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Seismic Hazard - Science topic

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Let's say some truths that we hide under the carpet, but come to the surface after every big earthquake. Do the newly built structures withstand the earthquake? Yes, they can withstand the seismic acceleration of design. The Greek area is divided into three seismic hazard zones. The values ​​of design ground accelerations are 0.16g (percentage of gravity acceleration g) for the first zone, 0.24g for the second zone and 0.36g for the third zone. Yes, they can withstand these earthquake accelerations. However, historically earthquakes of the order of 1 g have been recorded in Greece with much greater territorial acceleration. What happens to these earthquakes that are greater than the design acceleration? The largest earthquake in the world had an acceleration of 2.9 g At these accelerations, the constructions have absolutely no luck That's why you need my patent. There are also projects of extreme importance such as nuclear power plants, hospitals, schools. In these projects, how do we prevent disaster?
The purpose of the modern seismic regulation is to construct structures that: a) In frequent earthquakes most likely to happen nothing will happen, b) In earthquakes of medium probability to occur will suffer small, repairable damage and c) In very strong earthquakes of low probability to occur we will have no loss of human life. So we should not use the term "absolutely" in seismic constructions. We should use the term "quality" constructions which means application of at least the requirements of all modern regulations. The quality of constructions and their safety is also a function of the economic situation of the countries, among other factors. It is understandable that poor countries cannot be compared to countries where they have strict modern seismic regulations. Conclusion… there is no absolute seismic design today, and we should not refer to absolute seismic design. So there is a great need today to invent a more modern anti-seismic design that meets the ultimate anti-seismic design, with lower construction costs.
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I do not think so
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How to develop a limit state equation ( in terms of capacity and demand) for bridge components such as deck, pier, and foundation in the event of a seismic hazard. My goal is to evaluate the reliability associated with it utilizing various reliability approaches. I can do it with fragility analysis or even modelling, but I'm looking for an equation that I can use to numerically measure reliability. Can someone recommend some research papers or any book anything related to the same?
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"AASHTO Guide Specifications for LRFD Seismic Bridge Design" presents analytical formulae for resistance and load, in the context of seismic design. Those should help you define your performance function. You can download the text on : https://za1lib.org/book/2359958/0f6b56
All the best
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Do you admit that there must be a seismic culture among inhabitants and individuals to manage seismic risk?
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I agree with you Amira. It would great if we could conceive what would be a seismic culture.
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The purpose of earthquake engineering is not to build strong and earthquake-resistant buildings that do not experience the slightest damage in rare and severe earthquakes. The cost of such structures for the vast majority of users will have no economic justification.
Instead, engineers focus on buildings that resist earthquakes' effects and do not collapse, even in severe external excitations. It is the most important goal of international standards in the seismic design of buildings.
Below I have mentioned some crucial points in reducing the seismic demand in reinforced concrete structures. If there is anything else that is not on the list, feel free to append:
1- Selecting suitable construction conditions with the desired soil type of seismic design
2. Avoid using unnecessary masses in the building
3- Using simple structural elements with minimal torsional effects
4. Avoid sudden changes in strength and stiffness in building height
5. Prevent the formation of soft-story
6. Provide sufficient lateral restraint to control drift through shear walls
7- Preventing disturbance in the lateral behavior of the structure by non-structural components
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Applied an equivalent horizontal force acting on each floor according to seismic zone.. also mode a numerical excitation in many cases shows a dynamic load factor (1.5 to 2) or higher!
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For instance, while comparing the response spectrum curve in IS 1893-2002 with that of ATC-40, Ca = Z/2 and Cv is either of Z/2, 1.36·Z/2 and 1.67·Z/2 for hard, medium and soft soils respectively for DBE.
While doing the pushover analysis using capacity spectrum method (ATC 40), what would be the values for Ca and Cv with respect to the response spectrum curve given in NBC 105:1994???
As the values are expressed in terms of coefficients, it's rather confusing to figure out the value of intensity of ground acceleration.
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I agree with the statement of DR. Karim
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Dear researchers
Risk-Adjusted Maximum Considered Earthquake (MCER) Ground Motion, which considers structural collapse risk of each site in seismic hazard analyses, is used to prepare seismic hazard maps provided in United State Geologic Survey 2010 (USGS 2010).
