now tonight it gives me great pleasure to introduce our speaker this evening dr. graham kent my graham is a research geophysicist and he's the director of the SI o visualization Center he's also been a great friend and supporter of the aquarium for a long time and in fact two years ago he was a member of our external review panel where we were looking to see how we would develop the aquarium in the future and also recently he was a very important advisor for our present earthquake exhibit which if you haven't seen it I hope you'll have a look after this evening's lecture he obtained his Bachelor of Science degree at San Diego State and his PhD here at Scripps Institution of Oceanography however all you really need to know about Graham is that he's one of the world's greatest reflection seismologists now simply put that means he collects images that allow him to see aspects of the world better than anyone else for example these images in abled to him to see the Western us breaking up and evolving over time he has a 3d multi-channel image of a mid-ocean ridge now many of you might think okay why is that important well that enables us to see the structure of how the Earth's plates pull apart it actually adds a very scale in which these processes work so that basically means that we can see things better than we have before and tonight's talk is going to show how this image data processing and acquisition really gives us a new twist on the California shared zone so now without any further ado I'm going to ask Graham to talk this evening and he is a little worried that some of his wonderful technology he's brought here tonight would work but then Graham I'm sure it's going to go wonderfully many of you I suspect maybe some investor types looked at this the title and said I got to come here because there might be a lot of money to be had out in the Eastern California region but the title of my talk today is California in 10 million years beachfront property in the High Sierras that's really not my title that's what the aquarium turned my title into right the real title was I guess California really will fall into the ocean so with that hopefully in the next 45 minutes you will see how California will evolve the next 10 million years and again I'm willing to bet anyone the best bottle of wine we can show up over in Lone Pine but really the reason to understand this is that there are a lot of processes that are ongoing today along the Eastern Sierras that in some ways you will appreciate through the photos if you've ever been there but really there are also natural hazards such as earthquakes and tsunamis that can occur today within the High Sierra and they're related to this deeper seeded process so that's what I hope to show a little bit of tonight but for those investment types I just want to read this for you that except for the geological information contained here many of the matters discussed in this lecture are forward-looking statements that involve risks and uncertainties so this is a beautiful picture of in the bahia de los angeles-area of the gulf of california and this is one of the less beautiful pictures that one might see along the eastern corridors of the Sierra heading out towards Tonopah so I'll just give you a little outline in my talk and what I hope to to bring across one of the first things we'll do is just take a photo tour of this area for many of you that have not been to the Gulf of California eastern side of Sierras it is certainly one of the most pretty places on the planet and I've gotten some very famous photos from a number of people and the one thing I'll tell you is there were no color filters used there was no photoshopping this is really truly the way the land looks and for instance the High Sierra is also called the range of lights because it's just spectacular under certain lighting conditions the colors are just really surreal so I just thought we'd get a better appreciation of what we're looking at then we're going to step back about 60 70 million years and look what was going on with the California and subduction along the west coast and then go on to more modern drifting and something that you're probably not familiar with but by the end of the talk you will be the development of the Walker lane we're going to do some 3d fly throughs of some of the various data sets right and then we'll discuss a project that we've been working on for about six years here at Scripps and looking at the tsunami wave generation in Lake Tahoe and lastly we'll end with what we think the California may look like in ten million years but before we go through this series of pictures of this riff system I'm just going to talk about three different really types of faults that we study in this region you're probably certainly now most familiar with this type of subduction thrusting events this occurred obviously office' mantra well one plate is pushed under another and we now know the devastating consequences that's a thrusting or subduction type fault zone if I had a milky way with me I could pull the Milky Way apart and that would basically highlight extension or normal faulting we see a lot of that along the eastern edge of the Sierras and lastly we're all familiar with the San Andreas and that's more of a strike-slip fault like that so these are the three types of faults that really have shaped California or the California's both Baja and Alta over the past 60 million years but first I would like to just walk through some images of the Rift zone we're to start in Lake Tahoe and work our way down to Cabo San Lucas and again I would like to thank John Paul galleries and mountain light gallery and the late Galen Rowell for these some of these photos they're absolutely spectacular many of you are familiar with Lake Tahoe if you haven't been there please go it's absolutely lovely but it's