9.0 Earthquake strikes Japan

[aslkahuna]

Yes, the Japanese are definitely much more disaster-conscious than Americans. The tsunami warning siren went blaring and everyone headed for the hills.

That's because the Country is much more prone to disasters with the big four (earthquake, eruption, tsunami, and typhoon) hanging over them at all times. They may also have gone into the upper floors of the high rises. From what I could see on the video is that the wall did hold and that people were on top of it. but the portions of the town outside the wall were trashed. The location and construction of the wall was covered in a National Geographic Video.

Steve

[HurricaneJosh]

That's because the Country is much more prone to disasters with the big four (earthquake, eruption, tsunami, and typhoon) hanging over them at all times. They may also have gone into the upper floors of the high rises. From what I could see on the video is that the wall did hold and that people were on top of it. but the portions of the town outside the wall were trashed. The location and construction of the wall was covered in a National Geographic Video.

Steve

Hey, Steve-- dumb question: can California get really huge tsunamis like these ones in Honshu? It seems like when we get them, they're relatively small. Does the local topography limit the potential, or is it simply that we don't get these really, really huge quakes in CA like they get around the "Ring of Fire"? If the San Andreas slipped big-time and we had, say, an 8.3, would Santa Monica, Marina Del Rey, the Pacific Palisades, and Malibu be under a similar threat, like Sendai?

[famartin]

You might want to check your math. The boats, especially from Sendai on to the north, didn't have time to get 10-20 miles off shore. Remember, the tsunami wave translates at roughly 500 mph. The earthquake happened less than 100 miles from Sendai. That means any boats in that area MIGHT have had 12 minutes...if they were lucky and responded IMMEDIATELY...to get away from whereever they were at.

As noted elsewhere, that speed only checks in open water. Near the coast, it slows considerably. So you can add a few minutes.

[famartin]

Hey, Steve-- dumb question: can California get really huge tsunamis like these ones in Honshu? It seems like when we get them, they're relatively small. Does the local topography limit the potential, or is it simply that we don't get these really, really huge quakes in CA like they get around the "Ring of Fire"? If the San Andreas slipped big-time and we had, say, an 8.3, would Santa Monica, Marina Del Rey, the Pacific Palisades, and Malibu be under a similar threat, like Sendai?

I'm no expert and am just gleaming off of others knowledge here, but from what I understand, you really need a subduction fault to produce a big tsunami. I don't think there are any in SoCal... but there may be one up north. Of course, the coastline's orientation would seem to limit the effects of such a tsunami.

[on_wx]

if you wanna know how great the alarm system is in Japan, take a look at this video:

http://www.youtube.com/watch?v=dmxb6hmydWs

the early warning system kicked in as soon as the earthquake was recorded; several prefectures were already placed under a tsunami alert, and after a minute or so, the you can see the actual shaking...

this is in the national assembly afaik... it's amazing how the reporter was able to stay calm even if his whole office is shaking already, although you can hear the "fear" in his voice in the latter part...

Here's the earthquake warning system from a different quake, but with subtitles

http://www.youtube.com/watch?v=yQQ848lNrCg

[Derecho!]

Hey, Steve-- dumb question: can California get really huge tsunamis like these ones in Honshu? It seems like when we get them, they're relatively small. Does the local topography limit the potential, or is it simply that we don't get these really, really huge quakes in CA like they get around the "Ring of Fire"? If the San Andreas slipped big-time and we had, say, an 8.3, would Santa Monica, Marina Del Rey, the Pacific Palisades, and Malibu be under a similar threat, like Sendai?

The San Andreas is a strike slip fault and is inland in Southern California, so it can't generate a tsunami (However, the 1989 quake near San Francisco actually caused a small tsunami because there was a thrust component).

HOWEVER, there are a bunch of thrust faults and strike-slip faults with restraining bends offshore Los Angeles in the Channel Islands, and an earthquake of 7-7.5 or so on these faults (or an earthquake followed by an underwater landslide) could generate a large and damaging local tsunami.

http://cwis.usc.edu/...GRL_tsunami.pdf

[aslkahuna]

Northern California can from Mendocino North because that's the southern limit of the Cascadia Subduction Zone. The San Andreas is mostly a strike slip fault which is the wrong kind for producing tsunamis besides being inland. I say mostly because certain segments of it (like in the Sant Cruz Mountains and where it is closest to the Transverse Ranges have a thrust component to its slippage. So too does the segment offshore from SFO. In fact, reports from 1906 indicate unusual tidal flows in the Bay after the main shock. However, that does not mean that Los Angeles is off the hook. There are a number of offshore thrust faults that can cause shocks strong enough to produce damaging tsunamis along the coast between Conception and San Diego. In fact, tsunamis were noted with earthquakes off the coast west of San Luis Obispo in 1812 and 1927. Given the proximity of the Channel Islands Thrust Fault, a strong shock of Northridge size or greater could result in a significant tsunami arriving onshore in the L.A. area mere minutes after the shock. Also too, there's always the (very) remote possibility of an impact generated tsunami.

