Question

seismogram - group #4 - station c (barstow)
station c
arrival time
p - wave 4:31:08
arrival time
s - wave 4:31:39
s - p
lag time (s) 21
distance from
epicenter (km)
(kilometers)
4:31:00 am 4:31:30 am 4:32:00 am 4:32:30 am 4:33:00 am
local time of day
(hours : minutes : seconds)
earthquake epicenter activity
earthquake at geosciences research division, scripps institution of oceanography http://earthguide.ucsd.edu/
this project is produced with support from cosee california

Explanation:

To determine the distance from the epicenter, we use the S - P lag time. The formula relating S - P lag time ($t$) and distance ($d$) from the epicenter is $d = 10\times t$ (this is a simplified formula used in basic seismology for educational purposes, where $t$ is in seconds and $d$ is in kilometers).

Step 1: Identify the S - P lag time

From the table, the S - P lag time ($t$) is 2.1 seconds.

Step 2: Calculate the distance

Using the formula $d = 10\times t$, substitute $t = 2.1$ seconds into the formula.
$d=10\times2.1 = 21$ kilometers.

Answer:

The distance from the epicenter is $\boldsymbol{21}$ kilometers.