1. Oceanography Practice Problems The following pages contain numerical word problems presented in lecture. There are two steps to solving word problems : 1)translate the wording into a numeric equation; –What are the variables, constants (for example, distance (d), rate ( r) 2)solve the equation! –This may first involve simplying the equation (combining like terms, etc)

2. Problem #1: Computing Longitude You are in the Pacific Ocean after having sailed from Santa Cruz 4 days earlier. It is noon (12:00) on the ship (local time), but a clock that keeps Santa Cruz time is at 3 PM (15:00). How many degrees of longitude have you traveled relative to Santa Cruz? Recall: 360° longitude / 24 hr = 15°/hr Solution: 15:00-12:00=3 hr 3 hr x 15°/hr = 45° You are 45° to the west

3. Problem #2: Water Depth You are in the Atlantic Ocean measuring water depth using sonar. The sonar records two way travel time (from ship to seafloor and back) of 3 seconds. Assuming that the average velocity of sound in seawater is 1.5 km/sec, determine the water depth in meters. Solution: d = r x t, r=1.5 km/sec, t=3 sec d =1.5 km/sec x 3 sec = 4.5 km 4.5 km/2 = 2.25 km 2.25 km x 1000 m/km = 2250 m

4. Problem #3: Computing Distance to Epi-center What do we know? V P = 8 km/sec, V S = 4 km/sec Difference in arrival time (∆T) between p and s waves = T S - T P Time it takes p and s waves to travel the same distance (D) T P = D/8, T S = D/4 ∆T between the P- waves and S-waves is: ∆T = T S - T P = D/4 – D/8 = 2D/8 - D/8 or ∆T = D/8 The distance D from the earthquake epicenter to seismic station is: D = 8 ∆T (constant is generally closer to 6) Example: S arrives 10 sec after P D = 8 ∆T = 8 km/sec (10 sec) = 80 km