scholarly journals Statistical analysis of recent fault-plane solutions of earthquakes

1959 ◽  
Vol 49 (4) ◽  
pp. 337-347
Author(s):  
A. E. Scheidegger
Keyword(s):  
Statistical Analysis ◽  
Fault Plane ◽  
Strike Slip ◽  
Slip Angle ◽  
Fault Plane Solutions ◽  
Deep Earthquakes ◽  
Central Asian ◽  
Normal Character ◽  
The Relationship

Abstract The large number of fault-plane solutions at present available in the literature permit one to calculate several statistical averages that have an important bearing upon geotectonics. The present paper represents a continuation of earlier work in this direction: 101 new fault-plane solutions are listed and the ratio of pressure to tension, strike slip to dip slip, and the average slip angle have been calculated for nine earthquake areas. Some of the older results are thereby corroborated, viz., that the “normal” character of earthquakes is to represent strike-slip faulting, and that the central Asian regions constitute an exception to this rule. In addition, it is now possible to make a breakdown with regard to depth. In this, a peculiar situation is found at 0.03 R depth, where the slip angle reaches a maximum. If the relationship between shallow and deep earthquakes be considered for any one area, however, it turns out that they are on the whole of the same character. Thus, whatever it is that causes earthquakes, acts in a similar fashion at all depths in any one area, but differs from one area to another.

Microearthquake seismicity and tectonics of Coastal Northern California

1970 ◽  
Vol 60 (5) ◽  
pp. 1669-1699 ◽  
Author(s):  
Leonardo Seeber ◽  
Muawia Barazangi ◽  
Ali Nowroozi
Keyword(s):  
High Frequency ◽  
Fault Plane ◽  
San Andreas Fault ◽  
High Gain ◽  
Strike Slip ◽  
Fault System ◽  
Northern California ◽  
Fault Plane Solutions ◽  
Sharp Bend ◽  
San Andreas

Abstract This paper demonstrates that high-gain, high-frequency portable seismographs operated for short intervals can provide unique data on the details of the current tectonic activity in a very small area. Five high-frequency, high-gain seismographs were operated at 25 sites along the coast of northern California during the summer of 1968. Eighty per cent of 160 microearthquakes located in the Cape Mendocino area occurred at depths between 15 and 35 km in a well-defined, horizontal seismic layer. These depths are significantly greater than those reported for other areas along the San Andreas fault system in California. Many of the earthquakes of the Cape Mendocino area occurred in sequences that have approximately the same magnitude versus length of faulting characteristics as other California earthquakes. Consistent first-motion directions are recorded from microearthquakes located within suitably chosen subdivisions of the active area. Composite fault plane solutions indicate that right-lateral movement prevails on strike-slip faults that radiate from Cape Mendocino northwest toward the Gorda basin. This is evidence that the Gorda basin is undergoing internal deformation. Inland, east of Cape Mendocino, a significant component of thrust faulting prevails for all the composite fault plane solutions. Thrusting is predominant in the fault plane solution of the June 26 1968 earthquake located along the Gorda escarpement. In general, the pattern of slip is consistent with a north-south crustal shortening. The Gorda escarpment, the Mattole River Valley, and the 1906 fault break northwest of Shelter Cove define a sharp bend that forms a possible connection between the Mendocino escarpment and the San Andreas fault. The distribution of hypocenters, relative travel times of P waves, and focal mechanisms strongly indicate that the above three features are surface expressions of an important structural boundary. The sharp bend in this boundary, which is concave toward the southwest, would tend to lock the dextral slip along the San Andreas fault and thus cause the regional north-south compression observed at Cape Mendocino. The above conclusions support the hypothesis that dextral strike-slip motion along the San Andreas fault is currently being taken up by slip along the Mendocino escarpment as well as by slip along northwest trending faults in the Gorda basin.

Rampart seismic zone of central Alaska

1983 ◽  
Vol 73 (3) ◽  
pp. 813-829
Author(s):  
P. Yi-Fa Huang ◽  
N. N. Biswas
Keyword(s):  
Main Shock ◽  
Fault Plane ◽  
B Value ◽  
Aftershock Sequence ◽  
Strike Slip ◽  
Lithospheric Plate ◽  
Normal Faults ◽  
Seismic Zone ◽  
The West ◽  
Fault Plane Solutions

abstract This paper describes the characteristics of the Rampart seismic zone by means of the aftershock sequence of the Rampart earthquake (ML = 6.8) which occurred in central Alaska on 29 October 1968. The magnitudes of the aftershocks ranged from about 1.6 to 4.4 which yielded a b value of 0.96 ± 0.09. The locations of the aftershocks outline a NNE-SSW trending aftershock zone about 50 km long which coincides with the offset of the Kaltag fault from the Victoria Creek fault. The rupture zone dips steeply (≈80°) to the west and extends from the surface to a depth of about 10 km. Fault plane solutions for a group of selected aftershocks, which occurred over a period of 22 days after the main shock, show simultaneous occurrences of strike-slip and normal faults. A comparison of the trends in seismicity between the neighboring areas shows that the Rampart seismic zone lies outside the area of underthrusting of the lithospheric plate in southcentral and central Alaska. The seismic zone outlined by the aftershock sequence appears to represent the formation of an intraplate fracture caused by regional northwest compression.

