Peter Betts - Monash University - Structural Geophysics

well welcome everyone to jayaharg happy friday so this week's rockstar is peter betts and his structural geophysicist in the school of earth atmosphere and environment at monash uni and he'll be chatting to us a day today about why a geologist thinks he's a geophysicist and geophysicist thinks he's a geologist so thank you so much for joining us this is his second time back i'm thrilled to have him he gave an excellent talk a few months back uh yeah about the crisis of geoscience which was amazing you should catch up if you haven't seen it but yes thank you so much pete for coming and yeah can't wait to hear from you hey thanks jess again um i'm just going to share my screen and just despite 15 months of only doing zoom i'm still sucking at it okay so jess asked me to come along and give a talk again um and i'm in the same environment as i was last time which is my bedroom um it's not as moody as laurence uh um study but it's uh it's yeah we're about to we're we're at a lockdown in in melbourne and what that really means for everyone is i mean there is the cage is slightly bigger it's uh it's not uh it's not really feeling much different so i'll look i've i'm gonna give a talk um it's called structural geophysicist why geologists think i'm a geophysicist and geophysicist think i'm a geologist and and um and hopefully you'll see how i landed there um so i could re-title that when i'm a geologist i don't understand the math and i'm a geophysicist but i don't know what the mineral is that's the other way and in some ways i have felt like i've laughed my way through two disciplines through my 30 years of being involved in in the academic um community and it is it is quite um it's quite interesting um to reflect on on your journey when when you don't really know what you are so i have two pieces of feedback that really early on i was eating in back in the early 1990s um and we had a professor called jim cull who was an electromagnetic athletic telerik expert and he was he was angling for me to become a geophysicist and i actually was thinking um along those lines um and when i chose to do an honest project with uh rick valente who some of you will have met a few weeks ago um when steve nickelway gave his talk um he said to me shame you do structural geology you would have made a good geophysicist and and two years later when i was doing my phd and it looked like i was uh not doing any more geophysics and i was becoming a more like a structural geologist or a geologist um my supervised time a guy called gordon lister said to me it's a pity you like geophysics because you would make a good structural joules and they're both very scarring uh quotes because actually it really showed that it wasn't really um um well i didn't know what i was really doing at the time i was kind of just flicking between the two of these disciplines and and fumbling my way around and i didn't think i was particularly who our duty goes back to that time probably wouldn't yet so there's rick he was the guy at monash university of the time he's now at uq who's sat in the middle of structural geology and geophysics along with a guy called mark jessel and uh and rick basically put me under his ring uh wing and um and and you know gave me project that was uh combining structural geology and and geophysics and and rick was a structural geologist by training and and started to um delve and and play with geophysics at the time of course rick can always look like that this is what he looked like in the halcyon days of my astrology um that's me when i was a redheaded and not crying and it's significantly thinner the guy in the middle is my brother who was uh who was my field assistant for a period of time and it was rick and and rick was a cracker in the field he uh he certainly made it a lot of fun so so this is my journey it's not color coded it's like when i thought i was a geophysicist and when i thought i was a a geologist and and before even before then i did a computer um survey back in 1987 in high school and um had to answer 100 questions that told me what job i wanted to do and the and it spanned out three jobs it's number one was a surveyor um number two was a geologist number three as a geophysicist and and i chose not to be a surveyor because the year before that i was a work experienced person with the town council in east gippsland where the pies are made and uh and the only job they gave me was to hold the stop sign like the lollipop lady or the all the lollipop guys that sit there with their with their sort of ass crack showing and uh and uh and do that anyway i hated it i was like you know as a as a as a 16 year old super board so i was like off to uni i go to be a geophysicist that's what i had in my head um and after failing first year maths now physics i uh i got told that i was never welcomed back into the school of physics ever again and they would pass me through and so i did another year of mathematics and then and then it was all all rocks after that and i majored in geology geophysics and at that point i was like i'm going to be a geophysicist and then before my phd what happened was i was supposed to do a part of a project that was the geophysics bit and rick wanted me to do that and uh and another guy from overseas from from wales um was supposed to do the geology bit and that kind of just never showed up and so at some point in the first six months of my phd rick said to me mate you're gonna have to do both and i was like okay and then so i pivoted uh that early on in my phd and basically started um mapping and then and so then i did two post docs one was in in mount isa after the my phd which is where i did my phd and then one was in the gala kratom and uh and for both of those times i was pretty much behaving like like a geologist and it wasn't only towards the end of the uh the post-secondary time did i start to re-engage um with geophysics again and i've basically had to learn um all the software etc again and and robin will be sniggering in the in the audience there because every time i can't use the software now i give him a call and say you met a handmaid and he and he always does so and he's a gene chemist which is actually even more embarrassing for me um and then and then after that i basically was employed as a bunch of contract lecturer and was asked to teach geophysics so basically from