1. Thud! Ring! Seismic Response What causes a seismic response?
1. Changes in bulk-rock velocity or density
Lithology (e.g., sandstone, shale, limestone, salt)
Slide 3
What causes a seismic response?
It is changes in the velocity and/or density of the rock with fluid in the pore space
Several factors effect the velocity and density of bulk-rock
The most common factor is lithology
e.g., sandstones generally have different velocity and density values than shales or limestone.
Consider the last time you struck a hammer or pick against a rock
If you struck a dense limestone, the hammer would bounce back rapidly and the sound would have a high pitched ring
However, if your hammer struck a less dense shale, it would only yield a low pitched ‘thud’
The frequency of the sound you hear when your hammer strikes a rock is proportional to the density of that rock
Limestone
Ring!
Thud!
Shale
Courtesy of ExxonMobil
L Seismic Attributes