Regional Geology

Microtremor basically a micro vibration of ambient ground motion, known as the earth noise, seismic noise or microseimic sourced from human activities (such as transport activities and industrial activities) and the natural vibration (such as wind and sea waves). Microtremor generally has an amplitude ranging from 1 to 10 micrometers.
Based on its period range, mikrotemor generally classified into two main sections namely;
1. Microtremor short period of analysis period microtemor with less than 1 second, related to the exploration of shallow subsurface structure (less than 100 meters from the surface).
2. Microtremor long period of analysis period microtremor with more than 1 second, related to the exploration of subsurface structure is more in the moment S wave velocity reaches 3500 m / s.

Currently Microtremor applications often used to estimate direct vibrational characteristics of the ground, one with a comparative analysis of the horizontal-vertical spectrum of recording microtremor (Nakamura, 1989) while another application is applied to exploration of subsurface structure determination of the depth and thickness of basement rocks Stratigraphy. In the case of subsurface exploration, in comparison with other geophysical methods microtermor has several advantages, among others; do not need artificial sources, exploration costs are relatively inexpensive, easy data acquisition and friendly to the environment. Because of its environmentally friendly and can use as a source of human activity, it is suitable microtremor in urban areas are densely populated and has any critical infrastructure and buildings.
Until now we have developed several methods to analyze the results of which are microtremor;
1. Analysis of spatial autocorrelation(Aki, 1957)
2. Analysis of the frequency spectrum and wave numbers (Capon, 1969)
3. Comparative analysis of the spectrum horizontal-vertical (H / V) (Nakamura, 1989)
In general, autocorrelation spatial analysis methods and analysis frequency spectrum and wave numbers are used to estimate the subsurface structure of the basement depth determination of layer thickness Stratigraphy and rock, while the comparative analysis horizontal-vertical spectrum is used to estimate ground vibrational characteristics.

This entry was posted on Monday, September 14th, 2009 at 7:24 am and is filed under Earthquake. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.