Earthquake chainsaws are powered by Viper-Engines. I was not able to locate many reviews for this chainsaw brand primarily because they are not so popular. It is also difficult to comment on their quality because there are some rumours that their products are manufactured in China. In the end you get what you pay for and this is the reason that most of their saws occupy lower positions on the price chart.
I am in a process to review this company and I will surely update this article further. In the meantime you can have a look towards their top models.