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Because of its accuracy in outlining the Earth's subsurface, the seismic-reflection method remains the most important tool in the search for petroleum reserves. In field practice, a subsurface is mapped by arranging a series of wave-train sources, such as small dynamite explosions, in a grid pattern. As each source is activated, it generates a wave train that moves downward at a speed determined uniquely by the rock's elastic characteristics. As rock interfaces are crossed, the elastic characteristics encountered generally change abruptly, which causes part of the energy to be reflected back to the surface, where it is recorded by seismic instruments. The seismic records must be processed to correct for positional differences between the source and the receiver, for unrelated wave trains, and for multiple reflections from the rock interfaces. Then the data acquired at each of the specific source locations are combined to generate a physical profile of the subsurface, which can eventually be used to select targets for drilling.
一朵乌云
[数学 ]【新版】冲分救命题 -11998
The integers a, b, and c are positive, and a>b>c. When a, b, and c are divided by 3, the remainders are 0, 1, and 1, respectively.
[数学 ]【新版】冲分救命题 -11997
For all positive even integers n. n* represents the product of all even integers from 2 to n, inclusive. For example, 12*=12×10×8×6×4×2. What is the greatest prime factor of 20*+22*?
[数学 ]【新版】冲分救命题 -11996
[数学 ]【新版】冲分救命题 -11995
[数学 ]【新版】冲分救命题 -11994
In a game, the cards in a certain deck are distributed to players one at a time until each player has the same number of cards and there are not enough cards left in the deck to distribute one more card to each player. The number of cards in the deck is between 60 and 100. If the cards in the deck are distributed o 5 players, 2 cards will be left in the deck. If the cards in the deck are distributed to 6 players, 4 cards will be left in the deck. If the cards in the deck are distributed to 7 players, how many cards will be left in the deck?
[数学 ]【新版】冲分救命题 -11993
Let a be the greatest integer such that is a factor of 1,500, and let b be the greatest integer such that is a factor of 33,333,333. Which of the following statements are true? Indicate all such statements.
[数学 ]【新版】冲分救命题 -11992
A set consists of all three-digit positive integers with the following properties.Each integer is of the form JKL,where J,K,and I are digits;all the digits are nonzero;and the two-digit integers JK and KL are each divisible by 9.How many integers are in the set?
[数学 ]【新版】冲分救命题 -11991
[数学 ]【新版】冲分救命题 -11990
The number of children in a certain family is a prime number less than 10. The number of boys in the family is greater than the number of girls, and the number of boys is a prime number. If at least 1 of the children in the family is a girl, which of the following could be the number of boys in the family?Indicate all such numbers.
[数学 ]【新版】冲分救命题 -11989
[数学 ]【新版】冲分救命题 -11988
x and y are integers.
[数学 ]【新版】冲分救命题 -11987
x and y are integers.
[数学 ]【新版】冲分救命题 -11986
a and b are distinct odd prime numbers.
[数学 ]【新版】冲分救命题 -11985
When the integer n is divided by 33, the remainder is 24. Which of the following must be a divisor of n?
[数学 ]【新版】冲分救命题 -11984
4.What is the length of an edge of the smallest solid cube that can be made by placing together solid rectangular blocks of size 7 by 6 by 3?
[数学 ]【新版】冲分救命题 -11983
Light travels at approximately 186,000 miles per second.Which of the following is closest to the number of miles that light travels in 3 hours.
[数学 ]【新版】冲分救命题 -11982
The number n is the least positive integer for which 108n is the square of an intege
[数学 ]【新版】冲分救命题 -11981
The number n is the least positive integer for which 108n is the square of an intege
[数学 ]【新版】冲分救命题 -11980
If x=2y+1, and y=2w, where w, x, and y are integers, which of the following must be an odd integer?
[数学 ]OG -11979
If x=2y+1, and y=2w, where w, x, and y are integers, which of the following must be an odd integer?
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