A magnitude 6.4 earthquake struck Northern California early Tuesday, killing at least two people, damaging infrastructure, and knocking out power to tens of thousands.

"The most likely scenario is that this will be followed by a series of lesser earthquakes," the US Geological Survey tweeted Tuesday.

According to USGS estimates, there is a greater than 99% risk of magnitude 3 and above aftershocks over the next week, but only a 13% chance of magnitude 5 and above aftershocks.

What is an aftershock?
AFGHANISTAN-EARTHQUAKE
(Photo : WAKIL KOHSAR/AFP via Getty Images)

Aftershocks are minor earthquakes that occur in the days, months, or years following an earthquake. These are modest modifications made near faults or regions of tension during an earthquake.

Aftershocks can occur in the thousands and can be harmful or fatal. The "mainshock" is the most powerful activity felt during an earthquake.

To characterize the behavior of aftershocks, seismologists usually employ Bath's law, Gutenberg-Richter law, and Omori's law.

According to Bath's rule, aftershocks are generally 1.2 magnitude units smaller than the mainshock.

Based on the Gutenberg-Richter scale, every unit of magnitude reduction in earthquake magnitude should result in ten times the number of aftershocks.

Meanwhile, according to Omori's law, the number of aftershocks will decrease with time, according to a seismology lab at the University of California, Berkeley.

Swarms, which are sequences of minor earthquakes linked with geothermal activity but lack a recognizable mainshock, are not to be confused with aftershocks.

Foreshocks occur in the same place as big earthquakes. A foreshock may be misidentified as the mainshock until a bigger one happens after it.

Foreshocks and aftershocks cannot be larger than the mainshock.

A slide on a fault, which is a fracture zone between two blocks of rock, causes earthquakes.

The tectonic plates move, but their edges remain fixed until the tension overcomes the friction that ordinarily holds them in place.

This causes the remainder of the block to shift, causing energy waves to propagate through the earth's crust. These seismic waves pass through the ground, causing it to quake.

Also Read: At Least 65 People Dead as 6.5 Magnitude Earthquake Hits Southwestern China

What can I do to be prepared for an earthquake?

Begin by relocating furniture such as bookshelves away from beds, sofas, and other areas where people sit, sleep, or spend a significant amount of time.

Place heavier items on lower shelves.

Then secure items such as televisions, laptops, bookcases, furniture, unstrapped water heaters, and so on. See the "Get Started" section below, as well as the page's menu, which offers thorough instruction pages for many popular items.

Arranging for an earthquake or other calamity is similar to planning for a party or vacation.

Make sure your emergency plan contains evacuation and reunion arrangements, the name and phone number of your out-of-state contact person, the location of your emergency supplies, and other essential information.

Finally, have periodic earthquake "drills" to rehearse your strategy, and share it with individuals who look after your children, pets, or house.

Everyone should have emergency supplies in easily accessible places at home, work, and in their vehicles. Having emergency supplies on hand can help you and your family cope with an earthquake or other disaster.

You can put anything you want in each location:

Under-Bed Bags store shoes, a flashlight, and other belongings in case of an earthquake while sleeping.

When an evacuation is required, Go-Bags or automobile packs include provisions for around three days.

Home or work supplies are for people who plan to stay somewhere for up to two weeks or for bigger groups.

Earthquakes may last only seconds, yet they may cause havoc in our lives for weeks or months. You may reduce your financial stress by arranging crucial paperwork, fortifying your property (house or other building), and thinking about earthquake insurance.

Most houses, apartment complexes, and commercial structures are not as secure as they may be, especially if they are more than 30 years old.

While building rules have evolved through time, few demand the repair of flaws in older structures. There are, however, things you can do to improve the structural integrity of your home or other structure.

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