Active Tectonics Impact on Society (1986) / Chapter Skim
Currently Skimming:
3. Evaluation of Active Faulting and Associated Hazards
3. Evaluation of Active Faulting and Associated Hazards
Pages 45-62
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 45... ...
BURTON SLEMMONS arid CRAIG M DEPOLO University of Nevada, Reno ABSTRACT Active faulting is a geologic hazard with a causative relation to earthquakes and associated strong ground motion, surface faulting, tectonic deformation, landslides and rockfalls, liquefaction, tsunamis, and seiches.
|
From page 46... ...
Importance to Society Most evaluations of active faults are conducted at or near plate boundaries, where consideration of design, siting, zoning, communication, and response to earthquake hazards is necessary for all types of major eng~neering structures in order to reduce potential loss of life, injury, or property damage. The seismic motion or deformation effects on facilities such as nuclear generators, dams, communication centers, and other lifelines is critical because of great potential harm to society.
|
From page 47... ...
, and surface exposure. HAZARDS RELATED TO FAULTS Earthquake and Ground Motion Perhaps the best-known hazards of active faulting are the destructive effects of earthquake shaking, often called "strong ground motion." Sudden movement along a fault or fault zone radiates elastic waves that are generally strongest near the causative fault and taper off or attenuate away from the fault.
|
From page 48... ...
Surface displacement can occur gradually in areas of tectonic creep and nontectonic fluid withdrawal. In California, several faults are undergoing tectonic creep, with a maximum reported creep of 3.2 cm/yr along the San Andreas Fault in San Benito County (Burford and Harsh, 1980~.
|
From page 49... ...
Closer inspection of interplate regions reveals smaller "microplate" tectonic domains characterized by a particular faulting style, such as the Basin and Range province in the western United States. InterpZate Regions These regions have many active faults with a potential for future displacements and associated earthquake activity.
|
From page 50... ...
Recognition and detailed mapping of historical and Quaternary faults in many zones of neotectonic activity, particularly at or near plate boundaries, have led to recent improvements in the delineation of active faults. In addition, the possible reactivation of intraplate faults such as the Meers Fault has emphasized the need to re-examine other faults and folds in central and eastern United States.
|
From page 51... ...
Many active faults have associated seismicity, including the Calaveras, Hayward, and central San Andreas Fault zones of central California, which, however, may only indicate the creeping segments of these faults. Other sections of the San Andreas Fault system that are not currently creeping are not clearly delineated by small earthquakes.
|
From page 52... ...
presents a good summary and review of Quater FIGURE 3.2 Relation between time or recurrence interval between earthquakes, earthquake magnitude, and slip rate across the fault zone. This chart assumes that most of the energy is released by seismogenic rather than aseismic activity and that the average displacement is one half the maximum.
|
From page 53... ...
(TREMELY LOW RATES OF ACTIVITY LOW ACTIVITY WITH SPARSE GEOMORPHIC EVIDENCE OF ACTIVITY C MODERATE ACTIVITY WITH I4ODERATE TO WELL DEVELOPED GEOt~RPHIC EVIDENCE OF ACTIVITY B HIGH ACTIVITY RATE WITH ABUNDANT BUT SOMETIMES DISCONTINUOUS EVIDENCE OF ACTIVITY A VERY HIGH ACTIVITY RATE WITH EXCEI I FNT GEOMORPHIC EVIDENCE AS AT MAJOR PLATE BOUNDARIES M EXTREME RATE OF ACTIVITY, SE1~1 DEVELOPED, EVEN ON MAJOR PLATE BOUNDARIES; EXAPPLES INCLUDE SUBDUCTION ZONES AAA 5L'P RAT' S"L£ 53 FIGURE 3.3 Geomorphic features related to active faulting. (Chapter 11, this volume)
|
From page 54... ...
We have assumed that the average displacement is one-half the maximum displacement. EARTHQUAKE SIZE AND ACTIVE FAULT PARAMETERS Earthquake Magnitudes and Moment Magnitude Earthquake magnitude scales are one of the most important earthquake size source parameters used today in seismology and active-tectonic studies.
|
From page 55... ...
(1980) studied the seismicity and behavior of the San Andreas Fault zone in central California where strain release is characterized by creep and moderate earthquakes.
|
From page 56... ...
EARTHQUAKE RECURRENCE ESTIMATION Recurrence Models Earthquake recurrence intervals can vary markedly from fault to fault. Historical seismicity of the Parkfield segment of the San Andreas Fault system suggests a recurrence rate of 21 + 4 yr (Bakun and McEvilly, 1984)
|
From page 57... ...
Specific model for the Bear ValleyLimekiln Road section of the San Andreas Fault in central California. (From Bakun et al., 1980.)
|
From page 58... ...
Many existing engineered structures may have inadequate design for earthquakes of magnitude 7.5, 8.0, or8.5. Implications of the Meers Fault, Oklahoma The Meers Fault (Figure 3.
|
From page 59... ...
Pleistocene fault activity along the Kentucky River Fault zone has been suggested by VanArsdale and Sergeant (1985~. They examined trenches in the Plio-Pleistocene terrace deposits along the Kentucky River Fault zone and found the deposits folded, faulted, and injected with clay dikes.
|
From page 60... ...
. Displacements on the Imperial, Superstition Hills and the San Andreas Faults triggered by the Borrego Mountain earthquake, U.S.
|
From page 61... ...
. Fault behavior and characteristic earthquakes: Examples from the Wasatch and San Andreas Faults, J
|
From page 62... ...
. Earthquake recurrence intervals on the San Andreas Fault, California, Geol.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.