Dr.Ross Stein is one of well-known scientists providing an understanding modelling of stress modelling due to larger earthquakes. We will discuss one of his paper as:
Paper: Earthquake Conversation
The presentation based on the paper above is prepared and presented by Akram. Now, it is online for one to reach from:
Dr. Stein's CV is given in below:
Phone: (650) 329-4840 e-mail: rstein@usgs.gov
Mailing address: 345 Middlefield Rd MS 977 Menlo Park, CA-94025
Ross Stein
My research focuses upon how earthquakes interact through the transfer of stress. Examples of such interaction include the progression of mainshocks along a fault, aftershocks, seismic quiesence, and earthquake clustering. My collaborators and I are interested in how one earthquake can promote subsequent shocks at some sites and inhibit them in others.
This work is driven by an attempt to deepen our understanding of the physics of earthquakes, and a desire to develop a new way to make probabilistic hazard assessments. Our tools are seismology, geophysics, elasticity theory, structural geology, and geomorphology.
In addition, I study the deformation of the earth's surface associated with earthquakes, fault creep, and volcanic processes. This work seeks to infer rupture and fault geometry, and to understand the relationship between earthquake deformation and geologic structures. Our tools are classical and space geodesy. Key interests are blind thrust faults, high-angle normal faults, and magmatic inflation and collapse.
My work is currently funded by a Cooperative R&D Agreement with Swiss Re, the world's second largest insurance company; and through a series of research grants from NASA. My first R&D project with Swiss Re was a study of the earthquake threat to Istanbul in the wake of the 1999 Izmit shock; the current Swiss Re project assesses the earthquake hazard for Tokyo, and with participation by several leading Japanese scientists. A 1996-2001 R&D project earthquake hazards in the San Francisco Bay area was carried out with PG&E. Other recent studies were funded by U.S. Office of Foreign Disaster Assistance and FEMA.
Over the past several years, I have participated in documentary films, including 'Killer Quake' (NOVA, 1995), 'Great Quakes: Turkey' (Discovery Channel, 2001), 'Earthquake Storms' (BBC, 2003), and an IMAX film, 'Forces of Nature' (National Geographic), which wass released in summer 2004. Click here to see an article about 'Forces of Nature' in the Mercury News.
An interview with Ross Stein published at ISI Special Topics, December 2003.
This message has been edited by DEPREM on May 8, 2005 12:13 AM
The idea in this paper is easy to follow due its logical progression. An earthquake causes tremors that add stress to an earthquake prone area close by.Faulty planes respond to any thing that would increase the stress causing them to grind and slid shaking the earth above them. The cause of the added stress might as well be another earthquake “near by”. If the theory is sound then the world could be alerted of the approximate time and location of the next destroyer.
Q.1) Is there enough evidence of such theory other than the ones related to the San Andrea’s fault?
The paper seems only to talk about that part of the world.
Q.2) Would it matter if the earthquake is a long a strike-slip fault formation or underneath a convergent zone?
The paper doesn’t specifically take about the different kinds of earthquakes. However, it seems that the author believes of the simple theory that any where in the world if there two earthquake-prone fault then they’ll eavesdrop on each other.
Q.3) Could this production be the next forecast after the daily news, next to weather forecast?
Possibly, nowadays earthquakes are happening all over the world. Although, the cause of these earthquakes might be follow other reasons, such as the mantle loosing it viscosity.
Well, the paper does seem to talk about only the San Andreas Fault area, But the people are working on stress changes for different areas, not only on strike slip regimes,but also on thrusting and normal faulting regimes.
Q.2
the stress conditions will vary from regimes to regimes, and also the changes in coulomb failure will vary, depending on the strike slip, thrust or normal regimes.Like for the same order magnitude stress changes, that is, the coulomb failure stress change produced by the source earthquake, being the order of magnitude 10-2 MPa, if the ambient stress level is high ( as for strike slip earthquakes), there is almost no evident effect produced by such small perturbation. On the other hand, if the ambient stress level is low (as for thrust earthquakes), the small stress perturbations play a mole important role.