no different really than the rift lakes of Africa in Africa were rifting older continent but in California we're rifting a younger Mesozoic or 60 70 million year old piece of continental crust so it's expression is different but it's really the same process that's going on and as you know Lake Tahoe's is renowned for its water clarity although it's it's stress at this point due to development now we're looking from the north towards the South Shore and again it's just beautiful beautiful clear water and this is certainly one of the prettiest pictures of Emerald Bay that I've ever seen this is the second most photographed area in the United States only Niagara Falls Kodak at Lisa ledges sees more photographs process and again this is probably not your average day sunrise over over Lake Tahoe and again we're going to head at the end of the talk and again Lake Tahoe is a rifted Basin with large normal faults underneath about 500 meters of water and that can cause a lot of problems as we head south towards a Mono Lake and this is the Lake Galen Rowell photo here and the tufa towers in Mono Lake as you're seeing one of the things we keep seeing are lakes and so even though we haven't quite developed the Gulf of California Sea of Cortez all the way up along the Eastern Sierra we do get these basins and they're kind of the tell-tale signs of what what's to come in the future and again this is a beautiful sunrise over Mono Lake and we had a little bit further south in a bishop area this is my favorite color picture I've ever seen in my life the the plants are not in the in the foreground are just surreal and again we're looking at one side of a rift where the normal fault essentially extension bounds up the Sierra Nevadas and they've been rising over the six seven eight million years and it's related to this rifting process lastly we head into the Gulf of California region and this is in the Loretto area and again beautiful area every every corner that u-turns just up it's just amazing again it's it's all speechless and lastly many of you are familiar with Los articles in the Cabo San Lucas area interestingly enough if you hang around these Granite's and then head across to Porto varta the southern part of town you can see the same outcrop essentially and that's area's been rifted about 700 kilometers apart so if you've been to enough of the beach communities in Mexico you can start to see the geology on either side of the rift but before that we'd like to do is just fly around this plate boundary and just get a sense of the larger geological picture so this is a global perspective of North America what we can do with a little bit of luck is fly in now we're applying there a lot quicker this time this is a perspective of the North American and Pacific plate boundary and as many of you know the rifting which started about 12 to 6 billion years ago in the Gulf of California there's a lot of small basins that are rifting apart and the last transform fault in fact is the San Andreas that hooks back up to the Mendocino triple Junction here so we're study this system as well as the rift that's essentially propagating in the backside of the Sierras that will come back out just north of the Mendocino fracture zone one of the things to realize over time certainly 60 70 million years ago the whole area that California's was was a subduction zone very much like Sumatra off Mexico Japan Chile and so there was active subduction very much like the Pacific Northwest but essentially all the way along the California's and and this plate that was subducting called a Farallon plate started the ridge started getting closer and closer to the subduction zone and that's a situation that's not very stable geologically and ultimately ended up in a this rifting event so I'm a switchback and this is a beautiful cartoon that dr. tiny hot water from University of California Santa Barbara just to highlight what subduction really is and what was going on during the Mesozoic or about 70 million years ago at the end of the dinosaur age essentially we have the Farallon plate being shoved underneath North America and of course we get heating and volcanism this is very similar to what you see in the Pacific Northwest this just as well could be Renier st. Helens hood three sisters but this the string of volcanoes went all the way down along the Sierras and down into Mexico and those volcanic that were not erupted that solidified are the granitic bath lists of the Sierras that we see today now continents also grow in this manner occasionally there will be another slice of continent or or an arc volcano and when it collides into this subduction zone Trench it just gets pasted this gets shoved onto the continent and that's how the western edge of the u.s. continent or North America grew through time just by reading out this these pieces of terrain volcanoes and continental crust that's very complicated so I have a different slide that might make it a little bit easier so this is the Farallon cafeteria this is courtesy of Jim Falls at UNR and essentially this is the subduction zone here and then the plates are coming over and here all the individual terrains pieces of continent volcanoes and they all get essentially stacked in or accreted onto the edge of the continents so that this is a much better way of showing well how the California continental crust was created and remember please do not stack trains to be appreciated again we're go ahead and look at this process a number of times through this movie loop and what we're going to see here is how this plate boundary interacted with the California's over the last 40 million years and we'll wait till it rewinds and starts over again but recall that we have simple subduction along the California's until the actual spreading Center impinged on to Baja California and during that process at about 