Answer: Our wavelength will be 2333.3 m.
Explanation:
Since we have given that
Wave speed = 7 km/ s
Frequency = 3 Hz
We need to find the wavelength of an earthquake wave:
As we know that :

First we convert km/sec to m/sec.
So, 7 km/sec= 7000 m/sec
so, our wavelength becomes

So, our wavelength will be 2333.3 m.