The mentioned collapse risk are considered in MCER through risk coefficients and applying to Maximum Considered Earthquake Geometric Mean (MCEG).
How these coefficients are calculated and applied to seismic hazard maps?
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Dear Majid,
The answer to your question is very long. You will find your answer in the following papers.
- Risk-targeted versus current seismic design maps for the conterminous United States (Luco et al. 2007)
- Risk-targeted seismic design maps for mainland France (Douglas et al. 2003)
Let me know if you need more information.
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Open source and easy to learn with proper documentation.
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Thank you sir. It is very useful !! S.M. Talha Qadri
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Hi Everyone
I am using R-CRISIS for seismic hazard map creation. I know how to use the given attenuation model in R-CRISIS but I want to use an attenuation model from a published article. How to make such an input file? Also, I would like to know, how to find out suitable spectral ordinate parameters for each zone for R-CRISIS? (It will be so helpful if you explain the later one in detail)
Hope Somebody can help me with this.
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About your first question :
You have to create a text file according to the desired attenuation model and change the format of this text file from txt to ATN. Then, you should import the defined text file through R-CRISIS ( attenuation data>add user model) and then you have to assign this attenuation model to the desired seismic source. It should be noted that this method is for CRISIS2007 which is also applicable for R-CRISIS.
The mentioned text file should be look like the attached file. I think that Kramer's book explains how to make this text file. I have attached a manual which is in Persian.
About your second question:
The hazard curves often obtain based on Peak Ground Acceleration (PGA) and also most attenuation models are based on this spectral parameter.
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I went through FEMA-356 and FEMA-440 for target displacement and I cam across the formula as well but it wasn't helpful as i'm not able to understand it completely and I wasn't able to find all of the coefficients. It would be great if i can get a solution for that.
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You can use SeismoStruct software for the calculation target displacement based on ASCE41-17.
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Is there a way or a simple code / software that can eliminate aftershocks of a main event with respect to time and distance?
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Dear Redouane,
There is no sure-fire way to way to "automatically" decluster earthquake catalogues! Methods of declustering have evolved from the generally inefficient deterministic (e.g. Gardner and Knopoff, 1974; Reasenberg, 1985) to the more complicated stochastic (e.g. Zhuang et al., 2002; Marsan and Lengliné, 2008). An excellent review is provided by van Stiphout et al, (2012). The former identify aftershocks using temporal and spatial windows that usually depend on the main shock magnitude while ignoring aftershocks of aftershocks (higher order events). The latter allow for aftershock triggering within a cluster and use Omori’s law as a measure of the temporal dependence of aftershock activity. Both approaches ignore fault elongation for larger magnitude events, assuming circular (isotropic) spatial windows. Stochastic declustering was pioneered by Zhuang et al. (2002) and is based on space-time branching techniques to describe how each event triggers its successors. Nevertheless, it is parametric (model driven). It improves on previous methods in that the choice of space-time distance is optimized by fitting an ETAS model to the earthquake data. Moreover, instead of associating an aftershock with one main shock, each earthquake is assigned with a probability that it is an aftershock of its predecessor. This means that all earthquakes are possible main shocks to their short-term aftermath and neatly circumvents the problem of having to make committing binary decisions in the frequent cases of nearly equal space-time distances between successive events. Marsan and Lengliné (2008) carried stochastic declustering one step forward by introducing a generalized triggering process without a specific underlying earthquake occurrence model, although they still assume that background earthquakes occur at constant and spatially uniform rate density.
So there you have it... simple way there is not! Better use stochastic methods, although they require significant effort to understand, and depending on the quality of the catalogue hope for the best...
References
1. Gardner, J. K., and Knopoff, L., 1974. Is the sequence of earthquakes in Southern California, with aftershocks removed, Poissonian? Bull. Seism. Soc. Am., 64 (5), 1363-1367.
2. Reasenberg, P. 1985. Second-order moment of central California seismicity, 1969-82, J. Geophys. Res., 90, 5479, 5495.
3. Marsan, D. and Lengliné, O., 2008. Extending earthquakes’s reach through cascading, Science, 319, 1076; doi: 10.1126/science.1148783.