Steve

[Mallow]

Hey, Steve-- dumb question: can California get really huge tsunamis like these ones in Honshu? It seems like when we get them, they're relatively small. Does the local topography limit the potential, or is it simply that we don't get these really, really huge quakes in CA like they get around the "Ring of Fire"? If the San Andreas slipped big-time and we had, say, an 8.3, would Santa Monica, Marina Del Rey, the Pacific Palisades, and Malibu be under a similar threat, like Sendai?

It's not really the size of the earthquake that determines whether or not there will be a tsunami, but the type.*

Basin-wide tsunamis are generally caused by subduction-zone earthquakes. This is because these kinds of earthquakes cause significant vertical movement of land under the ocean at the boundary between the plates, which induces the tsunami. These kinds of earthquakes produce the biggest tsunamis along the coast nearest the zone of slippage. A map of subduction zones is shown here:

http://pubs.usgs.gov/circ/c1187/images/fig03.jpg

So, the Pacific Northwest is at risk of this kind of earthquake/tsunami.

Because the San Andreas is a strike-slip fault (ignoring the fact that it's mostly located on land), it generally can't induce a large tsunami.

* However, smaller-scale tsunamis induced by other mechanisms such as underwater landslides and volcanism can be as large or larger in very localized areas. The landslides could be triggered by large earthquakes. The tsunamis that these produce are generally very destructive only right near the event in question.

EDIT: Ya, what Steve and Derecho said.

[HurricaneJosh]

Thanks, Steve, Derecho, and famartin-- appreciate it. Interesting stuff. I didn't know that smaller quakes could produce tsunamis, too.

And, thanks, Derecho, for the link to the very interestng paper! For those who didn't check it out, it says they've modeled tsunamis as high as 6 m for L.A.-Metro coastal areas.

[HurricaneJosh]

P.S. I'm realizing the complete silliness now of asking whether a San Andreas event would produce a tsunami on CA's shores, given that it's mostly on land in CA. Not using my brain today.

[k***]

what's the elevation of LAX? We might see another airport tsunami if 6m is possible.

[on_wx]

what's the elevation of LAX? We might see another airport tsunami if 6m is possible.

Elevation: 125 ft. / 38.1 m (surveyed)

[k***]

interesting factoid:

The average GDP of countries affected by today’s Tsunami is: 318,411,000 millions of dollars. Of the 2004 Indian Ocean Tsunami: 2,122, 539 millions of dollars.

[k***]

Elevation: 125 ft. / 38.1 m (surveyed)

it's got to be lower than that near the end of those runways...LAX and Logan both seem similar to me in terms of it being one of those ocean meets airport scenarios.

[on_wx]

it's got to be lower than that near the end of those runways...LAX and Logan both seem similar to me in terms of it being one of those ocean meets airport scenarios.

126ft according to multiple, if not all, Google search sources.

[Normandy]

Tsunami's would not push that far inland along the coastline in So Cal...the elevation rises pretty quickly (see Santa Monica).

[famartin]

it's got to be lower than that near the end of those runways...LAX and Logan both seem similar to me in terms of it being one of those ocean meets airport scenarios.

Its closer to 100 feet on the western end of the runways, but there's quite a drop-off between the end of the runways and the ocean.

[Mallow]

if you wanna know how great the alarm system is in Japan, take a look at this video:

http://www.youtube.com/watch?v=dmxb6hmydWs

the early warning system kicked in as soon as the earthquake was recorded; several prefectures were already placed under a tsunami alert, and after a minute or so, the you can see the actual shaking...

this is in the national assembly afaik... it's amazing how the reporter was able to stay calm even if his whole office is shaking already, although you can hear the "fear" in his voice in the latter part...

That's pretty incredible.

At 1:45 when the reporter first comes on, he says "it has arrived at the Tokyo Station/studio" or something like that.

Just before 2:15, he says something like "strong shaking has arrived at the Tokyo Station/studio now".

At just after 2:25, I'm guessing he's saying "now, violent shaking has arrived at the Tokyo Station/studio".

I could be wrong, but that's the best I can figure.

[k***]

Tsunami's would not push that far inland along the coastline in So Cal...the elevation rises pretty quickly (see Santa Monica).

venice beach is toast

Its closer to 100 feet on the western end of the runways, but there's quite a drop-off between the end of the runways and the ocean.

i guess it's hard to gauge from a plane.

