Academic journal article Journal of Geoscience Education

Development of a Low Cost, Portable Multi-Channel Seismic Data Acquisition System for Classroom Experiments and Independent Studies

Academic journal article Journal of Geoscience Education

Development of a Low Cost, Portable Multi-Channel Seismic Data Acquisition System for Classroom Experiments and Independent Studies

Article excerpt

ABSTRACT

Ongoing integration of technology with geology requires today's geoscience students to develop solid geotechnical skills. Recent advances in analog-to-digital technology enable easy and inexpensive construction of a multi-channel seismic data collection system that can be used to teach students the fundamentals of seismology. Here I demonstrate how to construct and use a simple multi-channel seismic device for class experiments. The experiments act as a solid foundation for anyone hoping to develop active-source classroom seismology laboratories. In particular, the experiments give students hands-on experience with designing seismic surveys, data collection, and data processing and should compliment any introductory seismology or geophysics course.

INTRODUCTION

Though seismology represents a fundamental element of any geology and geophysics curriculum, it remains difficult for students to obtain hands-on seismic field experience without a geology department investing significant funds (generally in excess $10,000) into a seismic data acquisition system (e.g. Husebye et al. 2003, Steeples and Miller 1990). These expensive systems often include canned "black-box" software packages and data management programs that offer students only limited insight into how seismic data are recorded and processed. As a result, geology students frequently receive minimal or no seismic field and data processing experience, resulting in a limited understanding of basic geophysical principles and poor preparation for advanced geophysics work.

Here I snow how to construct an inexpensive multi-channel seismic data acquisition system that can be used in a wide range of seismic experiments, enabling students to obtain direct experience in seismic data collection and analysis. Using this instrument, I describe a few simple seismic experiments that give students exposure to seismic data collection and insight into geophysical methods. Furthermore, I give examples of asic seismic programs and scripts that can be written to process the data. The experiments should act as a good starting-point for anyone interested in designing a basic set of labs for an introductory seismology class.

CONSTRUCTING A LOW-COST SEISMIC DATA ACQUISTION SYSTEM

Recent advances in analog-to-digital technology allow easy construction of an inexpensive seismic data acquisition system. Constructing the system requires four key components: (1) a receiver, such as a geophone (or geophones), (2) an analog-to-digital converter, (3) a data collection and storage device, such as a laptop computer, and (4) a trigger mechanism such as a piezoelectric crystal mounted on a sledgehammer (Figure 1). Assuming access to a laptop computer, the total cost of constructing the seismic data acquisition system should be less than $1000.00.

Each of the components of the seismic data acquisition system can be obtained easily at minimal cost. Used geophones can be purchased readily from a variety of dealers. Most geophones are constructed with high-pass frequency filters so that unwanted low frequency seismic noise is filtered out and higher frequency sounds created by the seismic source are recorded. For example, "10 Hz Geophones" record seismic frequencies greater than 10 Hz, and "100 Hz Geophones' record seismic frequencies greater than 100 Hz (for a more detailed description, see Burger, 1992). The higher the bandpass filter of the geophone, the higher the price, and as a result, 100 Hz geophones are significantly more expensive than 10 Hz geophones. Nonetheless, most geophones can be purchased for less than $100 each, and inexpensive 10 Hz geophones generally work well for shallow seismic refraction work.

The analog-to-digital converter (ADC) is the key component in the seismic data acquisition device and must be chosen carefully. A variety of ADCs exist; I suggest one that can plug directly into a laptop PCMCIA port, since these devices are compact and easy to transport. …

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