4. van Stiphout, T., Zhuang J, and Marsan D., 2012, Seismicity declustering, Community Online Resource for Statistical Seismicity Analysis, doi: 10.5078/corssa-52382934. Available at http://www.corssa.org.
5. Zhuang J., Ogata Y. and Vere-Jones D., 2002. Stochastic declustering of space-time earthquake occurrences, J. Amer. Stat. Assoc., 97, 369-380.
6. Zhuang J., Ogata Y. and Vere-Jones D., 2004. Analyzing earthquake clustering features by using stochastic reconstruction, J. Geophys. Res., 109 (B5), B05301; doi: 10.1029/2003JB002879.
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I need to asses what would be the consequences of earthquakes over a cylindrical water tank embedded in soil (roof is at the surface of the soil).
I was wondering to do a spectral response analysis but does this makes sense if the whole structure is below the surface?
What analysis can I do over the structure to asses seismic risk? Any recommendation is appreciated!
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In general the answer of your question is yes and I explain more below about the conditions and applications to do a spectral response analysis for a water tank when it is supposed to be embedded in the soil. In water tanks embedded in soil, at least to some extent, for many cases, the conditions of embedment are complicated. For example, structures are not supported uniformly around their circumferences because of adjacent structures and cuts in the soil, such as for the connected pipes, etc. Water embedment has a significant effect on soil-structure interaction: in comparison with a surface foundation, both the water tank input motion and the water tank impedances change for an embedded water tank. For vertically propagating waves, a horizontal shear wave produces both a horizontal translation and rotation of the embedded massless foundation; a vertical compression wave produces a vertical translation and rocking of the embedded massless water tank. In general, the amplitude of a water tank input motion for embedded water tanks is less than that for surface water tanks, especially in the high-frequency range. Structural responses are thus reduced for embedded water tanks. For water tanks, during the seismic design of a soil-foundation-structure system, if the water tank is embedded under the soil surface, design response spectra at the control point under the soil surface. However, location of the water tank is not always known at the time when the design response spectrum is constructed. Thus, design response spectra at several depths of the site profile need to be established considering the free-field ground response; the effect of soil-structure interaction is not considered. Besides, because soil parameters usually exhibit large variabilities, it causes uncertainty of the design response spectra at various depths of the site profile. Thus, probabilistic design response spectrum at a control point under the soil surface may be required to accurately reflect the seismic hazards at corresponding locations.
I hope my answer is helpful and responded to your question.
Best of luck.
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Based on landslide scaling relationship, we observed that a transition zone exists in the NW Himalaya that differentiates the landslide volume capacity of the hillslopes and possibly landslide frequency.
The most probable reason could be spatial variability of the Indian Summer Monsoon that depletes in the Indian Himalaya in a ESE-NW direction. The other potential reason could be seismic activity. My question seeks the explanation in seismic context.
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Thank you R. Arun Prasath .
I will read these articles and will let you know for further, if any, query.
Thank You.
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Building exhibit torsional rotation under seismic loading due distance between the center of mass and center of rigidity. According to building codes, does this distance or torsional rotation have any limitations? And if not, how could I check the capacity of building for large torsional rotation?
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Thank you so much Denniis Miller
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During earthquake,what mimimum value of Surface PGA can be expected to cause damage to any poorly constructed building in India?
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Dear Zinat,
Thanks for suggesting the paper by Prof. Jain, However, it does not mention anywhere the about the minimum value of Surface PGA can be expected to cause damage to any poorly constructed building in India. In general, a PGA value of about 0.05g is considered good enough to cause damage to poorly constructed buildings in India. However, please note that PGA is not the only parameter for damage but there are several other parameters which are important from damage perspectives, such as strong motion duration, building natural period/ frequency as well amplitude of ground motion at or close to the building natural frequency.
Hope, this answers Rafiq question.
Thanks
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Valid answers with reference needed.
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See we build structures on the surface, so why we need the effect of deep soil.
The deep geology mostly transfer the energy to the layers of soil foundation which our structures lay on.
The surface layers only deformed under the seismic load as well as our infrastructures.
We need to know the properties of the first 30 m as many antiseismic design codes suggest.
