Perhaps the plot attached can you help.

M.

Unfortunately I do not have actual site data/ Plot in any form . I need to select a sensor that is suitable for earthquake vibrations monitoring, and as I came to know : the frequencies above 500Hz are more significant with respect to earthquake, and those which are less than 500Hz are ignorable sincce they dont cause any damage.. I need to validate this fact, and also want to know correlation of "Freq. Range" with the "Richter scale " or with respect to "g" . Kindly help...

Hi Amol,

I'm not a seismologist but I am interested in earthquakes. I could Google this, but so could you. I'm pretty sure you are very far off on saying frequencies above 500 Hz are more significant. I think frequencies of more like 1 Hz are the problem for taller buildings: closer to resonant frequencies of such buildings. I doubt 500 Hz does almost anything to any building. Please check and repost here: I'm curious whether I am correct.

Also, there need be little correlation between earthquake magnitude and acceleration. You can have accelerations of 1 g for a M6.0 quake, and less than that for a magnitude of 9.0. It is intensity, not magnitude, that is related to accelerations. Accelerations are related to site conditions (soft ground/deep sedimentary basins amplify this) distance, type of quake, direction of rupture propagation, etc etc.

If you are doing this in your work it seems important to read a good textbook.

Chris

No direct relations exists to convert the magnitude directly  to the acceleration or vice-versa. 2g could be recorded both for a M=5.8 or for a M=7.5 earthquake in the near source field. Acceleration is influenced by wave propagation effects, seismic source and local effects at the measuring site. As an example, the Shindo scale in Japan used for intensity meters express a certain level of shaking in m/s2 not directly linked with the earthquake magnitude. 

Magnitude is a quantity related only to the seismic source. You can find prediction equations (GMPE) based on measurements that depending on magnitude scale could determine the acceleration level at some distance within some uncertainty range. However, the acceleration range at a specific distance and for a defined magnitude is extremely variable.

As Chris told you, earthquakes can cause damage to buildings and other structures in the frequency range from 0.2 Hz up to 20 Hz.  

I think that you will find the wikipedia entry best describes the difference between the Richter scale and peak ground acceleration: https://en.wikipedia.org/wiki/Peak_ground_acceleration

Hello Amol,

Be aware also that the Richter scale is a largely obsolete measure of earthquake magnitude (for larger earthquakes), mainly used these days by the general public and journalists who misquote press releases. Thus, on a light-hearted note, check out:    

https://www.geolsoc.org.uk/Geoscientist/Archive/June-2007/Off-the-Scale

Regards

Graham

The Richter magnitude reflects the energy released by a given earthquake. Depending upon the distance to the epicenter the acceleration at a given place will be greater or smaller. There is, as well, a large influence of the ground type at the recording site.

To find the value of acceleration as a function of  magnitude and distance, taking into account the type of gound at the site,  you can follow the paper:

Morales-Esteban, A., Justo, J.L., Martínez Álvarez, y Azañón, J.M. (2012). “Probabilistic method to select calculation accelerograms based on uniform seismic hazard acceleration response spectra”. Soil Dynamics and Earthquake Engineering, ISSN 0267-7261, 43:174-185. DOI: 10.1016/j.soildyn.2012.07.003. 4 citations.

There are other factors that influence the acceleration from a given magnitude, as it is the whole geology between the epicenter and the site. But this factor is too complex to be taken into account.

I read the Wikipedia article suggested by Jac Fought. It´s very interesting and it has a large correlation table of several earthquake parameters that might be useful to plot to see if there´s a trend between g and magnitude. Let us know, Amol. Cheers!

Dear Amol,

to complete my previous post I suggest to you not loosing time to find correlations between local magnitude and OEM (piezoelectric accelerometers for shock applications) accelerations. There are a lot of papers published all around the world where it's clear that you cannot define a local magnitude from a value of peak ground acceleration.

The Gutenberg-Richter scale is calibrated 1) for velocity ground motion not acceleration and 2) a specific instrument the Wood-Anderson sensor. With the modern professional digital accelerometers (high-cost) you could detect the ground motion acceleration as a full triaxial time waveform on a wide frequency range (from 10s to 0.01s).

By integrating recorded complete seismic waveforms you could easily retrieve velocity waveforms and by convolving them with the Wood Anderson seismic response finally you could define the local magnitude. These processing steps cannot be applied to low-cost OEM. 

Richter magnitude is related to maximum recorded amplitude of surface wave which can be acceleration (in g unit or other units) or velocity.

The most important frequencies for civil engineer when designing infrastructure are 1, 3, and 5 hz (1s, 0.3s, and 0.2s periods).

Seismologists focus on frequency range 0.1 - 100 hz.

Since, Civil engineers are also making taller structures to the order of 100 storey high buildings, so frequencies of even 0.1 Hz is also important. Thus, frequency range for buildings are from about 0.1 Hz to 10 Hz for civil engineers. Seismologist focus on different frequency ranges depending upon what they are interested in - from Earth's Core to Surface waves.

I think that you will find the difference between the Richter scale and peak ground acceleration on website : https://en.wikipedia.org/wiki/Peak_ground_acceleration

Amol Joglekar hi

There is no relation between Richter scale and accleration (g). Richter scale measures the magnitude of earthquake from its epicenter while the accleration scale uses Grms value to talk about the intensity of earthquake at the surface.

That is the reason the same magnitude earthquake can have less/high damage at surface level because of the difference in the location of epicenter from the earth's surface.

I think that to answer the question we need to know the structure of the acquisition system. For example sensors can be positioned "on site" (near the fault) or "on target" (near the buildings to control). If the sensors are near the fault where earthquake event begin evalueting accelerometric signals is possible find displacement signals (integrating the signal) so the magnitude. While if the sensors are distant from the earthquake origin is more difficult to estimate the values, because there is a propagation between source and acquisition.

Does Richter scale amplify the panic for earthquake strength ?

I do not understand your question.

Chris