Starquake

A star adjusts in 2004, temporarily blinding out every x-ray satellite in space.
A starquake is an astrophysical phenomenon that occurs when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth. This happens regularly as the neutron star spins down. The original shape of the star is a very flat ellipsoid due to centrifugal forces. As the rotational speed decreases, the shaped approaches a sphere. Since the crust is very stiff, this happens intermittently like an earthquake. The rotational speed of the star is measured with very high accuracy, so the star shape, size of quake, and stiffness of the crust is accurately measurable.
This may also be the source of the giant gamma ray flares that are produced approximately once per decade from soft gamma repeaters. Some suggests starquakes are caused by huge stresses exerted on the surface of the neutron star produced by twists in the ultra-strong interior magnetic fields.
The largest recorded event that some suggest was caused by a starquake occurred on the ultracompact stellar corpse (magnetar) SGR 1806-20. It released gamma rays equivalent to 1036 kW in intensity. This starquake occurred 50,000 light years away; if it occurred within ten light years of Earth, it would have caused a mass extinction.

http://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Earthquake