that point on i started to integrate the bone both of them into the way i thought about the world this of course led to lots of confusion with my colleagues so for almost all my career if i went and surveyed my uh good friends in my own school who should know what i do some of them say that i'm a geophysicist and some of them say i'm a geologist which is really interesting because even in 2018 which is 25 years into my career i still have colleagues asking me what i do so i do wear my failure to um to sell exactly what i do to my colleagues um as as a badge of honor and i like to keep them confused of course this led to all sorts of things um and this is now how i perceive myself in the world i feel like i can do two things reasonably well um and uh and so only by on the planet that i could find an analogy to was was was background okay so that's how i perceive myself as a result of all the confusion that led up to it um i do want to talk about interdisciplinary sciences the big word we use from fighter management at the university and i i think it gets misused a lot because um um what what um the university often means when they talk about interdisciplinary is actually talking about what they're really talking about is multi-disciplinary um so interdisciplinary science is really the approach um where we develop um process skills and concepts um of at least two disciplines at the same time so they've got to be intimately linked it's not like you um could throw you look at them try and solve a problem and you bring in a geochemist and a structural geologist and go i want you to tackle this together um to solve this problem that's a sort of approach the interdisciplinary approach is where the two disciplines that you're um combining are intimately intertwined now i think structural geophysics is is the one true example of this approach um in in in earth sciences of course most of our colleagues that float around in academia uh don't fit the multi-disciplinary or the interdisciplinary they are disciplined experts the system is set up in general so that they become that so most most of our colleagues are very good at one thing and in fact there's they're so expert at it there's only a few of them on the planet who have the same amount of expertise on that particular topic that they are and that's encouraged and that's how you get deep knowledge but um which is what we strive for in academia but the reality is some of the most challenging questions can't be resolved that way they actually either result need a multi-disciplinary or an interdisciplinary approach i think earth sciences as a as a broad family of um of um expertise naturally fits in the multi-disciplinary um category so if you think about um your work environment and when you have a problem and you might throw multiple methods at it you often throw um different disciplines out of so exploration might use a g chemist and g structural geologist um they might talk to each other but they don't intertwine what they're doing necessarily that well um so making a point um so why is structural geophysics um important well there's two points i really want to make in this slide um the top point is uh is basically uh one of which is images from about five or six years ago now when he did an analysis of you know where the big deposits are which is how big the bubble is and how um how deep they are and what's immediately apparent from from that image is that um there's lots of yellow and and even some white dots which means there's um lots of or deposits that we're really good at finding near the surface and as we get deeper the thoughts get the dark blue dots get fewer and we as a broad community are generally pretty poor at finding all deposits even at a at a modest death that's around 200 or greater um people will tell you their success stories olympic dam is one of them um and that's challenge so we need to use techniques that can see under underneath uh at depth so and and geophysics is one of those things and the other interesting thing about many autopsy is that they're structurally controlled um and so uh and so if you can combine um that those structural approaches with uh geophysical analysis then then you've got a a tool or a weapon to to apply that with um so i would argue that when you do a geophysical interpretation it's actually not just about making a map it's actually about making a structural map and trying to understand um and what those structures mean and uh and they have some advantage so um usually um we're talking about three dimensionality of uh rock um volumes um and structural geology deals with that as uh so um geophysics um i talk about the kinematics and i should be talking about the overprint as well and i've got another slide that outlines this um but if you can figure out the structural control and you can actually map those structures out at least you've got something to bridge with um so here's this how they can think and i kind of introduced it on the previous slides so these are the two these are like these and and boyd from south australia's three um people who were um who were um integral into into developing this um this this discipline that saw this interdisciplinary of sciences so mark's now professor uwa rick's a professor at uh uq um these guys when they were doing this were young men and they were um really playing on the edge of um techniques etc and and so so um so what i'm saying is is the three points i want to make here let me put my pointer on bear with me for a second the laser pointer so really um you know as if i put my structural geology hat on and when i can't understand the math and you go what is the purpose of a structural geologist they're really concerned with these three things 3d geometry determining the over-printing relationships which is actually the sequence of deformation events that leads to that three-dimensional geometry and then how did the rocks move when that was happening so the kinematics okay and so if you apply those three concepts to say gravity or arrow mag or other geophysical techniques they're exactly the same and that is why these two disciplines are interdisciplinary so there's this parity between the objectives of both that work really well and that means that you can apply the lessons from one discipline to the other and vice versa which is really um powerful unfortunately this doesn't always happen and so here's