12 million years down here rifting was initiated along the Gulf of California and the Sea of Cortez was formed as well as the San Andreas Fault and notice that Mendocino triple Junction here migrating to the north that will be an important part of the story so let's go through it one more time and really when these ridges get close to the subduction zone they actually die it's very hard to subducting and what we'll do now the next slide is just come in to the San Diego area and see what was happening just locally in our area and the interesting thing is in some ways since we have a San Diego State professor here that San Diego State and UC Santa Barbara boys kind of party schools right well they both have their origin back in time as we'll see what the next see Santa Barbara is very close to San Diego and then it was finally rotated out as part of the transverse rain I can say that because I'm a San Diego State alum one of the interesting things is at about six seven million years ago a number of faults began to develop to the east of the San Andreas again what what's really happening is that the Pacific plate and the North American plate are kind of grinding by each other these are big plates so they don't really care what's happening on the edges and they're just going to find the easiest way to break alright and because of this big Bo and the San Andreas you know in the LA region there's it just kind of kicks out by Palm Springs and comes around through mountain high and then back along the coast that's just not a very happy state for a fault it doesn't want to live that way it's going to try to straighten itself out over time what we find out about the plate boundaries and indeed it is starting to straighten itself out so the minute that will move back up about twelve million years ago there were san andreas like faults along the borderland of Baja California where the toast gob Rioja San Benito faults and these accommodate a lot of the slip between the Pacific plate and the North American plate when it finally jumped inboard and most of that plate motion was taken up in the Gulf of California this becomes a pretty peculiar geometry and so it's now starting to break itself to the north and this is the Garlock fault this is the Eastern California shear zone you might recognize landers and Hector minor earthquakes back in the 90s and this is the Owens Valley area which potentially was the largest earthquake recorded in the contiguous 48 States historically there's the Fort Tejon there's the Owens Valley 1872 and then there's in 1906 and depending on what textbook you look up one of the three of them are the largest of the three earthquakes in in the United States one of the other interesting things if you just look at volcanism for the last 15 million years and this happens to be focused in the northern Sierras you'll show you over the 15 million years there's volcanism everywhere but if we look in time we notice that it's much more distributed and as we count back in millions of years geologists like big numbers we can't deal with decades usually it will basically sweep back and that's responsible that's basically showing us two processes that are that are ongoing one of them it's just the rifting that started but more than that is that that trip that that plate that was being subducted it was being subducted but once the subduction stopped what happened to that plate and it just sits there and essentially peels back and it call it they call it delamination and as it peels back essentially hot material comes in behind it and that's where a lot of the volcanism is sourced many of you have looked at a map of the basin and range knows all these parallel ranges here and space in a range and you go that's a pretty interesting feature this is basically when that that plate peeled back away the hot material rushed in and lifted this area up and then this area got was very high and just the strength of the rocks wasn't able to hold it together and it basically starts to spread out under its own gravitational body forces and so this area of the basin arranges but is really showing us this this delamination uplift and then basically collapse under its own gravitational body forces the part that we're going to look more at for this talk is what's called the Walker lane and this is this shear zone along the eastern side of the Sierras and we can count down from Tahoe Honey Lake Tahoe Carson Valley Long Valley Owens Valley Indian Wells and this is the eastern California shear zone Mojave area and essentially for the last six million years plus the plate battery has been trying to abandon the San Andreas and break its way through the Walker lane and what I really like about this one projection from Jeff Unruh and it was published a few years ago in geology is this the first projection that really allows you to see just how crazy the San Andreas Fault is basically we're projecting so that the Sierra Nevada microplate essentially this whole part of the Sierra Nevadas in some of the great valley acts as just one solid plate there's no faults in it it's just it's almost like a beam and it's cruising off to the north in this projection and as you see as you come at the Gulf of California it would seem at least common sense it would be a lot easier to shear across this then to do this crazy jog through the San Andreas and then back around and remember this triple Junction overtime is going to continue to migrate along the coastline so we're just looking at a process that's been ongoing for six million years and over time less and less slip is going to occur on the San Andreas and some of the faults to both the west and a few the ones to the east and it's going to break its way through and we'll show you some evidence how that's going to happen and why we know that but I just thought this is a beautiful projection