var qDuration=600;
var qCounter=0;
function quake()
{
    var deltaX=1;   // the horizontal displacement
    if (window.moveBy)
    {
        for (qCounter=0; qCounter<qDuration; qCounter++)
        {
            // shake left
            if ((qCounter%4)==0) { window.moveBy(deltaX, 0); }
            // shake right
            else if ((qCounter%4)==2) { window.moveBy(-deltaX, 0); }

            // speed up or slow down every X cycles
            if ((qCounter%30)==0)
            {
                // speed up halfway
                if (qCounter<qDuration/2)
                {
                    deltaX++;
                }
                // slow down after halfway of the duration
                else
                {
                    deltaX--;
                }
            }
        }
    }
}

function startEQ()
{
	richter=5;
	window.moveBy(0,richter);
	window.moveBy(0,-richter);
	window.moveBy(richter,0);
	window.moveBy(-richter,0);
	timer=setTimeout("startEQ()",10);
}
function stopEQ()
{
	clearTimeout(timer);
}