scholarly journals SCALE-FREE NETWORK THEORY IN STUDYING THE STRUCTURE OF THE ROAD NETWORK IN POLAND

2014 ◽  
Vol 26 (3) ◽  
pp. 235-242 ◽  
Author(s):  
Katarzyna KOCUR-BERA
Keyword(s):  
Statistical Analysis ◽  
Traffic Flow ◽  
Network Theory ◽  
Road Network ◽  
Scale Free Network ◽  
Scale Free ◽  
The Road ◽  
Normal Character ◽  
Free Network ◽  
The Relationship

This paper discusses the issue of statistical analysis of traffic flow in different regions of Poland. Such analysis allows us to identify “valuable (sensitive) areas” whose damage or blockage may provoke considerable disturbances or even a stoppage of traffic flow in the examined road network. The results of the studies indicate that the road network in Poland has the properties of a scale-free network. The distribution of the examined variables does not have a normal character, whereas the relationship between the number of nodes and the number of connections is a power-law feature. 

Aftershocks of the Benham nuclear explosion

1969 ◽  
Vol 59 (6) ◽  
pp. 2271-2281
Author(s):  
R. M. Hamilton ◽  
J. H. Healy
Keyword(s):  
Fault Plane ◽  
Nuclear Explosion ◽  
Test Site ◽  
Strike Slip ◽  
Nevada Test Site ◽  
Ground Zero ◽  
Fault Plane Solutions ◽  
Fault Movement ◽  
Near Surface ◽  
Earthquake Distribution

abstract The Benham nuclear explosion, a 1.1 megaton test 1.4 km beneath Pahute Mesa at the Nevada Test Site, initiated a sequence of earthquakes lasting several months. The epicenters of these shocks were located within 13 km of ground zero in several linear zones that parallel the regional fault trends. Focal depths range from near surface to 6 km. The earthquakes are not located in the zone of the major ground breakage. The earthquake distribution and fault plane solutions together indicate that both right-lateral strike-slip fault movement and dip-slip fault movement occurred. The explosion apparently caused the release of natural tectonic strain.

scholarly journals Seismic evidence for the tectonics of Central and Western Asia

1959 ◽  
Vol 49 (4) ◽  
pp. 369-378
Author(s):  
A. E. Scheidegger
Keyword(s):  
Fault Plane ◽  
Stress System ◽  
Motion Direction ◽  
Fault Plane Solutions ◽  
Small Areas ◽  
Mountain Ranges ◽  
Central Asian ◽  
Western Asia ◽  
Tectonic Motion

Abstract A statistical analysis of the null axes of the fault-plane solutions of earthquakes in any one area permits determination of the average tectonic motion direction of that area. In the present paper this method has been applied to areas in central and western Asia for which several hundred fault-plane solutions are readily available in the literature. The investigation yields the result that (seismically) calculated tectonic motion directions in a series of small areas that are part of a larger unit are consistent with each other and that there is in every case an excellent correlation with the tectonic motion of the area as postulated from geological studies. This appears to justify completely the seismic method. The seismically determined tectonic motion in central Asia appears to be mainly in a north-south direction. The motion refers to the present time (since the earthquakes occur at the present time), but it is the same as that postulated in geology for an explanation of the folding of the central Asian mountain ranges. This demonstrates that the stress system which created the central Asian mountains is active at the present time.

Seismicity in South Carolina

1988 ◽  
Vol 59 (4) ◽  
pp. 165-171
Author(s):  
Kaye M. Shedlock
Keyword(s):  
South Carolina ◽  
Compressive Stress ◽  
Coastal Plain ◽  
Fault Plane ◽  
Strike Slip ◽  
Fault Plane Solutions ◽  
Reservoir Induced Seismicity ◽  
Southeastern Us ◽  
Horizontal Compressive Stress ◽  
Shallow Crust

