Last night’s earthquake was felt as far away as Moses Lake, North Bend, Skykomish and Ellensburg. Centered 10 km under…

Last night’s earthquake was felt as far away as Moses Lake, North Bend, Skykomish and Ellensburg. Centered 10 km under Lake Wenatchee State Park, the quake registered a 4.3 and not only shook the earth in Leavenworth but also created a series of loud booms.

Many people reported that the rumbling was so loud, they assumed a truck or heavy equipment had slammed into the building they were in. Kelly Cannata Coulter reported, “All is well at 59er Diner and Plain Hardware. Felt like a truck hit the diner, but thankfully, no damage.

On Icicle TV’s facebook page, we also received many stories of animals acting strangely before and during the quake. The strongest shaking was felt closest to the epicenter. Becky Fishburn at Tall Timber Ranch wrote “It shook long and hard – never felt anything like it! We had a Native American troupe dancing. It was amazing!”

To learn more about last night’s earthquake, we contacted local Geologist/Science Geek Rex Flake. Rex explained that the quake occurred in the Chelan seismic zone, which is a very active seismic area and in fact, the most active in all of Washington. The Chelan seismic zone was also the sight of the largest earthquake in Washington State history, which registered at 6.8 in 1872.

So far we have not received any reports of structural damage. According to Rex, the likelihood of damage depends on the depth of the epicenter, the type of substrate, and distance from epicenter as well as the magnitude. As far as earthquakes go, last night’s was fairly shallow at 10km underground.  Known as an intraplate quake, the movement occurred on a crack within our own seismic plate, rather than between two plates such as the San Andreas Fault. 

Why did some people in Leavenworth feel the quake and others did not?  Again, this depends on the substrate. Earthquakes are more easily felt above sediment fill, which amplifies the ground motion because the waves moving through rocks and sediment can reverberate like a speaker would. Our earthquake expert Rex actually didn’t feel the earthquake himself. Located on top of a rocky peak across from the Alpine Lakes Wilderness (yes, we should have added “adventurer” to Rex’s title), the shaking of the ground was dampened resulting in zero shaking or at least not enough to have taken notice.

And what about the loud booms that were heard?  Susan Deliduka of Leavenworth wrote, “We heard it more than felt it. Sounded like someone jumped onto the 3rd floor roof.” Rex theorizes that most of the sounds that were heard were rock slides generated by the earth’s movement. With the ground being highly saturated, it’s likely that large slides on peaks such as Mt Maude and Dirty Face were triggered. Closer to Leavenworth, rockslides occurred, just outside of town, as Stephen N Audrey Smith wrote, “heard rocks tumbling down through the timber on Tumwater Mountain.”

On a much less scientific note, in addition to rumbling, strange clouds were also viewed above the town of Leavenworth. Crisscrossed mares tails seemed to appear immediately after the quake and as it turns out, “earthquake clouds” have been rumored to portend earthquakes since antiquity. Real or not? The strange clouds seemed too strange to be a coincidence to us, although Rex cautioned any assumptions of correlation stating that it’s hardwired into our brains to find patterns in nature. We think it’s much more fun to believe in earthquake clouds though, so here are a couple of photos by ITV contributor Todd Smith as well as an ITV timelapse shot last night.

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Did you feel the earthquake? If so, head over to the USGS website and fill out their questionnaire.