Anomalous dispersion

Definition

Anomalous dispersion refers to the phenomenon where the velocity of seismic waves varies in an unusual manner with frequency, typically resulting in lower velocities for higher frequencies. This behavior contrasts with normal dispersion, where wave speeds increase with frequency. Understanding anomalous dispersion is important for interpreting seismic wave propagation and analyzing the subsurface geological structures, especially in areas with complex geological features.

5 Must Know Facts For Your Next Test

1. Anomalous dispersion typically occurs in materials that have complex layering or are highly fractured, causing higher frequency waves to lose energy more rapidly.
2. In regions of anomalous dispersion, the arrival times of seismic waves can be significantly altered, complicating the interpretation of seismic data.
3. This phenomenon is often observed in sedimentary basins, where variations in porosity and fluid content can lead to unique wave propagation characteristics.
4. Anomalous dispersion can impact the accuracy of seismic imaging techniques, making it essential to account for in data processing and interpretation.
5. Understanding anomalous dispersion is crucial for reservoir characterization and monitoring, as it can provide insights into fluid distribution and geological features.

Review Questions

• How does anomalous dispersion differ from normal dispersion in terms of seismic wave behavior?
  • Anomalous dispersion differs from normal dispersion primarily in how seismic wave velocities change with frequency. In normal dispersion, wave speeds increase as frequency rises, while in anomalous dispersion, higher frequencies travel at slower velocities. This unique behavior can lead to complex interpretations during seismic data analysis, especially in geological formations where this phenomenon is prevalent.
• What implications does anomalous dispersion have for interpreting seismic data in sedimentary basins?
  • Anomalous dispersion can significantly complicate the interpretation of seismic data within sedimentary basins. The unusual variation in wave velocities with frequency can alter the arrival times and amplitudes of seismic signals, potentially masking critical geological features or leading to misinterpretation of subsurface structures. Therefore, it is essential to incorporate an understanding of this phenomenon into data processing techniques to improve the accuracy of seismic imaging and reservoir characterization.
• Evaluate the significance of understanding anomalous dispersion when analyzing subsurface geological structures and resources.
  • Understanding anomalous dispersion is vital for accurately analyzing subsurface geological structures and resources because it directly affects the propagation characteristics of seismic waves. As anomalies can provide insights into material properties and fluid distributions within geological formations, recognizing these variations allows geophysicists to make more informed predictions regarding resource locations and conditions. Moreover, accounting for anomalous dispersion enhances the reliability of seismic imaging techniques, ultimately contributing to successful exploration and resource management.

Related terms

normal dispersion:

A condition where the seismic wave speed increases with frequency, commonly observed in most geological materials.

seismic wave velocity: The speed at which seismic waves travel through different materials, influenced by factors such as density and elasticity.

attenuation: The reduction of wave amplitude as seismic waves propagate through a medium, which can be affected by scattering and absorption.