scholarly journals Rupture directivity and fault plane determination from analysis of rupture duration using broadband P-waves of the September 2018 M w 7.5 Palu, Indonesia earthquake

2021 ◽  
Vol 1125 (1) ◽  
pp. 012002
Author(s):  
Madlazim ◽  
T Prastowo ◽  
M N Fahmi
Keyword(s):  
Fault Plane ◽  
Rupture Directivity ◽  
P Waves ◽  
Rupture Duration

Source inversion of the 1988 Upland, California, earthquake: Determination of a fault plane for a small event

1990 ◽  
Vol 80 (3) ◽  
pp. 507-518 ◽  
Author(s):  
Jim Mori ◽  
Stephen Hartzell
Keyword(s):  
Green Function ◽  
Fault Plane ◽  
Least Squares Method ◽  
Source Area ◽  
Rupture Velocity ◽  
P Waves ◽  
Waveform Data ◽  
Empirical Green Function ◽  
Finite Fault ◽  
Short Period

Abstract We examined short-period P waves to investigate if waveform data could be used to determine which of two nodal planes was the actual fault plane for a small (ML 4.6) earthquake near Upland, California. We removed path and site complications by choosing a small aftershock (ML 2.7) as an empirical Green function. The main shock P waves were deconvolved by using the empirical Green function to produce simple far-field displacement pulses. We used a least-squares method to invert these pulses for the slip distribution on a finite fault. Both nodal planes (strike 125°, dip 85° and strike 221°, dip 40°) of the first-motion focal mechanism were tested at various rupture velocities. The southwest trending fault plane consistently gave better fitting solutions than the southeast-trending plane. We determined a moment of 4.2 × 1022 dyne-cm. The rupture velocity, and thus the source area could not be well resolved, but if we assume a reasonable rupture velocity of 0.87 times the shear wave velocity, we obtain a source area of 0.97 km2 and a stress drop of 38 bars. Choice of a southwest-trending fault plane is consistent with the trend of the nearby portion of the Transverse Ranges frontal fault zone and indicates left-lateral motion. This method provides a way to determine the fault plane for small earthquakes that have no surface rupture and no obvious trend in aftershock locations.

A comparison of some S-wave studies of earthquake mechanisms

1961 ◽  
Vol 51 (2) ◽  
pp. 277-292
Author(s):  
William Stauder ◽  
Adams W. M.
Keyword(s):  
Fault Plane ◽  
Analytical Techniques ◽  
P Wave ◽  
Graphical Methods ◽  
S Wave ◽  
Fault Plane Solutions ◽  
P Waves ◽  
S Waves ◽  
Analytical Technique ◽  
Direction Of Polarization

Abstract Graphical and analytical techniques for using S-waves in focal mechanism studies are compared. In previous applications the analytical technique has shown little or no agreement with the results of fault-plane solutions from P-waves, whereas for other groups of earthquakes the graphical methods have shown good agreement between the S-waves and the P-wave solutions. It is shown that the graphical and analytical techniques are identical in principle and that when the graphical methods are applied to the same three earthquakes to which the analytical technique had been applied the identical results are obtained. Closer examination of the graphical presentation of the data, however, shows that the disagreement between the S-waves and the fault plane solutions from P is largely apparent. The discrepancy follows upon the peculiar scatter in the S-wave data and the chance occurrence of observations of S at stations located along closely parallel planes of polarization of S. Once this is understood, it is seen that the direction of polarization of S-waves is in substantial agreement with the methods of analysis of focal mechanisms from P-waves, and that the data are consistent with a simple dipole as the point model of the earthquake focus.

Rupture directivity and slip distribution of the M 4.3 foreshock to the 1992 Joshua Tree earthquake, Southern California

1996 ◽  
Vol 86 (3) ◽  
pp. 805-810
Author(s):  
Jim Mori
Keyword(s):  
Southern California ◽  
High Stress ◽  
Slip Distribution ◽  
Rupture Directivity ◽  
P Waves ◽  
The North ◽  
Network Deconvolution ◽  
Northern Edge ◽  
Inversion Procedure ◽  
East West

Abstract Details of the M 4.3 foreshock to the Joshua Tree earthquake were studied using P waves recorded on the Southern California Seismic Network and the Anza network. Deconvolution, using an M 2.4 event as an empirical Green's function, corrected for complicated path and site effects in the seismograms and produced simple far-field displacement pulses that were inverted for a slip distribution. Both possible fault planes, north-south and east-west, for the focal mechanism were tested by a least-squares inversion procedure with a range of rupture velocities. The results showed that the foreshock ruptured the north-south plane, similar to the mainshock. The foreshock initiated a few hundred meters south of the mainshock and ruptured to the north, toward the mainshock hypocenter. The mainshock (M 6.1) initiated near the northern edge of the foreshock rupture 2 hr later. The foreshock had a high stress drop (320 to 800 bars) and broke a small portion of the fault adjacent to the mainshock but was not able to immediately initiate the mainshock rupture.