a here's a ford model that i've just stolen off mark um and and this is a typical approach i still see this approach today and it is uh uh and all this is is is the construction of some um some bodies which are colored blue and orange in this and they're given an arbitrary well they're given a rock property and then the geometry angle the rock property are changed until they get a satisfactory match between the um the observed geophysical response and the calculated one and so this sort of reductionist approach um is common and the argument is is there's so many uncertainties let's just make it as simple as possible to figure out what's going on and i would argue that neither of those two bodies floating around in rock space represent anything that would ever look like geology and so you end up with this sort of um approach that's not very um not very um geological and it's still applied today and it usually is applied by groups of geophysicists whose understanding of geology i would argue are limited but that misunderstanding goes the other way as well here's here's some cross sections that i drew in my phd and i didn't want to show you the location of them because it would just confuse things but basically the cross section is uh is the geologist's view of of of the world um and it's usually based on surface observations and then once you get more than under the surface it's a free-for-all and it's kind of made up um and and when you explain that to many geologists they get really offended by that um because but it actually is real so in this i'm going to use an example here so i've got a surface geology here yet somehow i've made this if this fire creek fault a into a normal fault and you're going to go well how can you tell that from those surface relationships there and the answer was i couldn't but so why did i draw it as a normal fault the example in this case is actually use some geophysics to help me draw that but if i had to just constrain it from the surface geology that relationship that's at depth would be um would not be not be able to be determined so so just drawing a geological cross-section is also um is is something that we uh is fraught with danger when we try to so i'm going to understand you this um series of um ford um models just to illustrate a point it's um from a phd student of mine more than a decade ago john stuart at the time i think he was producing some of the highest quality ford models um being published um these are crustal scale sections um through the western wall of craton um and uh i would argue that his approach was i want to draw a geological cross-section and i want to constrain it with my in this case his map which is his geophysical interpretation the magnetic and and and the gravity [Music] data and applied to that is um his conceptual and knowledge biases to that to that problem now you i've heard many people argue that they're they're pop that's problematic as well and and you can certainly make a case of that but now this is uh some this is a cross section in that's actually quite detailed in in in in its glory um that highlights and is self-consistent with the geological knowledge and the gravity and magnetic responses so we're actually using three data sets essentially to constrain that section and i only want to put that there to say that that's pretty much one of the approaches that we use in the strategy of physics group here's another example and this one's really interesting is taking blackie this is about csiro she was doing a uh well she's doing a short-term post off at the time this is this was her project the leica river fall trough which is in the western fold out of the mountains what is essentially a hundred percent our crop it's just it's some of the best outcome that you'll get in protozoa australia and yet um without um with with just the geological geological information you can come up with a with a cross-section that pretty much mimics the profile c2c prime in which is through here this section here goes roughly like that um and here's the forward model of that okay so they kind of look the same um but the the section that's been constrained by by this is is an example of um where you can get more or more accurate information in my opinion because this section not only honors the geology but it also honors the magnetic and the gravity data set so that's as an example i want to talk about the interpretation phase because that's the thing that i do most of the time you know i spent a lot of time drawing lines on well before i became in the university administrator drawing lines on onto physical um maps and i think the best interpreters that i've met have uh think like structured geologists um and and so in that process of creating that interpretation is constantly thinking about what's the three-dimensional geometry what's the kinematics and what's the over-printing relationship okay and then when you when you incorporate that structural and and or tectonic analysis as knowledge into the interpretation and modeling you're able to glean some information um from that so so the knowledge i would argue is the actual data so the data that you've got so the geophysical data the gravity the magnetic the mt the em data the geological observations and then on superimposed on that is some sort of understanding of what things look like in geology okay so some sort of archive a dewey system in the library for oh that's what a fold of rust belt would look like that's what an extensional basin the predictability of extensional base is that the sediments will generally be lower density than than the basement these are the sorts of things that if you bring that to you to the interpretation you'll get more out of the interpretation than otherwise here's some examples so this is megan's example that's the part of spectacular but to hear some you know what started obviously caroline was in the audience before and this is the social book that's what i'm only showing you these not as examples of of the interpretation but to really say you know here's his some interpretations and these are the things that we um this is the sort of approach that we would do so we look at those three elements geometry kinematics and over printing the advantage of these data sets is you can do it at a relatively small scale say mine mine or camp scale and you can blow this out to a quantitative scale and in a similar