to see just if you were a child and you wanted to rip a piece of paper you're not going to rip it this way you're going to try to just rip it straight through it's a lot easier to do a straight tear than is crazy tear around this way now many of you may have heard about the magnitude 6 earthquake in Park Field in central California about four or five months ago in September this was an area where geophysicist and geologist said there's an earthquake every 30-some years so what did we do we went out and put instruments everywhere and did it happen in 30 years no in fact I think we could pretty much prevent earthquakes if we could put enough size models it finally came 14 years late but the reason we like parkfield is we pretty much lied through our teeth when we're teaching geology to the students because we talk about plates and how simple they are there's these little plates and they're all distinct and you draw lines on the chalkboard and pretty much you're lying because the earth and geology is so much more complicated but here is an example of an area where it's just simple this is the perfect plate boundary we're looking to the north now and here's paso robles to the north towards the Bay Area and this is the trace of the San Andreas right through the park field area and as we the thing I want you to remember this in your mind and we're going to go to Southern California in a few minutes and it's going to be a mess but in this area it's perfect and the big diamond that's red is the main shock the purple ones that are a little bit smaller are the aftershocks within about a day and then you'll see the earthquakes sense and they're going to basically map out the fall plane now look at this no we're talking about that perfect plate you can kind of spin around see how it just everything lines up on an edge and that's because this is one of the few perfect plate boundaries that we have this is not typical see how just lines up on an edge so this is something that we we like to teach but we don't see very often we kind of back up and looks like the coffee over there was pretty effective but now what we're going to do is we're going to run over to the imperfect plate boundary and we're going to look at Southern California where we are right now so we're now back in SoCal sweep away and back up just a little bit one of the things that you'll notice is unlike Parkfield these kind of copper lines showing fault lines there's just tons of them and we know that there's the San Andreas and the San Jacinto and the Elsinore fault we have the Rose Canyon fault just about a mile offshore here and then there's the Coronado bank's fault and the San Clemente fault there's a lot of faults that help basically translate the Pacific past North America it's not just on one fault and certainly in San California it's a pretty wide band these two faults up here are the Landers a series of earthquakes and Hector mine this is 92 and 99 there's also a nice it was the Halloween earthquake about five years ago on the San Jacinto fault and we're going to fly underneath and remember how edge-on the earthquakes were in central California well this is not the case here they're much more like clouds you don't really if I just rotate around we really don't see a plane they just look like clouds it's much more diffuse at best we kind of get a plane about right there now we're going to swing over towards and again we're going to map out this is part of the Eastern Eastern California shear zone Landers and Hector mine faults and they're too basically there's a series of decks rule or right lateral faults here's the garlic fault coming across Owens Valley Death Valley kick up there so again as the San Andreas becomes further abandoned by not only its its arcuate shape but this Mendocino triple Junction it's easier to break through and cut the crust this way okay and again it's when you do some tricks with tearing paper you know sometimes it goes where it wants to go not where you want it to go and this is the same idea except we're looking at a continental scale alright in the last thing and this little little fly through we're look at we're going to go ahead to the south and look at the Gulf of California and some of these results are from a experiment that we had back in 2002 where we were looking at the development of this rift zone and what's really neat about studying this rift zone is you can actually really study both sides of the rift if you can imagine if you're studying the Atlantic and you look at let's say Virginia you have to go all the way off to Africa and everything in between and then how do you line up those pieces so it's a lot easier to line up the various conjugate pieces in the Gulf of California and there's a any number of different data sets on land we have the local geology painted over the digital elevation maps and offshore we have both a global topography set and if we look closer we have Professor Peter Lonsdale is both imagery and this little Basin here called the alarcón Basin is really the first basin within the gulf of california where it started out as a continent and it rifted until more and more and stretch more and stretch more until finally you had ocean floor being created and we can see the abyssal Hills now in the Alarcon basin and if we rotate and look underneath we can look at our this case it's a velocity model just going to pop underneath whoops I'll back out a little bit we can see through it how about that not so much alright let's try one more time there we go kind of got it but this is basically looking in depth at crust in the a Lacombe Basin which is about six kilometers and then as you head further away it gets thicker and thicker and thicker and this is just a progressive thinning and thinning and stretching if I took that Milky Way and kept pulling it and pulling it and pulling