scholarly journals Determination of earthquake source mechanisms using teleseismic 30-140 s waves: The January 17, 1994, Northridge earthquake

1997 ◽  
Vol 102 (B4) ◽  
pp. 8159-8169 ◽  
Author(s):  
Jiajun Zhang ◽  
Keiko Kuge ◽  
Thorne Lay ◽  
Seiji Tsuboi
Keyword(s):  
Earthquake Source ◽  
Northridge Earthquake ◽  
S Waves ◽  
Source Mechanisms ◽  
1994 Northridge Earthquake

Nonlinear ground-motion amplification by sediments during the 1994 Northridge earthquake

Nature ◽  
10.1038/37586 ◽  
1997 ◽  
Vol 390 (6660) ◽  
pp. 599-602 ◽  
Author(s):  
Edward H. Field ◽  
Paul A. Johnson ◽  
Igor A. Beresnev ◽  
Yuehua Zeng
Keyword(s):  
Ground Motion ◽  
Northridge Earthquake ◽  
Ground Motion Amplification ◽  
1994 Northridge Earthquake

scholarly journals Responses of dipole-source reflected shear waves in acoustically slow formations

2019 ◽  
Author(s):  
Hao Wang ◽  
Ning Li ◽  
Caizhi Wang ◽  
Hongliang Wu ◽  
Peng Liu ◽  
...  
Keyword(s):  
Finite Difference Time Domain ◽  
Dipole Source ◽  
Sh Wave ◽  
S Wave ◽  
High Fracture ◽  
S Waves ◽  
Angle Fracture ◽  
Dip Angle ◽  
Difference Time

Abstract In the process of dipole-source acoustic far-detection logging, the azimuth of the fracture outside the borehole can be determined with the assumption that the SH–SH wave is stronger than the SV–SV wave. However, in slow formations, the considerable borehole modulation highly complicates the dipole-source radiation of SH and SV waves. A 3D finite-difference time-domain method is used to investigate the responses of the dipole-source reflected shear wave (S–S) in slow formations and explain the relationships between the azimuth characteristics of the S–S wave and the source–receiver offset and the dip angle of the fracture outside the borehole. Results indicate that the SH–SH and SV–SV waves cannot be effectively distinguished by amplitude at some offset ranges under low- and high-fracture dip angle conditions, and the offset ranges are related to formation properties and fracture dip angle. In these cases, the fracture azimuth determined by the amplitude of the S–S wave not only has a $180^\circ $ uncertainty but may also have a $90^\circ $ difference from the actual value. Under these situations, the P–P, S–P and S–S waves can be combined to solve the problem of the $90^\circ $ difference in the azimuth determination of fractures outside the borehole, especially for a low-dip-angle fracture.

A numerical study of the interaction between unsteay free-stream disturbances and localized variations in surface geometry

1989 ◽  
Vol 209 ◽  
pp. 285-308 ◽  
Author(s):  
R. J. Bodonyi ◽  
W. J. C. Welch ◽  
P. W. Duck ◽  
M. Tadjfar
Keyword(s):  
Numerical Solutions ◽  
Free Stream ◽  
Stokes Equations ◽  
Numerical Study ◽  
Navier Stokes ◽  
Surface Geometry ◽  
Navier Stokes Equations ◽  
S Waves ◽  
Tollmien Schlichting

A numerical study of the generation of Tollmien-Schlichting (T–S) waves due to the interaction between a small free-stream disturbance and a small localized variation of the surface geometry has been carried out using both finite–difference and spectral methods. The nonlinear steady flow is of the viscous–inviscid interactive type while the unsteady disturbed flow is assumed to be governed by the Navier–Stokes equations linearized about this flow. Numerical solutions illustrate the growth or decay of the T–S waves generated by the interaction between the free-stream disturbance and the surface distortion, depending on the value of the scaled Strouhal number. An important result of this receptivity problem is the numerical determination of the amplitude of the T–S waves.

The 1994 Northridge Earthquake Disaster Response: The Local Emergency Medical Services Agency Experience

1996 ◽  
Vol 11 (3) ◽  
pp. 172-179 ◽  
Author(s):  
Samuel J. Stratton ◽  
Virginia Price Hastings ◽  
Darlene Isbell ◽  
John Celentano ◽  
Miguel Ascarrunz ◽  
...  
Keyword(s):  
Public Health ◽  
Emergency Medical Services ◽  
Disaster Response ◽  
Communication Systems ◽  
Medical Services ◽  
Northridge Earthquake ◽  
Power Sources ◽  
Incident Command ◽  
Emergency Medical ◽  
1994 Northridge Earthquake

AbstractIntroduction:This paper describes the 1994 Northridge earthquake experience of the local emergency medical services (EMS) agency. Discussed are means that should improve future local agency disaster responses.Methods:Data reported are descriptive and were collected from multiple independent sources, and can be reviewed publicly and confirmed. Validated data collected during the disaster by the Local EMS Agency also are reported.Results:The experience of the Los Angeles County EMS Agency was similar to that of earthquake disasters previously reported. Communication systems, water, food, shelter, sanitation means, power sources, and medical supplies were resources needed early in the disaster. Urban Search and Rescue Teams and Disaster Medical Assistance Teams were important elements in the response to the Northridge earthquake. The acute phase of the disaster ended within 48 to 72 hours and public health then became the predominant health-care issue. Locating community food and water supplies near shelters, providing transportation to medical care, and public-health visits to shelter locations helped prevent the development of long-term park encampments. An incident command system for the field, hospitals, and government responders was necessary for an organized response to the disaster.Conclusion:Disaster preparedness, multiple forms of reliable communication, rapid mobilization of resources, and knowledge of available state and federal resources are necessary for a disaster response by a local EMS agency.

Determination of point source mechanisms

2014 ◽  
pp. 108-134 ◽  
Author(s):  
Agustin Udias ◽  
Raul Madariaga ◽  
Elisa Buforn
Keyword(s):  
Point Source ◽  
Source Mechanisms

scholarly journals The seisniicity of Iran. The Silakhor (Luristan) earthquake of 23rd Ianuary, 1909 (Part II)

2010 ◽  
Vol 27 (3-4) ◽  
Author(s):  
N. N. AMBRASEYS
Keyword(s):  
Tectonic Activity ◽  
The World ◽  
Source Mechanisms ◽  
The Difference ◽  
Large Earthquakes ◽  
Remote Part

This paper shows t h a t given certain conditions it is perfectly feasible to study an earthquake that occurred three-quarters of a century ago in a remote part of the world. Also, it shows that there are many large earthquakes which, because of lack of interdisciplinary efforts to study such events, have remained hitherto little known or totally unknown. The case of the Silakhor earthquake revealed deficiencies in the determination of epicentres by ISS and Gutenberg; the difference between macroseismic and instrumental position for the Silakhor earthquake is 380 kilometres, a difference which lias caused a serious problem in the assessment of seisniicity of Iran. Accurate macroseismic d a t a may be used to minimize bias in t h e instrumental relocation of the larger events and to study source mechanisms. Untili this study was undertaken, the faulting associated with the Silakhor earthquake was totally unknown. Even more important t h a n the value of recent faulting for its significance in resolving ambiguities in t h e choice of the t r u e source parametres, is the information that can be gleaned from evidence for the mechanism of earthquakes that occurred long before t h e advent of modern seismology and in particular, for the pattern of recent tectonic activity.

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