Cepheid variables are valuable as distance markers because they are and their period of brightening is directly related to their

Luminous; distance travelled

Explanation:

Cepheids, also called Cepheid Variables, are stars which brigthen and dim periodically. This behavior allows them to be used as cosmic yardsticks out to distances of a few tens of millions of light-years. a uniform function of their brightness. The reason Cepheids can be used to determine distance is because the are variable stars that change brightness according to a regular pattern Cepheid variable discovery allows one to know the true luminosity of a Cepheid by simply observing its pulsation period. This in turn allows one to determine the distance to the star, by comparing its known luminosity to its observed brightness.

true. earthquakes are felt whenever there is a slip around a fault in the rocks below the earth. this reorientation of faults create sesmic waves and is known as earthquake, the severity of which is measured in richter scale. these are more prominent in hilly regions as the rocks usually form faults to balance the pressures on it.