But before going into my topic of the day, I wondered why that huge  (#6 on all-time list ) earthquake did not produce a gigantic tsunami ( from the  Star-Advertiser ): The most recent event had an estimated magnitude of 8.7 or 8.8 on the scale scientists use to measure the strength of earthquakes.     By contrast, catastrophic tsunamis in the past, including a wave that struck Indonesia in 2004 and another that hit Japan in 2011, were generated by a quake of about magnitude 9.   That might sound comparable to Wednesday’s quake, Melgar said, but it is significantly bigger. That’s because the earthquake scale is logarithmic: A magnitude- 9 event possesses about 10 times as much energy as a magnitude-8.7 event, and about three times as much energy as a magnitude-8.8 event.   Also, current models suggest that Wednesday’s earthquake occurred across a stretch of seafloor that was hundreds of miles long. The longer the quake, the more energetic the...