Deep soil only increase the total vibration time but not the peak ground acceleration. The deformation of the huge thickness of unconsolidated soil appear on the top.
Considering deep soil in our PGA will lead to lower value of design PGA.
The deep soil can attenuate the energy of seismic wave due to water saturation and other factors.
Knowing the soil predomenant frequency will help to avoid high design acceleration as well as resonance occurreance.
All the best
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Good morning everyone;
I have a synthetic PGV values for my study area, that I generated only for rock soils, I was wondering if there is a way to apply some perturbations on my results in order to reflect the basin's effect or the shallowest layers.
I do have a Vs30 map of my study area. Is there a link between Vs30 and the PGV that allows me to tell how far the PGV can amplify (or not) according the Vs30 values.
Thank you very much.
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You would can do this yourself. Using Experimental observations lead to a relation but just for area of your study.
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Historic earthen structures are a significant part of the built heritage worldwide and are associated with intangible building techniques, wide material availability and low cost construction. Nonetheless, due to their low mechanical properties and, often, poor connections, historic earthen structures are susceptible to early structural damage and even collapse in areas of high seismic hazard. InIn additionthe lack of maintenance can further reduce structural performance and durability.
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The PGV to PGA ratio is known as a significant parameter for the damage assessment of structures under earthquake shakings. As a matter of fact, it is considered as a descriptor of the frequency contents of the seismic input motion. I am interested in understanding the physical and seismological significance of that ratio, and finally the engineering meaning, and its correlation with the structural damage.
I could not find technical treatments except empirical measurements.
Many thanks in advance for your contribution.
danilo
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Consider a SHM for which displacement y = Acos(wt+B), Then velocity v = -wAsin (wt+B) and acceleration = -Aw2cos(wt+B). Thus the ratio PGV/PGA = 1/w i.e. the inverse of the circular frequency = 1/(2πf) = T/(2π ).
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I use Atkinson and Boore (2011), Chiou andd Yaungs (2008), Campbell and Bozorgnia (2008) eauations for seismic hazard assessment.
some parameters at these equations like type of faulting, dip angle, rupture width, depth to top of rupture... are identified for linears sources, however, sources of my zone are area sources.
would you please let me know how to use those parameters for area sources using attenuation equations?
does anyone please know to help me?
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The depth of earthquake events are the crucial problem in use an area- source model. Therefore you can estimate the depth with appropriate estimation. The other parameters you can input directly to the ground motion prediction equation that you use
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The design response spectrum provides a general procedure to estimate the expected dynamic load on a structure which is expressed as a function of natural period. Thus knowing the period of the structure, design load could be calculated. It well known that the deterministic (DSHA) and probabilistic (PSHA) seismic hazard maps provide prediction of peak ground acceleration and ground motions for a specific site. As per NEHRP guidelines, design response spectrum is developed from the PSHA framework. The 2% pr 10% probability hazard level can be used for development of design response spectra which is actually satisfying a MCE level condition.
The accuracy in determination of PSA is very important in calculating the final shear load. Could you explain how to estimate such value for a given site?
How to calculate spectral acceleration (design acceleration) for the each type of site class?.
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Read section 11.4 of ASCE 07-10. It is explained there clearly.
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In statistical and probabilty anslyses we are asked to compute error and uncertainty curves and values. 
Do you think there are absolute fixed error or uncertainty? Do we reach the time to say what error exist in our answers?
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Dear Dr. Raed Ahmed,
The following article may be of your help.
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Recently, there are many earthquake cluster (if can be called) or earthquake sequence happened in a short time and at a same place. I have used the ETAS (only time analysis) model study the characteristic of the sequence, but the result is not good to give a complete decision. So i ask some advice to you who study this problem or some scientist major in time data analysis. If you have any good advice or have known some better analysis tools, please let me know or sent me a message directly. Thank you!
yours
zhang
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Not very sure of your requirement. Nevertheless; earthquake clusters are mainly of two types: 1) Foreshock-Mainshock-Aftershock (FMA) or MA sequence and 2) earthquake swarm. Both form spatio-temporal cluster. For seismic hazard study (DSHA or PSHA) FMA or MA cluster, it has to be de-clustered first and then further study. 