talk i can show examples across scales which i haven't done and then you can understand the movement pictures and the history and then you can make some sort of call on the tectonics so you can actually do it at multi scales which is super important so here's an example um one that i did a few years away though um i don't want to talk to you too much about these points but i do want to talk to this point um um about the advantages of making them and so whilst automation is great and i'm going to show you an example of automation later on which i think is going to be very breaking um and i'll and i'll stick with that into laurent's talk in a month's time the process of making a map in terms of your thinking has lots of merit and the reason why it is is because that cognitive activity of drawing the line and seeing how that line relates to another line in your head makes you think about the problem at a much deeper level than you would ever get if you just press the button and let an algorithm run something in the background and then you get the answer and there's something significant in that that is that will become always becoming less less common in the way we treat our data sets and that's something that we we need to be mindful of i believe because we will become lazy thinkers in the future if we rely completely on automative approaches and that's and that's actually a real real challenge okay so um and and with that thinking um is par part of that thinking sorry is the ability to understand the problem that you're trying to resolve with what you're doing so here's a different map as an example and and the scale of those those little dots with the numbers you can't read on it that's 10k okay so it's about 130 or 40k long and about about 100k wide okay and that and this interpretation represented a month's worth of interpretation for a company um i will not say any more about it than that that's the map and you can see it's basically a look at the details but you you you get a sense from that map that um there's a lot in it and you don't really get it because of the scala it is and if i zoom into one part of this and check this container there um it's it's constructive image i'm showing trends that's the interpretation of that and of course it's super busy drill strap and then that's the that's a zoom in again and there's the detail and level of detail of that that's to show the multi-scale mixture of it but also um to show that um you can glance at significant amount of information from these data sets and this particular business was um was interpretation was enhanced by um the large volume of uh drill hole data that help to constrain it and and basically the integration of those two data sets to do that um i'll talk about over printing um last year we published paper is significant and if you know what you're looking for you can get lots of information so this is the cameraman to trough in in south australia and you can see the folding through here so the layer the magnetic layers that are folded around and and and then you can see that um and there's a there's a there's one closure and there's another closure like this and you can see this this circular magnetic feature here which is a a granite it's a um an a-type granite and that's cambrian and age and it is over printing and and and truncating those um those fonts so you can get a sense of the sequence of deformations you have the folding event in this case and looking for details and then you had an igneous intrusion event that that essentially overprints it and you can see this fault here that's um truncating the limbs of both these folds there's uh there's a sequence of deformation there now there's no almost no outcrop there so you can see obviously why there would be some advantage to interpreting um a dance set like this because there's no other constraints to do it this is a leica river fall trough and which is 100 outcrop and and in the past we uh so laurent and i in particular who used to run this prac for third years this is the image that we used to give them and and they used to uh the students used to interpret this over about a four or five week period and we used to shake our heads at each other and go there's something not right about this uh the knowledge of this part of the world and and here is hearing lies the issue so you can see these these high magnetic zones through here here shown in the red these are the eastern creek volcanics which are at 780 million year old atholitic basaltic package um deposited in a rift and you can see if you follow them around they are folded around like this okay and then you can see over printing those limbs of those folds are these sort of wedge-shaped um packages of rocks and that's a they're sub-basins of a younger sedimentary package so so in in the before we started thinking and interrogating this data the story went like this that that these eastern creek volcanics were deposited and then these basins were um filled in with sediments and then these um fold formed during post basin history defamation and and so that was the paradigm and it went on this for probably 80 years the way um it was taught taught and and thought about in in the mount oscar when you look at this data you cannot get away from the fact that those basins are clearly overprinting that fold okay that's the overprinting relationship and so what the implication is is that big regional fall which is called the the leica anticline is actually happened between the deposition of these volcanic rocks and the deposition of the roxophilis basin okay and so that is a an event called we call the leicard event the details are not important except for to say that the macro geometry of the eastern western fold belt is actually largely driven by a folding event that's was largely unrecognized at this scale until then now there's a couple papers out there that allude or hint to the fact that there was a a basin inversion event between those two basin phases but i think when you look at the data at a holistic scale you get some sort of hints about what's going on so um i'm not going to talk to these points except for the same basically you can apply the skills and and knowledge that geologists apply every day of their life that they learn in first year which is what's secret events this event happened first and this one and you can apply to um to physical data set and you