Earthquake is a terrible natural disaster that can cause great damage in a very short time. One of the main reasons for the earthquake is due to various types of transfer or deviation of tectonic plates known as plate tectonic theory. According to the plate tectonic theory, earthquake occurs due to accidental movement of tectonic plates or moving up or down. There are many reasons for the movement of these tectonic plates. But the combined effects of the gravitational forces exerted by the moon, the sun and the other planets on the tectonic plates on earth's surface are one of the reasons for the movement of these tectonic plates which has never been discussed yet. Here In this article I will prove this with the help of some evidence. Surrounding the sun when the distance between Earth and other planets decrease or the planets come close to Earth, the gravitational forces between Earth and the other planets increase. As a result, the speed of the tectonic plates increase than usual and most of the major earthquakes occur at this time. When the planets move away from the Earth, the gravitational forces between Earth and the other planets decrease. At this time the minor earthquakes occur. We know, low tides and high tides occur due to the combined effects of the gravitational forces exerted by the moon and the sun on earth. Similarly, earthquakes are caused by the combined effects of the gravitational forces of the sun, the moon, and the other planets on Earth. It is the main basis of this study. Here in this article, firstly I will discuss how the combined effects of the gravitational forces exerted by the moon, the sun and the other planets occur earthquakes. In this case the masses, the positions, the movement of the tectonic plates and frictions among the tectonic plates will be discussed. Secondly, by observing the positions of the planets, the sun and the moon at the time of some major earthquakes in the last 100 years and all the earthquakes in 2018, I will prove that when the other planets come close to Earth or stay one by one on the same side of the Earth or the Earth stays in between the other planets, the major earthquakes occur and other time the minor earthquakes occur.