For statistical analysis whether a seemingly cluster is significant or not, there are various published papers. Check our paper 'Potential Source zones for Himalayan earthquakes: constraints from spatial-temporal clusters'. Nat Haz 2011, 57, 369-383 available in RG. Several other papers on seismic clusters by our group can be consulted all available in RG.
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As we know, there are many software for 1D site response analysis, namely SHAKE, DEEPSOIL...
Now, I need a software for 3D site response analysis. Is there any commercial software for 3D analysis of basin response to ground motion?
Can we use ANSYS or ABAQUS or PLAXIS for 3D analysis of basin response to long-period ground motion?
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hy,I would like to know how to enter the parameters of deepsoil to plaxis?
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Is Main central Thrust (MCT) or Main Boundary Thrust (MBT) active or both are active in Bhutan Himalayan region?What is the impact of these two thrusts on nearby hydropower projects or other construction projects?Is it related with the failure of rockbolts of the powerhouse of Tala Hydropower plant?
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All thrust faults (MCT/MBT/MFT etc) within the Himalayan domain are seismically active, though not uniformly along and across Himalaya. All the thrusts are emergent faults from the Main Himalayan Thrust (MHT). Major earthquakes (>= 7.0) originate from MHT and rupture can propagate up dip; in some cases fresh rupture can continue to break the surface along either of these emergent thrusts ( e.g., 2005 Kashmir earthquake) or as new surface rupture (note that the 2015 Nepal earthquake didn't produce surface rupture).
Many HEP are located at or near these faults in the Himalaya. Site specific seismic design parameters (Through PSHA/ DSHA) are considered so that the built structure can withstand the expected acceleration due to seismic shaking during an earthquake.
Having said so one has to take care of the situation that structures are not sited on/close to active faults/ shear zones. In case of surface rupture where structure is located over/near it, no amount to seismic design can help. Check what happened to a dam at Taiwan during the 1999 Chi-Chi earthquake. Other than direct rupture during earthquake, structures can undergo distress during inter-seismic periods due to strain localisation along weak zones through tilting/warping/folding etc.
With this information hope the situation at Tala HEP can be better appreciated...
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Hello 
Hope everything is going well. I need help. I prepared seismic source zonation map of my country. Now I want to prepare seismic hazard map using zonation. Can you provide me any code and manual to prepare such map? It will be very much helpful for me. Thank you. 
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I agree with all above replies. But i suggest you to answer the following questions which may help you in your study.
Will you calculate PGA or PSA? 
What is the attenuation model that you intended to use?
Will you use you Logic tree concept or not?
Do you think your previous seismic hazard maps succeeded to predict earthquakes?
Do you have a full trustable and homogeneous seismicity catalog that allow to calculate your seismicity parameters?
Regards
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I want to investigate the linear as well as non-linear responses of earthquake events, regarding this is there any other available tools such as NERA and EARA.
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Dear Nilutpal Bora
You can visit the link below, the programs were made by Prof. Nozomu Yoshida, Tohoku Gakuin University. All Softwares are free.
Here, the list of the programs:
-DYNEQ: Equivalent linear earthquake response analysis of ground
-YUSAYUSA: One dimensional seismic response analysis of ground based on effective stress 
DYNES3D: Truly nonlinear one dimensional seismic response analysis of ground with three directional input
DYNEQ is similar to SHAKE, NERA, and EERA. Detail can be found in the link.
Hope this help.
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The earthquake occurrence is more complicated than the models on which hazard maps are based. Hazard maps often depend on poorly constrained parameters, whose values are chosen based on the mapmakers' preconceptions. When these are incorrect, maps do poorly.
What to do to improve seismic hazard maps?
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Dear Ahmad,
The irreducible random uncertainties  often didn't affect the reliability of seismic hazard results. What is affecting the reliability is the scientific uncertainties (state of earth sciences knowledge which it was the case even in Japan (Tohoko) 2011.
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I would like to estimate Vs30 for seismic hazard assessment in the NW Himalaya using proxies some like Geo morphology or Topographic slope complementary with strong motion data in that region. This is part of my PhD work, kindly suggest me. I would very thankful to you.
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 Thanks, Hansen & Chaudhuri for your kind information.