can get lots of information there it may not be apparent um necessarily on the ground and talk a bit about kinematics um which is really a way rocks move we have a whole bunch in structural geology we have a whole bunch of criteria used and we stiff around rocks at all sorts of scales uh looking for it the laundry list is there but really these these features um dominantly reflect the flow of rocks um and minerals are rare and rocks and minerals that are rigid that's essentially it some rocks are rigid and and so they rotate and and and other rocks will will flow and that's essentially what underpins that so here's here's an example of a folded uh dyke and there's a shield that goes through there and you can see this foliation bending around like this and this foliation bending around like that and uh and any structural jolters walk up there without thinking and get the movement of that we can also look at thin sections and here's some examples out of a textbook various um types of things where they're mental porphoblasts that have got tails on them whether they're sc fabrics or microfiche and we look at those features and we go that's how we can determine how a rocks move and those are observations that happen typically at well you can see the scale of the pen there so that's probably half a meter across maybe a bit more no sorry a meter it's a couple of meters across no one has it in that small um and these are these are sort of on the on the millimeter scale which presents challenges that have a larger scale and we usually rely um on minerals and um and and fabrics in rocks so sort of heterogeneous elements inside rocks to sort that out so here's some examples of similar looking structures in geophysics so here's an sd fabric that's taken out of the machine trowel textbook so these are that have got um um sort of an asymmetric uh closure to it so here's the central caller craton is a bunch of sheer bands that you can see through here that have got a magnetite missing from them so they're very clear and they're offsetting particular elements and truncating magnetic anomalies and you can see those same lenticular shapes just to the so that so that that example there is from there and if you just go to the north of that you've got these large um plutons and uh and they've got a highly asymmetrical shape to them there's one through here and here's another one through here and you can find an analogous structures in the microscale and so the good thing about this example is this uh this year the shear zone which goes across this actually outcrops there and where our crops is the kinematics are exactly identical to that predicted by that would be a worry if it wasn't okay and all we're looking at is flow of rocks around um rigid rigid bodies in this case here's another example in the muscular blocks one of my favorite examples because you've got um existing fabric in the rock and rotating it around inside into parallelism with these um shear zones that are very clear um and this fault here steps across into the manifold here and where it steps across is you see this subdued zone in the geophysical response and that subdued zone is actually where you have a series of um sub bases um filled with sediments that are that are um during the the magnetic response and that's happening in that in a releasing bin so the kinematics predicted through here um and the step over is creating a restraining event so that's an example of the analysis um this is just uh i really shouldn't talk to this because i even want to lose a little but i'll just say two things to this thing structural geology and structural geophysics are different in that the criteria that we use not the geometries um to understand it uh is that the sc fabric that i showed in the geophysics was a asymmetrical shaped um magnetic body so it could have been a layer or a dyke or something like that whereas you know you know in a sheer zone um in that in that in the um in the s fabric that is a recrystallization process that creates that particular shape so the geological processes that create those geometries are different but the geometries end up being the same and therefore you can interpret it in the same way so that's the only point i want to make and i'm sorry the second point i want to make is the advantage of doing it at the large scale into physics is you get the wholesale picture of what's going on which is important and you can do it under cover but all but the limit of this approach is that it works best for strikes that faults and it's more difficult to do the kinematics not impossible on on on on faults that have deep slip or or vertical movements i'm going to finish with geometry and then i'm going to talk about some of the processes and now we're going to slice so so um we have um fold interference pans so that's when super folds are superimposed on each other geometries most of us learn this in the second or third year in class um and uh and then forget about it but they uh they tell you this they tell you a lot they tell you stuff about the geometry and also the sequencing of events so you can even use the patterns um of the of um of of of fold interference patterns to determine um help you determine the history of rock so here's a here's a a a type three no type two sorry this is this is how it forms here this is so these are these three all linked together and what happens is you can have a recumbent fold and then you're overprinted by an upright fold and you end up creating these arrow head type geometries that reflect the interference between that recumbent fold generation and that upright fold generation and in the geophysics here you can see you can map this layer around like this and it comes in there creating that arrowhead and that one's in light and you can just make some sort of call about that now all i did in this case was when oh that looks like an arrowhead therefore it must be a type two fold and that must tell me that there's an over print between a recumbent fold and an upright fold that's the level of thinking here's the davenport province spectacular geology big dome structures similar to these sorts of patterns and these are really formed by two generations of profiles over printing each other so this is some sort of qualitative assessment that can be made on the rocks to tell you something about the geometry of course we don't we don't do that in structure