From a 1999 article (link below):

"In an enclosed basin, we will refer to the tsunami as the initial wave directly produced by the earthquake and the seiche as the harmonic resonance within the lake.

Three hypothetical earthquake scenarios are simulated. Faulting beneath the lake generates a tsunami followed by a seiche that can continue for hours with waves as large as 3 to 10 meters in height at the shore. Areas near the fault rupture will also subside and inundate as a result of fault displacement and elastic rebound."

From this, and other knowledge, I submit that an initial wave produced by a landslide into a lake is a tsunami, a large enough landslide would produce additional waves resonating to and fro in the lake, and they would be called seiches (or, collectively, a seiche). Also, any wave in a lake produced by a distant earthquake (one not immediately beneath or adjacent to the lake) would be a seiche. There is actually a word for tsunami created by a distant source - teletsunami- but this would not apply here, as that term only applies to tsunami that travel great distances across intervening waters.

The Lake Tahoe faults involved in this scenario are dip-slip (normal), and thus, with the proposed magnitudes (up to M7.2), would very likely be tsunamigenic. Barbara's linked article was very interesting, but primarily concerned with landslides. The link I've provided delves with some detail into the earthquake/tsunami/seiche hazard. Fairly easy reading and quite interesting.

Michael Williams
Arroyo Grande, CA USA

• Lake Tahoe Tsunami/Seiche