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In regard with the Attenuation Relationship for Seismic Hazard Analysis, with scenario below:
Site selection for seismic hazard: located on stable continent.
Source zones: At subduction zone approximately 500++km away from the site.
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Which attenuation relationship that is suitable to be used for seismic hazard analysis on stable continent with sources from subduction zone/shallow crustal zone?
I tried different Attenuation Relationship which derived for stable continent, subduction zone and shallow earthquake and get a different result but not exactly sure which relationship that represent the best with the above scenario.
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There are some attenuation relationships in the case of Subduction fields, Like ........., which u can use them in SHA. Mainly they presented by PEER and USGS and NGA. By searching this references you can find your interest relationships. also Francesco left a link in which many relationships (but in short description) that you can find your desired relationship.
Good Luck
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I’m planning to investigate damage increasing of concrete frame structures subjected to seismic sequence.
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This depends upon the structure. For a simple SDOF (single-degree-of-freedom) oscillator, the yield displacement is simply the yield strength divided by the initial stiffness. The displacement ductility demand (to distinguish from the curvature ductility demand - they are very different) is then simply the maximum displacement divided by the yield displacement, and is different for each ground motion analysis (the yield displacement is not). For a MDOF, there is, strictly speaking, a displacement ductility demand on every member of the structure. The largest may or may not be the most critical. A well designed column might have a displacement ductility capacity of 6, while a poorly detailed column might have a displacement ductility capacity of 3.
It is possible to convert an MDOF into an equivalent SDOT in some cases. See:
Priestley, M.J.N. and Mervin Kowalsky, "Direct Displacement-Based Seismic Design of Concrete Buildings", Bulletin of the New Zealand Society for Earthquake Engineering, 33(4), December 2000, for example. Best of luck in your work.
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I have to identify the region where seismic activity occur within a depth of 200m and estimate the seismic hazard in and around a closed mining area.
How many minimum geophone stations are required for the estimation of seismic hazard in an area of 5Km by 2Km?Are five number of triaxial geophones sufficient for this?
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Hello Pierre,
My objective is to identify the regions where seismic activities occur within a depth of 200m which would affect the dwellings and estimate the seimic hazard in the closed mining area.Will five geophone sufficient for these two objectives?
Kind regards
Vikalp Kumar
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There are several things which can cause the formation of earth vibrations initially; I wish to know in detail.
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The following natural or induced processes can generate earthquakes.
(1) Tectonic (2) Triggered (reservoir; fracking) (3) Volcanic (4) Mining (5) Oceanic microseisms
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Neo Deterministic Seismic Hazard (NDSHA) is compared to PSHA asserting that the latter overestimates observed PGA values for medium-weak earthquakes (Italy case) and, more seriously, PSHA does not provide preventive values for large earthquakes (underestimation of PGA values). I am interested in a comment or opinion from both engineers and seismologists.
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Hypothetically calculating the impact of a co-seismic landslide on a railway bridge we have: (the probability of the earthquake multiplied by the models epistemic uncertainty multiplied by the probability of a landslide multiplied by its associated epistemic and aleatoric uncertainties. Are the latter two uncertainties dealt with as separate entities or should they be combined before running the entire equation?
So should it be Peq X Peqepi X Pls X Plsepi X Plsale = Hazard exposure
or
Peq x Peqepi x Pls x (Plsepi x Plsale) = Hazard exposure
where Peq = prob earthquake, PZepi is PZ epistemic uncertainy & PZale = aleatoric uncertainty
Furthermore should the aleatoric uncertainty be a larger decimal or a smaller one for seismic hazard as this will impact the model severly? ie 0.9 or 0.1.
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This is a good question. In geohazards, aleatoric and epistemic uncertainties are difficult to distinguish. Separation of these two uncertainties is arbitrary, even like "splitting a hair."
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In Building code, there is only response spectrum for short to medium period (<1s) for site A,B,C,D,E.
In case of deep soil basin (Osaka, Kanto, Los Angeles... basins), the predominant period may be up to several seconds. It is very dangerous for high-rise buildings in these regions if there is a large earthquake which releases long-period energies.
How is the design response spectrum? Is it mentioned in any code or document?