Explain how aftershocks generated in North America as per the author interpretation.
Answer:
Along the San Andreas Fault, for instance, the plate carrying North America is moving south relative to the one that underlies the Pacific Ocean. As the two sides move in opposite directions, shear stress is exerted parallel to the plane of the fault, as the rocks on opposite sides of the fault press against each other; they form second stress, perpendicular to the fault plane. When the shear exceeds the frictional resistance on the fault or when the stress pressing the two sides of the fault together is eased releasing tremendous energy. But because stress cannot simply disappear, it must distribute some where along the same fault or to nearby faults, which causes aftershocks.
Question #2:
What is the renewal probability forecast?
Answer:
It is a more refined forecast that predicts that the chances of a damaging shock climb as more time passes since the last one struck. This based on the assumption that stress along a fault increases gradually in the wake of a major earthquake.
Question #3:
What is the author’s forecast method main aspect?
Answer:
He builds the probabilities associated with earthquakes interactions on top of the renewal method by including the effects of stress changes imparted by nearby earthquakes.
I agree, how you think that author described the origin of aftershocks.as the author also told that the earthquakes can occur in the shadow zones as well as triggered zones.
Q#1: What happen when the shear stress exceeds the frictional resistance on the fault or when the stress pressing the tow sides of the fault?
A#1: The rocks on either side will slip past each other suddenly, releasing tremendous energy in the form of an earthquake.
Q#2: Explain how come in Turkey and in southern California that even tiny stress changes can have momentous effects, both calming and catastrophic?
A#2: Seismicity never shuts off completely in the shadow zones, nor does in turn on completely in the trigger zones .Instead the rate of seismicity merely drops in the shadows or climbs in the trigger zones relative to the preceding rate in the area.
Q#3: What the author and his colleagues observe after mapping the locations of Landers, Big Bear and hundreds of other California earthquakes?
A#3: They notice a remarkable pattern in the distribution not only of true aftershocks but also of other, smaller earthquakes that follow a main shock by days, weeks or even years.
I agree, as whenever the shear stress exceed the friction, slip will occur and cause an earthquake.
Q.2
Upto some extent I agree with your answer , But what i think is that earthquake from the main shock can both reduce and enhance the regional stress conditions/. In case if it raises, the earthquake will happen and when it decreases, there are very less chances that we'll have an earthquake there. That's the calming and catastrophic effects of the main earthquake, that either it can cause some earthquakes on other faults or it can inhibit the seismicity on other faults.
Q:1) Are earthquakes the only mechanism in which stresses are generated and released?
A:1) I believe that there are other factors that contribute to the generation and/or release of stress. One might be the behavior of the mantle beneath. This includes the convection regimes and the distribution of mass within the earth.
Q:2) Could we estimate the stresses in the earth accurately? In other words, how accurate is the “Coulomd stress change” map that the author presented in his paper? Are they accurate enough for the purpose of earthquake forecasting?
A:2) I am not sure how accurate these maps are because I don’t know the method used to generate them, however, the author did mention that he believes that very small change in stress regime (as little as 1/8 of the pressure required to inflate a car’s tire!!) could trigger as earthquake. If that is the case, then could these maps be reliable for the purpose of earthquake forecasting? I tend to believe otherwise.
Ali, This is great. Your students did a wonderful job with the paper. The SciAm editor added that Istanbul was the capital of Turkey, and she is very embarrassed by this mistake.
If any of your students want to go deeper, they can check my web site below, which includes the most recent work on this subject and a new paper (Toda et al, JGR, 2005) with 3 animations included.
Best,
R o s s
Ross S. Stein U.S. Geological Survey, MS 977 345 Middlefield Road, Menlo Park, CA 94025 Tel: 1 650 329 4840 Fax: 1 650 329 5143
