Seismometers

[moonflower]

Hi everyone, SO im new to this but im desperate for a little help understanding something...

Seismometers. the time that elapses between an earthquake and it being recorded by the seismometer depends on what factors? Is it the different type of waves?

 

ANY help would be incredibly appreciated! Thanks in advance!

[OSHMUNNIES]

Good question, moonflower...seismometers can read 2 different types of waves; P-waves, which are compressional in nature, and S-waves, or shear waves. S-waves, which are defined by a side-to-side undulating movement, not only have a slower seismic velocity than P-waves, but are also restricted to brittle materials (they cannot travel through liquid, i.e. magma).

That said, the time elapse between seismic activity and the seismic reading is not only dependent on distance, but on the characteristics of the material transmitting the waves. Such properties as density, compressibility, and response to shearing, are among those that have the greatest affect on seismic velocity. For example, denser rocks will transmit P-waves more easily, allowing for a higher seismic velocity.

[moonflower]

Thanks so Very much,

 

Would you be able to help me with the following..... From a seismogram i have worked out that the s wave arrived 9.5mins after the first p wave how do i estimate the epicentral angle from this when i don't have the depth of the epicentre? Is there a formula?

 

Thanks AGAIN in advance!