Task: Question Answering
Input (English): Context: An earthquake is sudden ground movement caused by the sudden release of energy stored in rocks. Earthquakes happen when so much stress builds up in the rocks that the rocks rupture. The energy is transmitted by seismic waves. Earthquakes can be so small they go completely unnoticed, or so large that it can take years for a region to recover. The description of how earthquakes occur is called elastic rebound theory (Figure 1.1). Elastic rebound theory. Stresses build on both sides of a fault, causing the rocks to deform plastically (Time 2). When the stresses become too great, the rocks break and end up in a different location (Time 3). This releases the built up energy and creates an earthquake. Click image to the left or use the URL below. URL: In an earthquake, the initial point where the rocks rupture in the crust is called the focus. The epicenter is the point on the land surface that is directly above the focus (Figure 1.2). In the vertical cross section of crust, there are two features labeled - the focus and the epicenter, which is directly above the focus. Click image to the left or use the URL below. URL: 
 Question: when an earthquake happens, we say that its __________ was located 100 miles northwest of san francisco.
Output (English): epicenter