Peru 5.1-Magnitude Quake Kills 6 in Junín, Injuring 21 and Affecting 200

Q: Why can't scientists agree on an earthquake's true power?

Scientists often disagree at first because an earthquake does not have one instantly knowable “true power.” Early estimates depend on which data arrive first, which instruments are used, and which magnitude formula an agency applies. That is why Peru’s quake was reported as 5.1 by local authorities, 5.5 by the U.S. Geological Survey and 5.6 initially by the European-Mediterranean Seismological Centre. Those are not necessarily contradictions so much as different preliminary calculations. As more seismic stations report in and analysts refine the quake’s depth, location and rupture characteristics, the number can change. Part of the confusion is that “power” can mean different things. Magnitude measures the energy released at the source; intensity measures how strongly the shaking was felt and how much damage it caused at specific places. A moderate quake can be deadly if it is shallow, close to towns, and strikes vulnerable buildings such as the adobe homes common in parts of Junín. Even magnitude itself is not a single perfect measure. Older scales such as local magnitude, often called Richter, rely on wave amplitude and can differ from moment magnitude, which better captures the total fault rupture and is now preferred for larger events. Depth, distance, local geology and incomplete early data—especially during aftershocks—also complicate estimates. So scientists usually converge on a best value, but not instantly, and not always from the same method.

3 articles · Updated · Bloomberg · Jul 19

Six people died after a 5.1-magnitude earthquake struck Peru’s central Junín region late Saturday, with 21 injured and about 200 others affected, authorities said.
The quake hit shortly after 9:20 p.m. local time, with its epicenter in the Andean province of Chupaca.
An aftershock followed about 15 minutes later as emergency crews began assessing damage across the region.
The tremor hit Peru’s central region just weeks after a separate earthquake in Venezuela, underscoring renewed seismic activity in the area.