Union Pacific Corp. (UPC) announced second-quarter earnings of $154 million, up 7 percent from the second quarter of 1987.

Earnings per share were $1.35, an 8 percent gain over 1987. A company spokesman said strong growth in natural resources contributed significantly to the earnings gain. Revenues were $1.6 billion, compared to $1.5 billion in 1987.UPC subsidiary Union Pacific Railroad increased its earnings 3 percent to $115 million on revenues of $1.1 billion, a 12 percent gain. The company said record traffic levels were offset by higher fuel prices, greater personal injury and litigation costs, and increased maintenance expenses resulting from higher volumes.

Carloadings and revenue ton-miles were up 11 and 18 percent, respectively, with the major carloading gains in metals and ores (44 percent); energy (16 percent); autos (19 percent), and chemicals (9 percent).

Union Pacific Resources achieved a 25 percent earnings gain to $60 million. Exploration and production operating income improved 33 percent, from nearly $35 million to $46 million.

Higher volumes and the settlement of several natural gas contract disputes more than offset lower energy prices. Manufacturing and marketing income was $37 million, compared to $44 million in the second quarter of 1987, when a favorable adjustment was recorded applicable to the formation of a joint venture.

Resources' West Coast refinery achieved record earnings for the quarter, more than double last year. Operating income from UP Resources' mining operations more than doubled to $26 million, reflecting the sale of a half interest in the Prospect Point, Wyo., coal operation.

Overnite Transportation increased its earnings before goodwill amortization 49 percent to $15 million. Traffic gains of 13 percent, coupled with a 4 percent improvement in prices, increased revenues 17 percent to $158 million. Overnite's operating ratio of 86.3 percent remains one of the lowest for less-than-truckload companies.

Union Pacific Realty earned $3 million, compared to $6 million in the second quarter of 1987. Last year's results included three large real estate sales on the West Coast.

USPCI, Inc., acquired in the second quarter, had net income of $2 million vs. $3.5 million last year. Lower earnings resulted from cost increases associated with expansion plans.

In the first half, Union Pacific increased its net income 10 percent to $291 million. Union Pacific Railroad earned $235 million, up 6 percent; Union Pacific Resources had net income of $104 million, a gain of 17 percent; Union Pacific Realty earned $13 million, up 17 percent; Overnite earned nearly $26 milllion, a gain of 42 percent, and USPCI had net income of nearly $2 million, compared to $6 million in 1987.