BASE GEOPHYSICS

When the shaking of the Earth's ground (known as earthquake) occurs at several times, then it is due to release and movement of energetic waves called seismic waves. Without ruining time,. I don't want to dig deeper on this topic, but just give you the basics regarding these waves. Stay alerted! Seismology is the study of seismic waves and Earthquakes. This may include the study of vibration, propagation, types and application of these seismic waves through the Earth. The term seismology originated from two Greek words " Seismos " means Earthquake and " Logos " means study of. The study of these waves is important as it gives clues regarding, ➔ It used to study the structure and nature of Earth's interior. ➔ It is used in seismic exploration geophysics. Note: The main source of seismic waves in nature is produced from Earthquakes. However there are man made sources of seismic waves such as dynamites, Vibrators forexample vibroseis. Although due to heter...

The first seismographs were built in the late 19th century were a mechanical synthesis of sorts - a seismometer rigged up to transfer its motions to some kind of timekeeping and recording device. Records, which became known as seismograms , were made continuously, by a pen tracing ink lines on paper, or a stylus etching smoked paper, with time "ticks" marked periodically to provide temporal reference points. See figure (3 and 4). What is a Seismograph? Seismograph Is the sensor device used to amplify and detect ground vibrations. Sometimes the word Seismometer is used to infer the same device. Seismographs basically consist of two (2) parts which are, 1. A seismometer: This is a sensor of ground motion 2. A seismic recording system. Basic Working Principle How does a seismograph work? Principle used by the seismometers, is that It works by " Inertia principle" . The most common is by using a mass suspended by a spring. This mass follows the motion of the ground...

What is Seismic Attenuation? Seismic Attenuation can be defined as the decrease in amplitude of seismic waves as the distance increases away from the source. Why do seismic waves attenuate ? The main causes of seismic energy loss through materials (rocks) medium during propagation are  1. Geometrical Spreading   This is the most important cause of seismic energy loss as it spreads from source and takes a spherical shaped path. Consider the figure 1, as shown below Figure 1: Seismic spread from the explosive source in spherical path  Amplitude density = Energy/Surface area of wavefront. A = E/4πr 2 A is inversely to radius (distance) for surface waves, Since surface waves take circular path as 2πr A is inversely to radius (distance) square for body waves, as body waves take spherical wavefront. See figure above. 2. Frictional Dissipation As frictional heating due to imperfect elastic of materials (rocks). This is also known as intrinsic attenuation or absorption . Also A...