[hoosierwx]

Animation of the 1700 Cascadia Tsunami

http://serc.carleton.edu/redirect.php?r=http%3A%2F%2Fwww.pgc.nrcan.gc.ca%2Fpress%2Fimages%2F2003JB002521-animation.gif

[HurricaneJosh]

Tsunami's would not push that far inland along the coastline in So Cal...the elevation rises pretty quickly (see Santa Monica).

Santa Monica would be mostly OK, but Marina Del Rey, Venice, and South Bay communities would get wiped. A lot of Marina Del Rey is only a little above sea level.

[Derecho!]

Tsunami's would not push that far inland along the coastline in So Cal...the elevation rises pretty quickly (see Santa Monica).

Generally a good policy to head inland if you're on the beach and feel an earthquake in Southern California; there's no tsunami warning system and a tsunami from the Channel islands would be on you in a few minutes.

[famartin]

venice beach is toast

i guess it's hard to gauge from a plane.

Topo of the western end of LAX's runway complex:

[k***]

Animation of the 1700 Cascadia Tsunami

http://serc.carleton.edu/redirect.php?r=http%3A%2F%2Fwww.pgc.nrcan.gc.ca%2Fpress%2Fimages%2F2003JB002521-animation.gif

that translated surprisingly nicely...i bet the marianas got rocked

[baroclinic_instability]

Animation of the 1700 Cascadia Tsunami

http://serc.carleton...1-animation.gif

That is a nice animation of that event. It also happens to look like the vertical velocity fields in the NAM when it blows up spurious convective blobs.

[HurricaneJosh]

Generally a good policy to head inland if you're on the beach and feel an earthquake in Southern California; there's no tsunami warning system and a tsunami from the Channel islands would be on you in a few minutes.

Good to know this. Honestly, I think there's very little tsunami awareness in SoCal. I never even hear residents mention it after a quake, and I've never even factored it into my safety plans. (I live 10 mi inland at a good elevation, anyway, so it's not like I'd need to evacuate.)

[aslkahuna]

About the other subduction zones-parts of the Alaskan slipped in 1964 and 1957 while Kamchatka had action in 1950. I believe that Peru had a biggee in the early 20th Century while Cascadia slipped in 1700. Also the zone off Mexico slipped in 1985. The problem with all this lies with the seismic gaps where nothing has happened for sometime while all hell broke loose around them. There's a particularly pesky one off Japan about 100 miles SW of Tokyo, the area east of Luzon down to Mindanao, another in Indonesia, Mexico, Central America and others. Also pesky for Tokyo is the triple point south of Tokyo (there's one of those off Northern CA west of Mendocino).

Steve

[HurricaneJosh]

It's not really the size of the earthquake that determines whether or not there will be a tsunami, but the type.*

Basin-wide tsunamis are generally caused by subduction-zone earthquakes. This is because these kinds of earthquakes cause significant vertical movement of land under the ocean at the boundary between the plates, which induces the tsunami. These kinds of earthquakes produce the biggest tsunamis along the coast nearest the zone of slippage. A map of subduction zones is shown here:

http://pubs.usgs.gov/circ/c1187/images/fig03.jpg

So, the Pacific Northwest is at risk of this kind of earthquake/tsunami.

Because the San Andreas is a strike-slip fault (ignoring the fact that it's mostly located on land), it generally can't induce a large tsunami.

* However, smaller-scale tsunamis induced by other mechanisms such as underwater landslides and volcanism can be as large or larger in very localized areas. The landslides could be triggered by large earthquakes. The tsunamis that these produce are generally very destructive only right near the event in question.

EDIT: Ya, what Steve and Derecho said.

I missed this post before-- gracias for the info.

P.S. I wasn't using my head when I asked if the San Andreas could produce a tsunami in CA-- as the whole setup obviously makes no sense.

[aslkahuna]

That is a nice animation of that event. It also happens to look like the vertical velocity fields in the NAM when it blows up spurious convective blobs.

Japan actually had a significantly damaging tsunami from that one.

Steve

[on_wx]

Animation of the 1700 Cascadia Tsunami

http://serc.carleton...1-animation.gif

CBC produced an amazing documentary in 2009 called 'Shockwave' about the next Cascadia tsunami. The doc prompted many BC coastal towns to put up tsunami sirens like in Hawai'i and hold yearly evacuation drills.

There was a team of scientists in the doc that used the model from the 1700 tsunami to make a "virtual" tsunami on the coast of BC, so it looked like a video game, it was horrendous. They also built a scale model of Seaside, OR in a wave pool and blasted waves at it. They did so much in the documentary. The trailer is on Youtube.