A powerful earthquake of preliminary magnitude 7.8 struck today near the Iran-Pakistan border, according to the U.S. Geological Survey (USGS).

At least 40 people were killed and dozens injured, prompting Iranian officials to declare a state of emergency in the southeast provinces of Sistan and Baluchestan, according to reports from Iran's state media.

The temblor's epicenter was 53 miles (86 km) east-southeast of Khash, Iran. It originated 51 miles (82 km) deep, the USGS reports.

Earthquakes like the one that struck today can cause significant damage, especially with poorly built structures, and are sometimes followed by significant aftershocks. But the damage caused by any single event depends on the quake's depth, proximity to populated areas, building standards in the region, as well as the type of earthquake. The USGS frequently updates the magnitude of an event after more data is analyzed.

An earthquake's magnitude is a measure of the energy released at the source. It is just one predictor of the shaking that may ensue, which is affected by local and regional geology. Scientists know in a general sense what causes Earthquakes but are unable to predict specific quakes.

This article will be updated as more information becomes available. Find more earthquake news here.