There is a deep trench in the sea floor off the Marianas volcanic arc of explosive, andesitic, Ring of Fire volcanoes in the South Pacific, but the water is not deep off the coast of Oregon and Washington near Mt. St. Helens and the Olympic, because:.
A) The Marianas, Oregon and Washington have trenches, but the trench off Oregon and Washington is filled by discarded Microsoft Windows CDs that are obsolete because of all the virus problems.
B) Oregon and Washington are near a subduction zone, but the Marianas are not.
C) The Marianas, Oregon and Washington have had the sea floor bent downward by subduction to make trenches, the trench off Oregon and Washington is filled by sediment eroded from the nearby continent, but the Marianas don't have a nearby continent and so the trench there is not filled with sediment.
D) The trench off Oregon and Washington is filled with great basaltic lava flows from the hot spot that feeds the Cascades volcanoes.
E) The Marianas are near a subduction zone, but Oregon and Washington are not.

C) The Marianas, Oregon and Washington have had the sea floor bent downward by subduction to make trenches, the trench off Oregon and Washington is filled by sediment eroded from the nearby continent, but the Marianas don't have a nearby continent and so the trench there is not filled with sediment.

answer at the divergent plate boundary in the middle of the ocean;

hola:

ef0: daños leves. algunas tejas caídas y otras pequeñas piezas de los tejados arrancadas, algunos daños en canaletas, ramas de árboles rotas y algunos árboles poco profundos arrancados. los tornados que no causan daños visibles (por ejemplo aquellos que se producen en campos abiertos) se valoran siempre como de ef0.

ef1: daños moderados. tejados seriamente despedazados, caravanas y casetas volcadas o seriamente dañadas, perdida de puertas exteriores y ventanas y otros cristales rotos.

ef5: daños increíbles. las casas fuertes pueden quedar arrasadas hasta los cimientos, las estructuras de hormigón armado dañadas críticamente, los edificios altos sufren graves deformaciones estructurales. devastaciones increíbles.

y según esto creo que puedes sacar tus conclusiones. y la verdad la escala ef10 si no se decirte por que no la eh visto o mejor dicho estudiado. espero que te sirva. suerte.