Abstract The largest historical earthquake in South Carolina, and in the southeastern US, occurred in the Coastal Plain province, probably northwest of Charleston, in 1886. Locations for aftershocks associated with this earthquake, estimated using intensities based on newspaper accounts, defined a northwest trending zone about 250 km long that was at least 100 km wide in the Coastal Plain but widened to a northeast trending zone in the Piedmont. The subsequent historical and instrumentally recorded seismicity in South Carolina images the 1886 aftershock zone. Except for a few scattered earthquakes and a swarm of shallow (≤ 4 km deep), small (ML ≤ 2.5), primarily reverse faulting earthquakes that occurred along the flanks of a granite pluton about 60 km northwest of Columbia, the seismicity in the Piedmont province has been associated with water level changes in reservoirs. Reservoir induced seismicity (RIS) is shallow (≤ 6 km deep), primarily strike-slip or thrust faulting corresponding to an inferred maximum horizontal compressive stress oriented approximately N 60° E. Instrumentally recorded seismicity in the Coastal Plain province occurs in 3 seismic zones or clusters: Middleton Place-Summerville (MPSSZ), Adams Run (ARC), and Bowman (BSZ). Approximately 68% of the Coastal Plain earthquakes occur in the MPSSZ, a north trending zone about 22 km long and 12 km wide, lying about 20 km northwest of Charleston. The hypocenters of MPSSZ earthquakes range in depth from near the surface to almost 12 km. Thrust, strike-slip, and some normal faulting are indicated by the fault plane solutions for Coastal Plain earthquakes. The maximum horizontal compressive stress, inferred from the P-axes of the fault plane solutions, is oriented NE-SW in the shallow crust (< 9 km deep) but appears to be diffusely E-W between 9 to 12 km deep. Although there is localized variability, the current seismicity and associated faulting in South Carolina probably represent a regional response to the NE-SW maximum horizontal compressive stress prevalent throughout eastern North America.

The Livermore Valley, California, sequence of January 1980

1981 ◽  
Vol 71 (2) ◽  
pp. 451-463
Author(s):  
B. A. Bolt ◽  
T. V. McEvilly ◽  
R. A. Uhrhammer
Keyword(s):  
Fault Plane ◽  
B Value ◽  
Strike Slip ◽  
Causal Connection ◽  
Fault Plane Solutions ◽  
Lateral Strike Slip ◽  
Marsh Creek ◽  
Long Duration ◽  
The University ◽  
Rapid Deployment

abstract At 19h00m09.46s UTC, on 24 January 1980, a strong earthquake (ML = 5.5) that caused a surprising amount of damage occurred north of Livermore Valley about 12 km to the southeast of Mt. Diablo, and was associated with surface rupture along the Greenville Fault. There was a foreshock (ML = 2.7) a minute and a half earlier and a sequence of 59 events (ML ≧ 2.5) in the ensuing 6 days. On 27 January at 02h33m35.96s, a larger magnitude earthquake occurred in the sequence (ML = 5.6). This second principal shock was located 14 km to the south of the first principal earthquake toward the southern end of the Greenville Fault. Preliminary estimates of the seismic moments of the two principal shocks are 5.3 × 1024 and 1.3 × 1024 dyne-cm, respectively. In addition to the lower seismic moment, the ML = 5.6 shock on 27 January exhibits a clearly focused radiation pattern, with large amplitudes toward the northeast. Field investigations after the first principal shock indicated surfaced rupture along the Greenville fault zone for at least 6 km, with both right-lateral strike-slip and some dip-slip motion with the northeast side up. Variable offsets on surface cracks suggested displacements of a few centimeters (with evidence of increases in some places after the second 27 January earthquake). There were eight earthquakes with ML ≧ 4.0 in the sequence up to 5 February 1980. No foreshocks near the Greenville Fault (ML ≧ 1.5) were observed by the University of California Seismographic Stations in the prior 3 months. Rapid deployment of field seismographs by a number of seismological organizations permitted precise locations and fault-plane solutions. Some results on seismicity are as follows. The rupture propagated over 15 km to the southeast along the Marsh Creek-Greenville faults on 24 January and stopped in the vicinity of Highway 580. This southern progression may have had some causal connection with the relatively high intensities reported near the southwest end of the Greenville Fault. The two principal shocks of the sequence have slight but significant differences in the fault-plane solutions; both are predominantly right-lateral strike-slip, but the strike of the northern one is N13°W, whereas the strike of the southern one is N39°W. This change in strike is not evident in the mapped strikes of the Marsh Creek and the Greenville faults. In contrast to the second principal earthquake, the first principal shock was followed by two others (ML &gt; 4.0) in rapid succession, one 53 sec and the other 97 sec after. This repetition gave a relatively long duration to the shaking on 24 January, and was commented on in felt reports. It may explain the greater intensity reported in many localities on 24 January compared to 27 January. The b value (0.64 ± 0.13) for the sequence is somewhat lower than the b = 0.70 ± 0.17 for the recent Coyote Lake earthquake sequence on the Calaveras Fault on 5 August 1979. There are fewer earthquakes than normal in the range 3.0 &lt; ML &lt; 4.0 in the Greenville sequence.

