults, earthquakes are diffusely distributed in zones extending into southern Ohio to the north, and into the eastern Tennessee seismic zone to the south. The orientations of P axes from the seven first-motion focal mechanisms determined in this study are nearly parallel with both the trend of the Rome trough and with the orientation of maximum horizontal compressive stress in the region. This apparent alignment between the regional stress field and the strikes of faults in the trough at seismogenic depths may explain the relative lack of earthquake activity in the trough compared with the surrounding crust to the north and south.

Seismic activity and structural features in the Charlevoix region, Quebec

1987 ◽  
Vol 24 (11) ◽  
pp. 2118-2129 ◽  
Author(s):  
Maurice Lamontagne
Keyword(s):  
Seismic Activity ◽  
Impact Crater ◽  
Time Window ◽  
Fault System ◽  
Earthquake Risk ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Nodal Solutions ◽  
Data Set ◽  
The Impact

The Charlevoix region is historically the most active earthquake zone in eastern Canada. Understanding the links between its seismicity and the faults of the region is important for the assessment of earthquake risk along the St. Lawrence Valley. The region has been monitored by a microseismic array since 1977, yielding accurate locations of the hypocentres. Previous analyses of data from the array indicated a relationship between the earthquakes and the St. Lawrence Valley paleorift faults. As a sequel to previous studies, the relationships between the seismic activity and the faults of the region were reexamined through the use of the composite P-nodal solutions, in an effort to clarify the nature of faulting in the seismic zone. The microseisms were partitioned into subsets of events on the basis of geological and hypocentre-trend considerations. The main objectives of this paper are to delineate the details of faulting within the Charlevoix region and to determine the effect of the impact crater on the nature of faulting in this area.Assuming a constant 6.2 km/s velocity model and using a data set of 107 events, composite fault-plane solutions were computed. The composite P-nodal solutions indicated that the Charlevoix impact crater modifies to a certain extent the focal-mechanism characteristics. Events outside the impact crater were found to be quite consistent in their polarity distribution on the focal sphere, suggesting similarity in their focal mechanisms. The composite mechanism of these events suggests a relationship between the earthquakes and the north–south faults mapped outside the impact crater. The magnitude mb (Lg) 5.0 earthquake of August 19, 1979, the largest event in the selected time window, had different fault planes than some of its aftershocks. Nevertheless, the polarity distribution of the aftershocks was in agreement with the average trend for the events outside the crater. Events inside the impact crater were found to be produced along more variable fault orientations, with an average trend similar to that of the rift fault system. It is proposed that the meteor impact weakened the rift faults and introduced its own fractures. The present earthquake activity probably occurs along these weak fault surfaces. The effect of the impact crater on the type of faulting versus depth is not readily discernible from available data. In general, meteor impacts do not leave neotectonic seismic signatures: the Charlevoix impact crater might represent a different case because of the presence of weakened paleorift faults.

scholarly journals Conservation of historic buildings in
 a seismic zone

1988 ◽  
Vol 21 (2) ◽  
pp. 128-134
Author(s):  
Ian Bowman
Keyword(s):  
New Zealand ◽  
Earthquake Activity ◽  
Historic Buildings ◽  
Seismic Zone

Following the accepted principles and practice of conservation of historic buildings in New Zealand is complicated by the proximity to earthquake activity. The author's own research, outlined in this article, draws some conclusions.

Hunting for Quaternary Faults in Eastern Canada: A Critical Appraisal of Two Potential Candidates

2020 ◽  
Author(s):  
Nicolas Pinet ◽  
Maurice Lamontagne ◽  
Mathieu J. Duchesne ◽  
Virginia I. Brake
Keyword(s):  
River Estuary ◽  
Seismic Profile ◽  
Fault Scarp ◽  
Seismic Zone ◽  
Eastern Canada ◽  
Lawrence Estuary ◽  
Surface Ruptures ◽  
St Lawrence Estuary ◽  
Fault Scarps ◽  
St Lawrence River

Abstract This study documents two potential neotectonic features in the seismically active St. Lawrence estuary and western part of the Gulf of St. Lawrence of Quebec, Canada. Historically, the region is the locus of series of damaging earthquakes, including the 1663 M 7 earthquake, which suggests the occurrence of coseismic surface ruptures beneath the St. Lawrence River. In the western Gulf of St. Lawrence (Lower St. Lawrence seismic zone), a potential fault scarp identified on a vintage seismic profile has been investigated through high-resolution seismic and multibeam bathymetry data. On the seafloor, the scarp corresponds to an ∼1.8  m high (maximum) feature that is located above a buried escarpment of the Paleozoic bedrock. Holocene units are draping over the escarpment on one profile, but are possibly cut on two others. The scarp meets several of the criteria generally associated with neotectonic features. However, a close look at the data indicates that the staircase geometry of the top of the bedrock and its expression at the surface is linked, at least partially, with the presence of an erosion-resistant unit. This makes a neotectonic reactivation possible but not proven. In the Tadoussac area, ∼40  km north of the Charlevoix seismic zone, the offshore extension of the St. Laurent fault corresponds to an ∼110  m high bathymetric escarpment with well-preserved triangular facets. Such “fresh” morphology is unique in the St. Lawrence River Estuary and may attest to Quaternary displacements, yet other interpretations may also explain the unusual preservation of the escarpment. These two case studies illustrate the difficulty to unambiguously document Holocene fault scarps, even in the marine domain in which the sedimentary succession is generally continuous.

The Utility of Geopotential Field Data in Seismotectonic Studies in the Eastern United States

1988 ◽  
Vol 59 (4) ◽  
pp. 289-297 ◽  
Author(s):  
William J. Hinze ◽  
Thomas G. Hildenbrand
Keyword(s):  
United States ◽  
Magnetic Anomaly ◽  
Spatial Relationship ◽  
Gravity Anomalies ◽  
Three Dimensions ◽  
Hazard Evaluation ◽  
Earthquake Activity ◽  
Seismic Zone ◽  
Eastern United States ◽  
Isostatic Gravity

Abstract The deterministic approach to seismic hazard evaluation utilizes all available geologic/geophysical information to map the structure and nature of the crust in three dimensions that may relate to earthquake activity. However, information on the crystalline crust of the eastern United States from direct observations, drilling and sparse crustal seismic studies is limited. In contrast, regional gravity and magnetic anomaly data exist over the entire eastern United States and are available in a digital grid to facilitate processing and analysis. Although these data have serious limitations for detailed interpretation, they can be used to estimate the strength of the crust and the lithosphere and to map and characterize (1) zones of weakness such as paleorifts, sutures, and faults; (2) regions of potential stress amplifications such as plutons and irregularities in fault zones; and (3) basement terranes of generally consistent structural pattern that may delimit coherent regional seismic zones. Free-air, Bouguer, and isostatic gravity anomalies have different applications in the characterization of the crust for seismogenic purposes and complement magnetic anomaly maps which focus on upper crustal features. In concert, these data have provided the insight to interpret the host structures that together with related seismic and geoscience data, suggest causative mechanisms of the New Madrid seismic zone and other seismogenic regions of the eastern United States. As a result, we conclude that interpretations of geopotential anomalies are an essential ingredient in seismotectonic studies in the eastern United States, but they are only one of several tools required in the concerted effort of assessing seismic hazards. The presence of anomalies with a particular set of attributes neither confirms nor denies the possible spatial relationship to seismicity.

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