it it would finally just thin down to the point where weeds just disappear essentially at that point what we've gone to is more of a conventional mid-ocean ridge all right so now the last part of the talk we're going to look at the Tahoe area which is really where we've been doing most of our research and so I think this is this whole process of rifting along the eastern side of the Sierras really didn't come into fashion until just the last few years one of the things we looked at was we knew that if you were I guess money was skiing over in over in Utah so when he was over at Alta and let's say I was skiing at Lake Tahoe we know that on average the two ski resorts separate by about one point two centimeters a year not that much every year right which is not a lot considering that San Andreas Fault slips about two to three times that but it's every year well what we mistakenly thought was that that slip was distributed across the entire Basin and Range because heck if you just look at it there's all these hills they go up and down and up and down and up and down and up and down until you hit this here so obviously you take this distance you divide by 1.2 and that's how the earth works well it wasn't what we found out was about two millimeters a year occurred right on the Wasatch Fault and from the Wasatch Fault until he almost got to the eastern front of the Sierras this was mostly just a push extended a little bit some pushed up a little bit and then boom once we hit this this region of the Walker Lane that's where we got basically ten of ten millimeters of the 12 millimeters of extension or slip in this very narrow zone now a lot of you have that GPS unit in your car right and that's a that's a cheap version of the GPS unit folks who have a lot more money can use a special GPS unit that's capable with all the processing of an accuracy of about a millimeter all right so they put all these GPS stations along the basin and range on this u.s. 50 transect you might have recognized that shape there and imagine that if I'm at the Alta and I move over to this station if we're basically locking step and we're not separating this arrow link is going to be zero and this is going to be just a TBD a little bit more that's how much I've moved if I move a lot further away that arrow becomes a lot bigger okay so as you see the arrows are not really that long until you finally get over to the Walker Lane and then they just bust out and what it's showing is by and large you're not really rifting or stretching this area too much until you hit the Walker Lane and then this stuff just goes crazy so right in this area the plates shifting up about ten millimeters a year and so that was something that we didn't know until about five years ago which coincidentally happened to be the time that we started looking at faulting in Lake Tahoe and this part of the talk is both to understand exactly how faulting works in the Lake Tahoe region and also realize that there's a hazard there that's a little bit peculiar and now you probably understand why by looking at all heightened to that awareness now after the Boxing Day tsunami and here's what you'd like to do if I have a fault that I want to study right and understand the history of earthquakes on that fault I'm going to big a big old trench this is actually on the smallest of the three faults in Lake Tahoe this is Gordon sites from San Diego State another money marshals - and we went up there this past summer and dug this trench it's about eight meters deep it's kind of scary and not very wide and what we do is we expose the history of the faulting namely that you tend to have layers and and when the layers are disrupted you can basically see an individual event earthquake event and so what you want to do is make a big deep cut and then look on the face of the wall and realize that there's all these different events and it's kind of like a puzzle always say it's a bit like CSI for for Rock jocks right it's a little bit that crime scene investigation but you're trying to back out and actually you can see all this coarse grain material here this is called a clue BL wedge and what happens is right when you get a rupture it might be two three meters about ten foot high just boom it's down ten ten feet and all the stuff during that movement and over the next few years all this rubble that was used to be sitting on top collapses into this wedge or Kalu vo wedge and this tells us how big the last earthquake was and then we go in and get carbon samples or other dating techniques and we can piece together a time history and what you want to do over time is understand when the last say five six seven eight nine ten earthquakes are or were and then and then understand their time history so you can forecast I didn't say predict you can forecast when the next earthquake is or will be and they've only really done that for about four or five faults in the United States like the San Jacinto San Andreas Wasatch Falls for example so in Tahoe we're trying to do that because when these faults rupture there's significant consequences but guess what but two major faults in the basin are underneath five hundred meters of water so I do not know very many back hoes they're capable of going to 500 meters and more importantly I can't hold my breath that long and so we're kind of stuck because think of this you have these very dangerous faults that are able to generate tsunamis but they're underwater so our conventional techniques don't work so that seems like a project that we should spend some time on and we started this in 99 and that was a year after the 1998 Papua New Guinea tsunami that killed about 2,500 people and at that time we thought hey now people understand how dangerous these things are and as we know now that was just kind of kind of fortunate what would happen in the future and this