Dear Azadeh Amiri,

here: http://ngawest2.berkeley.edu

you can access the PEER ground motion database and find relative information. 

Regards,

Gabriele

I think your question is not clear. Perhaps you want to know whether the sensor that recorded the data has been installed on soil or bedrock as soil is likely to amplify the PGA. Your question may have arisen from a belief that the earth's surface is always underlain by soil and the bedrock is always found at depth. Even at the earth's surface one finds the bedrocks exposed, and the seismologists always prefer to install the seismic sensors on bedrocks. It is safe to assume that a given seismic record very likely  comes from a sensor installed on bedrock. Depending on the geology of individual site, the bedrock may be exposed at the surface or the sensor may have been installed in an adit/tunnel or in a bore-hole drilled into the bedrock. Perhaps the metadata for each site might indicate where the sensor is lying.

Hi Dear Azadeh Amiri

i thinke the Earthquake Records are about surface

also you can choose  type of soil and give amplified earthquake records

must accelerogram  located at surface of ground 

Best Regards

Alireza

Dear Alireza Jafari

Thank you so much for your kind response.

I think the Earthquake Records are about surface,too.but do you have any experience about changing it to bedrock record?

any help will be appreciated

Regards,

Azadeh

Dear L. R. K. Perera

Thanks a lot about your helpful description.

yes,I want to know whether the sensor that recorded the data has been installed on soil or bedrock in the PEERs record data,exactly!!

I'm using the PEER's data, so I'll want to know about PEER's assumption for recording earthquake data.

Sincerely,

Azade

Hello Gabriele Ameri

Thanks for your suggestion, but I know about this site, my problem exactly is about the data that exist, and I want to know whether the sensor that recorded the data has been installed on soil or bedrock in the PEERs record data.

Sincerely,

Azadeh

 some way that you can  solve your problem:

1-use related software to change the records that i don'i know about them

2- use transfer function (in frequency domain) in MATLAB  and apply deamplification factor ( from Transfer function) to the record; this way is very difficult 

3- use the data of table (  page 141 attached file) and change your PGA to underground PGA , then Scale your record with decreasing  Ratio - this way  be inaccurate for your problem 

Best Regards

Alireza

Hello Alireza

Thanks alot for your very helpful file.

I'll hope the best for you,

Azadeh

Ms Amiri,

Your question is ambiguous. If by bedrock you mean downhole stations in rock, then none of the PEER records are downhole, all sensors are at the surface. But some can be considered rock.

One of the many columns of the published NGA-West2 excel flatfile (which can be found along with the report here: http://peer.berkeley.edu/ngawest2/databases/) gives you the Vs30 (m/s). Sorting by that column will let you choose sites that you consider as rock. If you want hard rock, then most records will likely be too soft (California rock is often taken to have a Vs30 of 750 m/s or so).

Before you start deconvolving records from soil to rock (for which there are many techniques, as mentioned above, but also more uncertainty, thus they should be applied with care), be aware that PEER does not only have a flatfile for NGA-West2, but also one for NGA-East, which was recently completed. This pertains to the Eastern North America region, and will contain more rock data than the West. E.g., it contains records from Canada, where very hard rock sites exist (by sorting by Vs30, you'll find quite a few sites with 2000 m/s). Here's a link to the database: http://peer.berkeley.edu/publications/peer_reports/reports_2014/webPEER-2014-17-NGAEast-Database.pdf, and for the flatfile you would go to appendix C. I believe that right now only PSA values are available, but soon they should also give time histories. 

Regards,

Olga

Dear Olga-Joan Ktenidou

Thanks for your comprehensive description.

What do you mean about surface in this sentence "all sensors are at the surface" ?surface of soil or bedrock?

I'm modeling the soil and I want to apply the earthquake to bedrock.at the other hand I access just the PEER's data.so I want to know about this fact that if these data are surface record so I should chang it to bedrock one,then apply to my model.

Am I right???

I await your response in kind...

Best appreciation,

Azadeh

Azadeh,

It would depend on what you mean by 'bedrock'. As I said, there is great range of site conditions across the (surface) stations in the NGA databases. Vs30 values in the flatfiles should give you an indication.

I do not know the aim of your study, but if you want to propagate rock input motions through soil profiles to compute surface response, and if you're not experienced with site response and/or deconvolution, then I suggest also trying to work with some database that has couples of surface and downhole stations. E.g. in Kiknet you have simultaneous records at the top and bottom of several boreholes, and the profile. By using the downhole bedrock records as input, and propagating through the known soil profile, you can attempt a blind prediction of the surface motion and then compare with the observed surface records. 

Also, if you're looking in NGA for rock records in order to use them as engineering input motions at the base of some numerical model, then may I suggest taking care with both the scaling of the motions as to PGA, and with the surface doubling effect. 

Hope this is of some help. Good luck with your study.

Olga

Hi Dear Olga

Thank you so much for your very helpful description.

All the best,

Azadeh

You may check the earthquake catalogue in the SHAKE2000 software, you can fine all possible information there.

Thank you

Thanks Abhishek Kumar for your response

Seismic hazards during many disastrous earthquakes are observed to be aggravating at the sites with the soft soil deposits due to amplification of ground motion. The characteristics of strong ground motion, the site category, depth of the soil column, type of rock strata, and the dynamic soil properties at a particular site significantly influence the free field motion during an earthquake. In this paper, free field surface motion is evaluated via seismic site response analysis that involves the propagation of earthquake ground motions from the bedrock through the overlying soil layers to the ground surface. These analyses are carried out for multiple near-fault seismic ground motions at 142 locations in Mumbai city categorized into different site classes. The free field surface motion is quantified in terms of amplification ratio, spectral relative velocity, and spectral acceleration. Seismic site coefficients at different time periods are also evaluated for each site category due to near-fault ground motions from the acceleration response spectra of free field surface motion at each site and the corresponding acceleration response spectra at a reference rock outcrop site.

Seismic hazards during many disastrous earthquakes are observed to be aggravating at the sites with the soft soil deposits due to amplification of ground motion. The characteristics of strong ground motion, the site category, depth of the soil column, type of rock strata, and the dynamic soil properties at a particular site significantly influence the free field motion during an earthquake. In this paper, free field surface motion is evaluated via seismic site response analysis that involves the propagation of earthquake ground motions from the bedrock through the overlying soil layers to the ground surface. These analyses are carried out for multiple near-fault seismic ground motions at 142 locations in Mumbai city categorized into different site classes. The free field surface motion is quantified in terms of amplification ratio, spectral relative velocity, and spectral acceleration. Seismic site coefficients at different time periods are also evaluated for each site category due to near-fault ground motions from the acceleration response spectra of free field surface motion at each site and the corresponding acceleration response spectra at a reference rock outcrop site.

Hello Mr Ali Saidul

Thanks for your response.

Sincerely,

Azadeh