Praktikum Geologi Struktur 2024 - Modul 10. Prediksi Singkapan - 2. Penggambaran Struktur Geologi

Summary

This educational video in Bahasa Indonesia explores geological structure analysis, focusing on fault prediction, geological mapping, and field measurement techniques. The presenter discusses methods for determining strike, dip, and fault characteristics using tools like Smith Net and Wofenet. The video highlights the importance of accurate field data, including measurements of fractures and fault offsets, and demonstrates how to visualize and classify geological structures. Additionally, it delves into the interpretation of stress axes (Sigma 1, Sigma 2, Sigma 3) and introduces fault classification methods, providing an in-depth look at geological analysis and visualization techniques in structural geology.

Takeaways

• 😀 The video discusses geological prediction methods, particularly focusing on geological structures and how to model them effectively using various tools and software.
• 😀 The first part of the video explained the V-Law, while this section focuses on geological structure representation, especially in the context of field studies.
• 😀 Fieldwork and precise data collection are essential for geological analysis, such as measuring fractures, bedding, offsets, and strike-dip values.
• 😀 A study case is presented in the Semaka Fault region, emphasizing the importance of obtaining accurate primary data like fracture angles and offset measurements.
• 😀 After collecting data, plotting on a Smith Net is recommended for visualization of geological structures, especially in determining the strike and dip of faults.
• 😀 A key part of geological analysis involves projecting geological planes from specific data points, such as strike and dip values, to understand fault orientations.
• 😀 The video demonstrates how to use stress analysis to determine the positions of Sigma 1, Sigma 2, and Sigma 3, which are crucial for understanding fault behavior.
• 😀 A classification system called Andersen's classification is used to identify the type of fault based on the stress position (e.g., left-lateral or right-lateral fault).
• 😀 For fault analysis, the video explains how to measure shear and determine the direction of fault movement, using the azimuth and strike values.
• 😀 The concept of fold analysis is introduced, particularly how to determine the axial plane and hinge of an anticlinal fold based on specific dip values and measurements.
• 😀 The video concludes with a summary of the steps needed to complete geological mapping and analysis using the methods and tools discussed in the video.

Q & A

What is the main topic discussed in the video?

The main topic of the video is geological structural analysis, specifically related to geological mapping, fault prediction, and stress analysis using different techniques like contouring, projection, and measurement of geological features.

What does the presenter mention about the challenges of geological fieldwork?

The presenter highlights the challenge of not being able to visit every geological outcrop personally. Therefore, they focus on the techniques for predicting and analyzing geological structures remotely or based on data gathered in the field.

What tool does the presenter recommend for plotting geological data?

The presenter recommends using a 'Smith net' for plotting the data, specifically for determining strike and dip values, and later using software to help with the contour plotting.

What is the purpose of the 'Smith net' in the geological analysis?

The 'Smith net' is used to plot the strike and dip of geological features. By plotting the data points on the Smith net, the geologist can project and visualize the structural orientations and gather necessary measurements for further analysis.

How does the presenter explain determining the stress axes (Sigma 1, Sigma 2, Sigma 3)?

The presenter explains that the stress axes can be determined by analyzing the nodal planes and intersections of faults. Sigma 1, Sigma 2, and Sigma 3 are positioned based on the geometric relations of fault planes and their projections, and are essential for understanding the stress state in the region.

What geological structure is being analyzed using the 'Andersen classification' method?

The 'Andersen classification' method is used to classify the type of fault based on the orientation of Sigma 2. If Sigma 2 is nearly vertical, the fault is likely a strike-slip fault, which involves horizontal motion along the fault plane.

What does the presenter explain about the 'dextral' fault type?

The presenter explains that a 'dextral' fault, also known as right-lateral, occurs when the blocks on either side of the fault move horizontally to the right. This is determined by observing the relative motion along the fault and identifying that the right block moves to the right while the left block moves to the left.

What is the significance of the 'contour' plot in geological mapping?

The contour plot helps visualize the distribution and orientation of geological features such as faults and folds. It enables the geologist to create a 3D understanding of the geological structures based on the plotted data points and their projections.

What technique does the presenter suggest for analyzing a folded geological structure?

For analyzing a folded geological structure, the presenter suggests using the concept of axial planes and projecting the fold structure to identify the hinge lines and the orientation of the fold. This is essential for understanding the geometry of folds, such as anticlines and synclines.

What method does the presenter recommend for determining the fold axis in a fold structure?

The presenter recommends using the King method for projecting and measuring the dip of the geological features. This method helps determine the correct orientation of the fold axis by projecting the structure vertically and horizontally to understand its 3D geometry.