is you let you know that when you get involved these big projects there's people from all over the country and this is about 10 or 12 people that have been involved this project over the last five or six years now why is it important we loop through this movie a few times but this is a tsunami wave cruising across Lake Tahoe and this is the time in seconds right there it's it's 84 seconds 98 seconds 2 minutes so my god were across the lake in two minutes and we're gonna hit about three minutes here we'd hit incline village in about three minutes but what this this was modeled by dr. John Anderson and his student Glennon chinoe say and he's at UNR now used to work at Scripps as well and this is a magnitude 7 event along the West Tahoe Fault and about two and three-quarter meters average slip which you'll see is actually probably conservative and if you were looking at this depth scale and when we first started the tsunami realizing that if you saw those colors anywhere around the lake the peak wave heights were between 3 and 10 meters depending on whether you ruptured the West Tahoe or the state line fault and where you are versus all the bit symmetry and stuff now just to recall the highest wave heights that I've heard record for the Boxing Day tsunami near Banda Aceh were 14 meters the waves that destroyed in the sri lanka Phuket Island air we're 4 to 10 meters but closer to 4 meters so a garden-variety normal faulting event in Lake Tahoe basically can generate waves that are equivalent to what we saw on the on the Boxing Day event but just because I have a model doesn't mean it will happen right and so that's the real question does this does this happen every thousand years every 50,000 years every million years it's every million years it's like getting hit by a meteor so what if it happens every thousand years and that's a big deal because it may have not happened for a thousand years and so you're sitting on a time bomb so what we went out is to try to put real numbers on the slip rates of the faults and how often they reoccurred and so how do we do that and professor Neal Driscoll at in grd geological research division develop this system which always called it acoustic trencher it's really called a seismic chirp but the way I like to think of it is it's making that trench that you do in Paleo seismology but you make it with sound and so what we did here is took three different types of data this is the Scripps chirp this is if you got some moolah and you want to buy off-the-shelf technology and this is what they collected back in the 80s and 90s there's lots of this now believe it or not this is the same area off the coast of South Carolina so this is a lot of data old hunt tech boomer data it's it's yucky this stuff you almost starts getting a sense of what the geology is right but as it's a channel or I don't know but as you can see when you compare this picture with that picture it's kind of night and day the resolutions about a decimeter but somewhere around here so we're really starting to get to the level that's important for paleo seismology like we can start resolving individual events in the seismic data all right and and we can start really understanding geology and we'd like to say this is the difference between interpreting and guessing and knowing and so we were able to take this technology up to Lake Tahoe and do some really groundbreaking science with it and I think this under underscores one of the functions of Scripps and a few of the other oceanographic institutions is that we still develop instruments and it's through the instrument development that we can make breakthroughs you know a lot of companies use this and by this technology but they don't have really access to this until we develop the fourth panel and this becomes the standard off-the-shelf technology so that's again an important reminder why it's important for institutions like Scripps - to be around and here's here's this being deployed off of the RV Jean LeConte we work closely with a number of institutions as you saw including University of California Davis and Charles Goldman's group and I'll tell you it was a tough work for the last five or six years in Tahoe but somebody had to do it and unlike today within you knows plate the University fleet you can't swim call right guess what on the Jean LeConte when it gets hot and you're tired you get to jump into the water so that's always a pleasure but this instrument is different in a number of ways and it's the transducer array that makes the chirp sound it kind of goes eight times a second we can signal process that chirp into a very resolute wavelet and we also do all the digitization on the fish itself and believe it or not those two things are the difference between the middle panel and the top panel and we're now proposing to do the fourth panel where we're going to be able to the next step we're going to get down even further resolutions and this is what we need to do to further our science and now we're going to flip back over to Lake Tahoe and we're going to understand how we reconstructed the faults lip history in the Tahoe region if I can keep my flying under control all right this data was the bathymetric data that you see here was collected in 1998 by Jim James Gardner at the USGS and but we've integrated here in this what we call a visualization scene is about five or six different data types the deeper bathymetric data in the lake kind of from the yellows and greens down to these purples we're collected with typical sonar acoustic multi beam bathymetry the shallow areas however are collected with the lidar Lake Tahoe is clear enough that you can actually scan a laser through the water and get the shallowest levels of the lake in exquisite detail then on land this is your typical seven and a half minute quadrangle USGS digital elevation map which