The ship wasn't more than a few miles long....doubtful that it would pull on the oceans (if Vulcan had any); much less cause earthquakes.
It seems highly unlikely that a mining drill would knock out all communication around the globe. The fact that Vulcan sent a message to Starfleet would indicate communications were operational. The Enterprise experienced problems probably because they were so close to the ship, not because the ship blacked out the solar system. Given Vulcan was a founding member of the Federation, it would make sense that there would be defenses both in near orbit or on the ground. Also, there should be defenses (ships, emplacements, ect) in other parts of the solar system. If the emplacements were out of range(with transporters having ranges in the millions of miles, surely phasers have firing ranges that dwarf TOS), then surely a ship within the system should be able to see whats going on and report to the Vulcan high command. In a system like Vulcan, there should be hundreds, if not thousands of ships (civillian and military) flying around.