Property, Plant and Equipment (Tables)

12 Months Ended

Sep. 30, 2013

Summary of Property Plant and Equipment

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

	September 30,
	2013			2012			Useful Lives
Land, building and other	$	10,822,000		$	8,641,000			3 to 40 years
Recording equipment		197,134,000			206,642,000			5 to 10 years
Line clearing equipment		937,000			913,000			5 years
Vibrator energy sources		80,309,000			76,813,000			5 to 15 years
Vehicles		35,623,000			32,429,000			1.5 to 10 years
Other(a)		639,000			592,000			—
		325,464,000			326,030,000
Less accumulated depreciation		(152,231,000	)		(164,634,000	)
Net property, plant and equipment	$	173,233,000		$	161,396,000

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