means if you've ever went backpacking on these things if you follow them too literally you could step off a cliff so you don't they're not the greatest Maps in the world but they'll do again what we do is collect these little acoustic trenches with the trip device now I want to back up and what we were talking about with this modeling a few minutes ago we're hypothetical ruptures along the west tahoe and state line faults and we'll fly around and look at these iskar or escarpments from the Falls remember if you see ground rupture on an earthquake especially a normal fault that means it's very large six low seven minimum so we're not in the case where okay you guys are exaggerating it's a whole bunch of magnitude for events and you're just making it bigger than it really is but in fact we know once we get these significant false curves that rupture the land that there Biggie's they don't make small the other interesting thing in talking about a really bad day is noses-- blocks here this one's not quite as big as Soledad Mount Soledad but it's kind of on the same order see this big block if you stare at this long enough it wants to creep up over here and this block creeps up there this little guy shoves in over here and you can play the game and realize that this this pile of little icebergs almost belong back in this McKinney Bay and the mccabe a reentrant and in fact about fifty thousand years ago this edge of Tahoe collapsed and generated this huge slide now the tsunami height from this event has been estimated to be a hundred meters okay so that's that's three hundred and some feet and that doesn't include run-up which certainly probably spilled over the top of the mountains there was an event in Latia Bay in the 50s by Glacier Bay were a similar sized earthquake earthquake triggered landslides generated now get ready for this a run-up of 1700 feet all right and took down trees that were like this big all right so this was a very bad day now this may happen again if you shake this Basin enough you can see these very steep sides over here by Rubicon over here by Crystal Bay it may be winning the Geo lottery it doesn't happen that often maybe every 50,000 years hundred thousand years but one has to realize that there is the potential of just an astronomical failure and devastation at Tahoe area that goes beyond anything that we can even comprehend but let's first step back from that and worry about the one that's more real realistic at least in the short-term and that's looking at the ruptures of these different normal faults so we're fly down to the state line fall right here and I'm going to look at this screen so I can fly we really liked about working in the Tahoe areas pretty pretty much every time we collected another profile we could stick it into a textbook because the geology was so straightforward here's the fault scarp which in and of itself was about 40-some feet high and if we drained all the water out there'd probably be a little sinus at the the great earthquake of 4000 BC was here right you know but it's again under 500 meters of water now remember that big catastrophic landslide about 50 thousand years ago well since that time and through a number of glacial episodes the lake setup just rained out suspension sediments and produced about twice a meter thick pile of sediments on top of this slide a little bit thinner on this top and here's the top sign guess what these two sides don't match they don't match because they cross the state line fall let's just rotate under a little bit now if I were to take my acoustic ruler out and measure from this point here to this point there it's 21 meters so we now know that in 50,000 years that this service has been split by anywhere from 21 to 25 meters that's a lot right that's not our only clue to what's going on if we fly back and look at the edge of Lake Tahoe if you're familiar head over towards Emerald Bay and Rubicon this is a profile that's showing us the tell-tale signs of an old Paleo shoreline terrace now a lot of you when you were kids or your kids today they get all filthy and they jump in a bathtub they play around and they jump out and then things kind of settle on the new drain and you leave a bathtub ring a very similar in lake tahoe area from about sixty thousand years till twenty thousand years the lake level was about fifteen meters lower and they just sat there in the wave action cut these beautiful benches out and then the lace the last glacial maximum came through raised the lake level up the channel filled in and while we have the current lake level but this surface was then preserved so every time this surface was intersected by a fault and then the fault would drop down to the east that was preserved it was no longer beveled off and so now we just encircle the lake and every time we cross the fault we get to see this bathtub ring or this old shoreline jump up as we go counterclockwise and so this is a real neat little trick and so if we look in this area on the west side and basically right very near the West Tahoe Fault this shoreline here is at 11 meters see that little limit right there that's about the distance for my son's Heinen to the floor about the height of your chair the seat of your chair this is very high resolution data and you can see how deform the sediments are in the past this area certainly was being affected by the westfall now we're a fly across the lake to cave rock and many of you have probably driven through cave Rock on your way to helping the casinos build larger buildings so we're cruising to Cairo and we're look at the shoreline on this side of the lake there we go here's the old erosional Terrace you can see how these beds are truncated off and then here's the modern Delta deposits prorating out on top of it and at this level right here it's 21 meters 410 meters so about three years ago