MK Geofisika Dasar-Pertemuan ke-3- Seismograf dan Gelombang Seismik Bagian 1

Summary

In this geophysics lecture, Nugraha from ITB introduces the fundamentals of seismographs and seismic waves. He explains the role of seismometers in recording ground motion in multiple directions (north-south, east-west, vertical) and discusses the evolution of seismograph technology. The lecture further covers the two main types of seismic waves: P-waves (primary, compressional) and S-waves (secondary, shear), detailing their properties, propagation, and speeds. The session emphasizes advancements in digital seismographs, showcasing smaller, lighter, and more efficient sensors. This concise presentation offers an engaging look at seismic wave dynamics and modern geophysical tools.

Takeaways

• 😀 Seismometers are instruments used to record ground motion in various directions (north-south, east-west, and vertical).
• 😀 Current seismometer technology allows for all directions of ground motion to be recorded digitally in one compact, efficient device.
• 😀 Modern seismographs are smaller, lighter, and more sensitive, improving accuracy and performance.
• 😀 Seismographs use digital data loggers and sensors powered by batteries for portability and reliability.
• 😀 Seismic waves are categorized into body waves (P-waves and S-waves) and surface waves, which propagate through the Earth's interior or on the surface.
• 😀 P-waves (Primary Waves) are the fastest seismic waves, traveling between 1.5 km/s to 8 km/s in the Earth's crust.
• 😀 P-waves are longitudinal waves, where particle movement occurs in the same direction as the wave propagation, resulting in compression and dilation.
• 😀 S-waves (Secondary Waves) are slower than P-waves and can only travel through solid media, not liquids.
• 😀 S-waves are transverse waves, with particle motion perpendicular to the direction of wave propagation.
• 😀 Seismic wave propagation can be visualized with animations, showing how P-waves and S-waves move through different mediums.

Q & A

What is the primary function of a seismometer?

A seismometer records ground motion or the movement of the Earth during seismic events such as earthquakes. It captures motion in different directions, including north-south, east-west, and vertical.

How do modern seismometers differ from earlier versions?

Modern seismometers are smaller, lighter, more compact, and more accurate than earlier versions. They have advanced to incorporate digital technology, allowing for precise data recording and real-time monitoring.

What is the significance of the 'ground motion' recorded by seismometers?

Ground motion refers to the movement of the Earth's surface during seismic events. Seismometers record this motion in multiple directions, helping scientists understand the intensity and direction of seismic waves and their impact on the Earth.

What are the two main types of seismic waves discussed in the script?

The two main types of seismic waves discussed are P-waves (Primary waves) and S-waves (Secondary waves). P-waves are compressional waves, while S-waves are shear waves.

How do P-waves (Primary waves) propagate through the Earth?

P-waves are compressional waves that travel fastest through both solids and liquids. They propagate by alternating compression and expansion of particles, with the particles moving in the same direction as the wave.

Why do S-waves (Secondary waves) travel slower than P-waves?

S-waves travel slower than P-waves because they involve shear motion, where particles move perpendicular to the direction of wave propagation. Additionally, S-waves can only travel through solid materials, which slows them down compared to P-waves that can travel through liquids as well.

What is the difference between the motion of particles in P-waves and S-waves?

In P-waves, the particles move in the same direction as the wave (compression and dilation). In S-waves, the particles move perpendicular to the direction of the wave (shearing motion).

What technological advancements have improved seismographs over time?

Technological advancements have made seismographs smaller, lighter, and more accurate. They now incorporate digital sensors, data loggers, and batteries, making seismic data collection more efficient and precise.

What does 'ground motion' refer to in the context of seismographs?

Ground motion refers to the movement of the Earth's surface during an earthquake or seismic event. It is measured by seismometers and recorded in different directions (horizontal and vertical) to provide comprehensive data about the seismic activity.

How does the velocity of seismic waves change when traveling through different layers of the Earth?

The velocity of seismic waves varies depending on the material they travel through. P-waves are faster than S-waves and can travel through both solid and liquid layers. S-waves, however, can only travel through solid materials, and they generally move slower than P-waves.