Archive for October, 2012

Hayward-Rodgers Creek Fault Hazard, Northern California

Posted by cdj On October - 22 - 2012
The U.S. Geological Survey (USGS) advise that the probability occurrence in California of one or more Mw=6.7 or larger earthquakes (the 1994 Northridge earthquake was Mw=6.7) over the next 30 years is 99%. The state’s likelihood of a more powerful earthquake (Mw=7.5 or greater) in the next 30 years is 46%. In Northern California, the most likely source of a Mw=6.7 or larger earthquake is the Hayward-Rogers Creek Fault. The USGS also concluded that 3 Mw=5.0 or greater earthquakes will occur in California every year and a Mw=6.0 or greater will occur every 1.5 years.

Probable Earthquake Hazard - SF Bay

The last significant earthquake event on the Hayward Fault in Northern California was, October 21, 1868 when the area was sparsely populated. The USGS developed a shaking intensity map of the 1868 Hayward earthquake from reliable reports of the event. Today, the Hayward-Rogers Creek Fault has a 31% probability of Mw=6.7 or greater earthquake occurring in next 30 years. Today this strong shaking would occur in a heavily populated and economically developed area of the state.

A variety of sources for personal emergency preparation exist such as this 72hours.org site.

Changes in Seismicity Following (Large) Earthquakes

Posted by cdj On October - 17 - 2012

A USGS sponsored team recently published their study results of the extent to which the 2004, (M=9.2) Sumatra earthquake altered seismicity in the Andaman backarc rift-transform system near Sumatra, Indonesia. The study suggests that stresses imparted by the great earthquake, which struck along the Sunda trench where the Indian-Australian plate undergoes oblique subduction, may have shut down existing transform fault activity and activated some rifts up to 400 km away from the source of the earthquake. Some implications for triggered seismicity are discussed.

The Quebec Bridge, 1906-1917

Posted by cdj On October - 5 - 2012

On Monday, September 20th, 1917, the last suspended span was successfully lifted and connected at all points and the “Quebec Bridge” carrying the transcontinental line of the Canadian railways over the St. Lawrence River near Quebec City (Canada) was completed. Building the Quebec Bridge was a complicated engineering and construction feat fraught with difficulty and disaster. On August 29th, 1907, the first attempt at building the Quebec Bridge failed disastrously as the cantilever steel structure under construction collapsed into the St. Lawrence River taking 75 lives. Near the completion of the second Quebec Bridge on September 11, 1916, another collapse occurred while workmen attempted to hoist the suspended span up from the river below. For further reading on this topic, the well-illustrated history of building the Quebec Bridge is described in the 1918 book, “The Quebec Bridge”.

Quebec Bridge, 1917

Quebec Bridge, 1917

Quebec Bridge, 1917

In the Engineering News Record of September 27, 1917 it was observed:

“…Before closing the final chapter in the design and erection of this remarkable structure, it is proper to record the debt that bridge-builders owe to the work at Quebec. It has advanced greatly our knowledge of the problems of large compression members and of tension bars. The effects of distortion in tresses were explored farther than before and means devised for dealing with such effects. Much knowledge has been added to our store of experience on the assembly of heavy members, while new standards were set as to degree of precision and finish in shopwork. Then there is, beyond all this, a great gain in our general grasp of the problem of very large bridges as to practicability and cost. But these are the gains of the profession as a whole. To the individual engineer the great value of the achievement lies in the inspiration emanating from the courage of the men who have erected on the failure of 1907 and the loss of 1916 this greatest of bridges- and in so doing not only have erected a monument to themselves and their courage and ability, but have vindicated the profession before a doubting world.”

Bridge Span Comparisons to Quebec Bridge, 1917

OpenSees Version 2.4.0 now available -

Posted by cdj On October - 4 - 2012

A new release of OpenSees, — the Open System for Earthquake Engineering Simulation, a copyrighted, open-source software framework for simulating the seismic response of structural and geotechnical systems and developed as the computational platform for research in performance-based earthquake engineering at the Pacific Earthquake Engineering Research Center — is now available. The revised software change log indicates some significant additions including: new classes for thermo-mechancial (fire) analysis (Steel01Thermal, Concrete02Thermal, FiberSection2dThermal, DispBeamColumn2dThermal, BeamThermalLoad, FireLoadPattern created by Liming Jiang and the OpenSees Developers Group, Institute for Infrastructure and Environment, School of Engineering at the University of Edinburgh ) and various new analytical models developed at McGill University (D. Lignos), University of Washington (P. Arduino et al), Tsinghua University (Rui Wang), University of Padua (L.Tesser) and a new triple friction pendulum element (created by N. Dao and K. Ryan, University of Nevada, Reno).

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