we took a big barge 80-some foot barge and we rented a big old 40-foot crane and then we told you see people who self insure that this is what we're going to do and there were some high winds we almost lost the the whole kit and kaboodle so you know thanks you see many times we're not going to come back with our gear and they're going to be stuck with it but for now we were able to collect some very critical data and we were able to age date the surface at about nineteen thousand years kind of makes sense because that's when the glaciers were again big and if you're familiar with Valley that's when the Olympics were in 1960 but a big glacier came out abutted the the valley there and rose the lake with an ice dam so now if we're going to head back and we're going to fly down to the Ponderosa ranch I think a lot of you are familiar with that right Little Joe and Ben and Hoss right right outside their front doorstep believe it or not is another Terrace here this Terrace is at about 26 27 metres or another five meters deeper so envision this you're having a picnic with your family 20,000 years ago Emerald Bay and one of you decide to walk over to Incline Village and then you wait there for 20,000 years all right it's a long picnic day your family member will now be fifty feet lower or about 15 to 16 meters lower to the Northeast due to fault movement on the West Hall the state line and the incline village so you think about 50 feet your average rupture might be something on order of about 10 feet that takes a lot of large earthquakes to drop one shore line down 50 feet in 20,000 years and these are the tell-tale signs that there's very much earthquake activity in the Tahoe Basin and it's ongoing in fact we started to look around once we saw everything underneath the water we started looking above the water and again as a kid we used to drive through there and ask for parents to honk the horn through the cave at Cave Rock and in fact the cave @k rock that you drive through is man-made but right up here is a beautiful wave-cut cave and we knew there was a cave on the other side of the lake and they were likely formed when Lake Tahoe was a lot higher during Tahoe glaciation 60,000 years ago so we said hmm we know in 20,000 years it's 10 meters deeper or lower to the east so maybe in 60,000 years this cave should be about three times as much right and so what we did are about 30 meters so I had a student who under well unfortunately maybe that's not the right word but had to go over and fight in Iraq for a year so he came back to Scripps and we said well what should we do so we sent him skiing up in Lake Tahoe but said if you're going to get to ski you have to first go measure those caves and then you can ski so that was him react lamenting to a college life and and so Jeff went up there and lo and behold it was almost too good to be true it was twenty nine point seven meters between the different caves and so what does this all mean what's regards to the Tahoe area essentially we have three major fault zones two of which are underwater and they have slip rates that are slightly less than a millimeter per year along the west tahoe along the state line inclined village and this is where we basically you saw the trench rule earlier now if they basically rupture in a uniform manner like west tahoe goes and then a certain amount of time the state line goes and the west tahoe goes again equally spread out they don't have to be that way they can cluster together every 3,000 years you will get a tsunami that will be on the order that you saw model with wave heights from three to ten meters and so the real question now is uh is when was the last one that's what we're working on but it also demonstrates just how active the Tahoe Basin is and how it's being rifted apart and so it basically is a manifestation of what's going to happen for the next 10 million years and one of the reasons to do it of course and I did but I didn't show you what's that trench that we we dug was 30 feet from the incline village Elementary School which is a cinder block building with 600 kids a day literally built right on top of the incline village fault which you can't hold us to it looks like the last major event was about 600 years ago so that's that's kind of scary and but important also so what's California to look like in 10 million years well one of the things I hope is the menu gets a lot better because I I like the tacos de pescado and come-along carne asada right Theresa machaca much better and along with that new menu we're probably going to see something if Baja was any kind of as a guide what's going to happen with the San Andreas is over the next 10 million years you're going to see progressively more and more slip be transferred over to the Walker lane in a way again very analogous what happened to Baja and if this scenario which is more or less likely to happen and you'll accumulate about 500 kilometers of dextral slip and extension within the Walker lane and so depending on how the faults break you'll start developing these small basins like they did in the Gulf of California and once they kind of spread out enough they'll interconnect and what we'll see is the Sea of Cortez it's starting to extend up towards Tahoe and Honey Lake and it should be an interesting sight and unfortunately we're not going to be there but I think it does give us an appreciation for the beauty of the area and why you see these beautiful rifted mountains why on occasion you might see a volcanic event in Mammoth or why potentially there might even be a tsunami in Lake Tahoe or when the tsunami occurs you'll understand why that's occurring and again I'd like to thank you for coming on Valentine's Day and hope you get a little better appreciation for the California's and how they're going to evolve over the next 10 million years so thank you you
