Property, Plant and Equipment

12 Months Ended

Sep. 30, 2011

Property, Plant and Equipment [Abstract]

Property, Plant and Equipment

4.    Property, Plant and Equipment

Property, plant and equipment, together with the related estimated useful lives, were as follows:

	September 30,
	2011			2010			Useful Lives
Land, building and other	$	7,532,000		$	6,467,000			3 to 40 years
Recording equipment		199,347,000			155,949,000			5 to 10 years
Vibrator energy sources		65,175,000			59,103,000			10 to 15 years
Vehicles		30,337,000			27,133,000			2 to 10 years
Other(a)		256,000			291,000			—
		302,647,000			248,943,000
Less accumulated depreciation		(156,106,000	)		(130,900,000	)
Net property, plant and equipment	$	146,541,000		$	118,043,000

(a) Other represents accumulated costs associated with equipment fabrication and modification not yet completed.