Aftershocks of the Managua, Nicaragua, earthquake of December 23, 1972

1974 ◽  
Vol 64 (4) ◽  
pp. 1005-1016
Author(s):  
C. J. Langer ◽  
M. G. Hopper ◽  
S. T. Algermissen ◽  
J. W. Dewey
Keyword(s):  
Fault Plane ◽  
Strike Slip ◽  
Fault System ◽  
Fault Plane Solutions ◽  
Lateral Strike Slip ◽  
Seismic Zones ◽  
The North ◽  
Primary Zone ◽  
Slip Displacement ◽  
Strain Release

abstract Epicenters determined from 164 of the Managua aftershocks define two seismic zones. The primary zone, which is 15 to 20 km in length and strikes northeast along the Tiscapa-Ciudad Jardin fault system, contains 80 per cent of the aftershock locations. A subsidiary zone, northwest of Managua, suggests strain release possibly related to the north-south striking San Judas fault. Depth of foci are principally in the upper 7 km for both zones. Composite fault-plane solutions indicate a predominate left-lateral strike-slip displacement; the preferred planes for each zone agree with the strike of surface fractures or previously mapped faults.

Aftershocks of an M = 4.2 earthquake in Hawaii and comparison with long-term studies of the same volume

1985 ◽  
Vol 75 (3) ◽  
pp. 759-777
Author(s):  
Martha Kane Savage ◽  
Robert P. Meyer
Keyword(s):  
Main Shock ◽  
Rift Zone ◽  
Fault Plane ◽  
Linear Region ◽  
Fault Plane Solutions ◽  
One Dimensional ◽  
Delay Times ◽  
The Relationship ◽  
Long Term Studies

Abstract Study of the aftershocks recorded in a 3-hr period after a 4.2 magnitude event on the East Rift Zone of Kilauea volcano, Hawaii, on 12 April 1982 shows that the aftershocks occurred on different planes than the main shock, probably as a result of stress redistribution; the aftershock locations are probably controlled by preexisting structures. This study also suggests that these relatively small aftershocks occurred in the same seismicity patterns as larger events recorded in the same volume over a period of 10 yr. Slips on most of the aftershocks and the main shock are in the same direction, perpendicular to the East Rift Zone, as has been found in studies of other, larger earthquakes. However, fault-plane solutions varied more, as did the tensional axes, and several of the smaller events showed movement in the opposite direction from the main shock and the rest of the aftershocks, suggesting some rebound was occurring near the edges of the aftershock zone. Because ten times as much energy was released in the aftershocks in a narrow linear region as elsewhere, and since the main shock epicenter was oceanward of all the aftershocks, we suggest that rupture began at the main shock hypocenter and propagated landward, implying an almost “one-dimensional” fault. For the aftershocks, the relationship between moment and magnitude was: log M0 = (1.18 ± 0.17) ML + (17.3 ± 0.17). Differences in amplification lead to site differences of up to 0.8 units in local magnitude and 1.5 orders of magnitude in energy release. These correlated somewhat with station time corrections in that the stations with the longest delay times also had greatest amplification.

Relocation of Koyna earthquakes

1980 ◽  
Vol 70 (5) ◽  
pp. 1849-1868
Author(s):  
B. K. Rastogi ◽  
P. Talwani
Keyword(s):  
Fault Plane ◽  
Seismic Velocity ◽  
Landsat Imagery ◽  
Velocity Model ◽  
Strike Slip ◽  
Normal Faulting ◽  
Large Area ◽  
Fault Plane Solutions ◽  
Lateral Strike Slip ◽  
Induced Earthquake

abstract The Koyna earthquake of December 10, 1967 was the most damaging reservoir-induced earthquake. It was followed by a long sequence of earthquakes which is still continuing. Precise locations of the Koyna earthquakes have been very much disputed as different locations of the main earthquake and stronger aftershocks were obtained by various workers. Over 1,500 epicenters of Koyna earthquakes through 1973 were obtained by Guha et al. (1974). They cover a large area in a diffused pattern. In view of the continuing seismicity and a recently obtained seismic velocity model, the larger events (ML ≧ 4.0) and about 300 selected smaller events (ML &lt; 4.0) were relocated. The relocated epicenters show some concentration and suggest the possibility of two trends in the NNE and NW directions. There is a NNE trend of epicenters near the dam and another about 20 km west of the reservoir. The NW trend cuts through these NNE trends. The events were grouped to obtain their composite fault-plane solutions which indicate left-lateral strike-slip faulting along the NNE faults and normal faulting in the NW direction. Faults observed in the LANDSAT imagery match with these trends.

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