The Hebgen Lake, Montana, earthquake of August 18, 1959: P waves

1962 ◽  
Vol 52 (2) ◽  
pp. 235-271
Author(s):  
Alan Ryall
Keyword(s):  
Travel Time ◽  
Sierra Nevada ◽  
Fault Plane ◽  
Time Curve ◽  
P Waves ◽  
Arrival Times ◽  
The Pacific ◽  
First Motion ◽  
Plane Solution ◽  
The Pacific Ocean

ABSTRACT The instrumental epicenter of the Hebgen Lake earthquake is found to lie within the region of surface faulting. The depth of focus had a maximum value of 25 kilometers. Times of P are studied in detail for epicentral distances less than 13 degrees. The apparent scatter of arrival times from 700 to 1400 kilometers can be explained by variations of the velocity of Pn between the physiographic provinces of the western United States. A comparison of observations for the Hebgen Lake earthquake with published times for blasts in Nevada and Utah indicates that the velocity of Pn in the central and eastern Basin and Range is about 7.5 km/sec, and that the crust in that region thickens toward the east and thins toward the south. A comparison of apparent velocities in northern California, in directions parallel and transverse to the structure, indicates that the crust thins by about 19 kilometers, from the edge of the Sierra Nevada to the Pacific Ocean. A discontinuity is observed in the travel-time curve at a distance of 24–25 degrees. Arrivals of P waves in the range 65–128 degrees fall on two parallel travel-time branches; this multiplicity in the travel-time curve may be related to repeated motion at the source. Travel-times of PKIKP appear to deviate from published curves. The fault-plane solution for the Hebgen Lake earthquake, together with a consideration of the first motion at Bozeman, Montana, indicates a focal mechanism of the dipole, or fault, type. The strike and dip of the instrumental fault plane agree well with observed ruptures at the surface.

Strong Ground Motion Attributes of the 2010 Mw 8.8 Maule, Chile, Earthquake

2012 ◽  
Vol 28 (1_suppl1) ◽  
pp. 19-38 ◽  
Author(s):  
Rubén L. Boroschek ◽  
Víctor Contreras ◽  
Dong Youp Kwak ◽  
Jonathan P. Stewart
Keyword(s):  
Ground Motion ◽  
Fault Plane ◽  
Soft Soil ◽  
Strong Motion ◽  
Response Spectra ◽  
Rupture Directivity ◽  
Magnitude Scaling ◽  
Chile Earthquake ◽  
Rupture Distance ◽  
Strong Ground

The Mw 8.8 Maule, Chile, earthquake produced 31 usable strong motion recordings from currently accessible arrays over a rupture distance range of 30 to 700 km. Site conditions range from firm rock to soft soil but are most often competent soil (NEHRP Category C or C/D). Most of the data were recorded on analogue instruments, which was digitized and processed with low- and high-cut filters designed to maximize the usable frequency range of the signals. The stations closest to the fault plane do not exhibit evidence of ground motion polarization from rupture directivity. Response spectra of nearby recordings on firm ground and soft soil indicate pronounced site effects, including several cases of resonance at site periods. A prior GMPE for interface subduction events captures well the distance scaling and dispersion of the data, but under-predicts the overall ground motion level, perhaps due to too-weak magnitude scaling.

scholarly journals A holistic seismotectonic model of Delhi region

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Brijesh K. Bansal ◽  
Kapil Mohan ◽  
Mithila Verma ◽  
Anup K. Sutar
Keyword(s):  
Strain Energy ◽  
Fault Plane ◽  
Near Field ◽  
Energy Estimates ◽  
The West ◽  
Fault Plane Solutions ◽  
Northern India ◽  
Structural Environment ◽  
Reverse Faulting ◽  
Using Data

AbstractDelhi region in northern India experiences frequent shaking due to both far-field and near-field earthquakes from the Himalayan and local sources, respectively. The recent M3.5 and M3.4 earthquakes of 12th April 2020 and 10th May 2020 respectively in northeast Delhi and M4.4 earthquake of 29th May 2020 near Rohtak (~ 50 km west of Delhi), followed by more than a dozen aftershocks, created panic in this densely populated habitat. The past seismic history and the current activity emphasize the need to revisit the subsurface structural setting and its association with the seismicity of the region. Fault plane solutions are determined using data collected from a dense network in Delhi region. The strain energy released in the last two decades is also estimated to understand the subsurface structural environment. Based on fault plane solutions, together with information obtained from strain energy estimates and the available geophysical and geological studies, it is inferred that the Delhi region is sitting on two contrasting structural environments: reverse faulting in the west and normal faulting in the east, separated by the NE-SW trending Delhi Hardwar Ridge/Mahendragarh-Dehradun Fault (DHR-MDF). The WNW-ESE trending Delhi Sargoda Ridge (DSR), which intersects DHR-MDF in the west, is inferred as a thrust fault. The transfer of stress from the interaction zone of DHR-MDF and DSR to nearby smaller faults could further contribute to the scattered shallow seismicity in Delhi region.

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