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In my opinion, the top soil layers generally govern the response of site. While developing the design response spectrum, it is generally assumed that deep soil profiles produce similar response to soil profiles whose depth is 30m. Hence, they have a cut-off at 30 m depth, which seems practical as site investigations do not generally proceed to deeper depths. If you want to design a very tall structure then I would suggest you perform site specific response analysis. One thing make sure to include long period earthquake for your analysis.
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We all work around Seismic Risk. Structural Behaviour, Retrofit Techniques, Scenario Simulation, Loss Quantification and so on. But. Do people feel at Risk? If not, how can citizens be willing to pay Seismic Risk Reduction policies and practices? Do people know about Feasible Risk Reduction Strategies and actions? If not, how can people be willing to pay Seismic Risk Reduction policies and practices. If someone has any ideas about this, please share.
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The real problem, as previously claimed by Max Wyss, is how to reach the population or better how to engage the society in the risk reduction and the connected actions. Probably the better choice to reach the claimed objective is to orient our action towards the risk acceptance.
The risk perception not includes necessarily a responsability assumption, the acceptance yes.
Even though the perception implies cognitive aspects of the risk, it has more psycological implications than the acceptance, which, differently in my opinion, implies a real taking in charge of a comportamental choice (social in latu sensu).
The risk acceptance is an evaluation of the advantages / disadvantages of some actions (scientific, technical, psycological, social, economical) in order to proceed towards an operative choice finalized to the risk reduction and to the consequent taking of the social-economic risk.
In my opinion the acceptance should include a real engagement of the public which is subject to the risk condition through different level of an information program, oriented to the cognitive and psycological risk perception (risk assessment, risk exposition, modification of the life quality), and mainly finalized to the risk acceptance (responsible decisions and actions in the risk condition)
Probably in this condition, the public could partecipate effectively to a program of risk reduction.
For example a scenario or a simulation, which includes also social and economical effects does not inform the citizen how his life could be modified in terms of his responsabilities and consequent actions. Basically it is useful to furnish important information to the decision/policy makers. But, how much information contained in a scenario or in a simulation are useful for a citizen in order to protect himself and to contribute to the reduction of its real risk? Or best, how the important information contained in them becames useful to enhance the responsibility of a citizen community?
Until the risk reduction programs will be only the result of a top-down process from scientists and/or decision makers and/or legislators to social community, this community will not understand why it is important a politics for risk reduction and why it should take in charge part of the cost (social and economical) connected to its reduction before, during and after an event.
The risk reduction is basically similar to that of a network problem with distributed users over different levels, each level of network contributes to the real risk reduction.
The taking the social-economic risk in distributed form is a factual way to distribute the environmental-risks at each user level through its acceptance of a part of risk (technological-social-economic choices and actions).
A trivial example: when we assure our car we are informed about our part of the assured risk and accept it and the risk taking correspond to a comportamental responsibility and action (the acceptance).
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I have been working in PSHA (Probabilistic seismic hazard analysis) and I could not find information about the Stepp´s method, mentioned in the question, used in the completeness analysis process of seismic catalogs. I will appreciate if someone could help me onto this.
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I would not use Stepp's method, I would use the ZMAP program of Stefan Wiemer that has several methods coded
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3D-1D broadband simulations of ground motion are normally performed by using a hybrid approach where full wave numerical methods are used for the low frequencies and a stochastic contribution has added a posteriori to achieve high frequencies. The cross-over for hybridization is established empirically in a band between about 0.5 Hz and 2 Hz depending on the earthquake magnitude size, distance, local structure and shape of Fourier spectra of low frequency synthetic seismograms.
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Caro Alessandro,
to my knowledge there are no papers that specifically focus on the cross-over frequency between a deterministic and a stochastic modeling. In our paper on hybrid modeling of L'Aquila earthquake ground motions published on JGR (that you can find on my page):
"Complexity of theMw6.3 2009 L’Aquila (central Italy) earthquake: 2. Broadband strong motion modeling"
we discussed about this issue in Section 7. You can find some relevant references there.
I hope you find this of some help.
Ciao
Gabriele
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Seismic hazard estimation
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There is much debate about Mmax. An emerging consensus among seismologists is that Mmax by itself does not have a clear meaning. Sometimes it is interpreted as the largest possible earthquake on a fault, plate boundary segment, or closed region, but there is no reliable method to estimate it because we do not know the physical reason why earthquake rupture stops. Historical + 0.5, and Wells/Coppersmith regression, fail frequently; recorded earthquake commonly exceed the predicted "Mmax". A more reasonable statement can be based on the time period of interest. Given a clear definition of the area of interest (e.g., closed polygon), an earthquake catalog and fault information can be compiled and the magnitude frequency relationship can be estimated. This can be extrapolated to the time period of interest, and a statistical estimate of the probability of occurrence of any given magnitude can be computed. Clearly this method, like all others, fails if the time period of interest is infinity. For very long but finite time periods, it may be appropriate to assume a magnitude distribution with a "maximum considered magnitude" or a "corner magnitude" . The predicted long-term seismic moment rate then depends on that parameter, and adjusting it to fit the long term tectonic moment rate (from plate velocities, fault slip rates, or geodetic observations) can provide an estimate. Such estimates must be considered as statical estimates, not as a strict limit to the possible magnitude. For more info, check out
Kagan, Y. Y. and Jackson, D. D., 2013. Tohoku earthquake: a surprise? Bull. Seismol. Soc. Amer., 103(2B), 1181-1194, doi: 10.1785/0120120110, and references within.
Bottom line: start with a clear definition of the region and time period of interest first, then use available data to infer frequency vs. magnitude.
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Soft storey/weak storey effects
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According to seismic provisions in ASCE 7-10 and MSJC-13, if masonry partitions are seismically isolated (lateral and top joints), partitions are considered non-participating to building seismic resistant system. Otherwise, they should be considered as participating walls. And, they should designed accordingly.
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For micro seismic zonation, lateral variation in the P-wave velocity is an important parameter because the unconsolidated zones having lower velocities are supposed to have higher amplitude response during the earthquakes. Sometimes, for shallow subsurface investigations, procuring equipments for seismic surveys prove to be cost prohibitive. However, electrical resistivity is a much cheaper means to investigate shallow subsurface stratigraphy. The problem is can we compare the velocity information with resistivity?
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Dear Siddhartha, I think there's some confusion here... Changes in "density, lithology, material composition, porosity, saturation, and compaction level" affect both the seismic velocities and resistivity. Unfortunately, they do not affect them in he same measurable manner, because seismic waves convey the response of the Earth to changes in the stress field and electric or electromagnetic fields convey the response to changes in electrical conductivity. Sometimes these changes coincide and you can use conventional geophysical techniques to locate interfaces (including inversion). In most cases they do not, or they tend to get blurred by collateral effects, as for instance capillary infiltration in porous sediments, scattering and other such nasties. Moreover, seismic and electrical methods are incomparable in terms of resolution. In general, calibration in the form of simple (e.g. linear) models is not feasible and you need observational redundancy (e.g. in the form of multi-parametric measurements). Also forget all about estimating seismic velocities on the basis of conventional resistivity measurements. The best way to be sure about the coincidence of seismic and electrical interfaces, if there's underground water, is to use geophysical methods that record a COMMON responses from such interfaces - for instance, have you ever considered the seismo-electric conversion? Unfortunately this requires seismic equipment...
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There are tons of techniques to do that. As suggested by Ivan dealing with soil layers is among alternatives. Going up we reach to Arman's comment which,as far as I understood, indirectly referred to base isolation. Go upper through the stories you can use different kinds of dampers and when you reach to the roof, you would find it a good place for putting some vibration absorbers such as TLCD, or TMD.
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I know openSHA allows to select deterministic or probabilistic approach, but their open source Java code does not reveal much of deterministic approach. I want to know if any other software is available.
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I recommend mHARP.
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Since most of the popular methods are developed with US/European data.
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Thank a lot....We are following almost the same procedure in Bangladesh,,,,:)
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We are investigating Volcano Monitoring using WSN, we actually need to adapt geophones to our wireless network and we need to buy some of them, or maybe there is an institution interested in participating as a sponsor.
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The sensor is sensitive to wide frequency range in excess of 100Hz. You can use a filter to restrict to 50Hz or below.
Yes, I can help you build the sensor front-end electronics or even we can think of some joint activity.