physics we like to do more quantitative approaches i've talked about um talked about um four models so here's another example from alan aitkin's phd crystal scale model um we were looking at the uplift of the mojo through the muskrat block in this case um here's tk's phd her project was very much um interested in whether we could use geophysical data sets to map the relics uh of ma volcano explosion so a very different problem um and uh that's that's an example of her ford model so lots she went and collected her own data that's the data um distributed on on the volcanic signature and then she was able to map that out and then she used a series of frames of those four models to produce a 3d model like that so um i've showed you these ones so here's an example of the other type of model we do is inverse modeling which is uh we start with a priori model and and then we can um we can select the algorithm to to modify either the properties and the geometry depending or both until it gets a satisfactory fit and then we do historical modeling as well which is not really fashionable anymore but but it does help you with the learning process so here's an example from sharia armstead's honest project where she um had to model a geometry in the in the kunamona province in the larry domain and she had those arrowhead shape structures and she was able to model that geometry with uh an overprint of a series of recumbent folds that were verging southward and that and the interesting thing is with that um project was that everyone thought the recumbent folds in in mount eisenberg so that even that outcome itself was interesting we see a lot of inverse modeling happening happening in construction away and i'm going to this slide is really designed to show you why that's a idea um to be perfectly frank and lots of companies will tell you let's run an inverse model and they'll justify by saying that uh it's the simplest model to constrain the geophysical response and so this is from robbins who's in the audience uh phd um and and and this is a part of the mount painter block which is sort of way up in the northern part of the kerner motor province um in just next to the northern flinders ranges and it's really really really deformed and and and quite messed up and it's got overprints of igneous rocks and then it's got an autovision overprint on top of that and if you take the gravity data and you say on this on this volume of um crust here which is this is a surface expression and you say get a the best fit for this it will create something that looks like this okay which is really simple but makes no sense because it bears nothing towards the geology um this is a historical model that um that robin produced now you know it is exercising going insane to get a model that is this uh well constrained i think robin might verify that my understanding was 117 different events subtly changing the geometries to produce something which matched how robin viewed it was and then if you run a uh an inversion of something like that this is what the geometry would look like so look at the difference between that and that in terms of its um detail and and to be quite frank that's telling you nothing and that tells you a lot about that area now there's a story behind this one um and here's basically um how to do it now the joke is it's just to do this for the brave heart but basically start off with a series of information defenses up not all of them but you can see and and what what robin really did was he laid up the stratigraphy he deformed it with a particular wavelengths and then and then subtly modified elements of it to produce that and then just like uh intruded granted etc into it anyway so so the thinking behind all of this can be summarized in in this model and and and this is kind of uh us a loose summary of the way we would think about it in the structured physical group we'd start with saying that and that could be a geological map it could also be a geophysical interpretation it's basically a surface um yeah a representation a horizontal representation of what's going on we might put forward models in which are constrained by rock properties and then use those four models to produce uh helping produce an explicit 3d model we can also take the map and produce an implicit one or we can do this historical modeling and this we have we at the end of the journey we come up with one model which is what we call the our priority model that's the starting point and then we would apply um inversions to it which would use our properties again and then we would loop it around normally we'd make multiple models and loop it around multiple times changing the geometry of the rock property until we've got a satisfactory fit okay and um and then on top of that which i'm going to talk a bit is is uh um some more newly developed um bayesian approaches that um that are coming while they're here so here's uh here's the example of the case study in in robert's phd i'd like to add that robin is uh his expertise is in hostage chemistry so he's the most skilled um multi-disciplinary interdisciplinary scientist that i don't know so that's that's your plug for the year okay so um but a truly amazing piece of work this is how we started it basically took the data built this model that was designed to um designed to uh try and represent the 3d volume of of the complex geology that he actually physically went out there and measured and then he did this complex um process which i'm i'm not really going to talk to exceptionally it's a more complicated version of the uh process that i i showed before so basically you created um your priory model and then run a series of versions um systematically changing the property of the rock properties and all the geometries and i think the method he alternated so he made one inversion where the properties were changed and then run the next version where the geometry was changed and kept alternating that until we got a uh a good um fit um and one of the one of the challenges of that model was in the gravity we always had this uh this uh um this deep low here and no matter um how far we modeled um this using this interpreted geometry it never really um landed a satisfactory fit so the rms was always um uh their way out in in that part of the of the model so that's interesting because if you can't get gravity to fit it's telling you something that's fundamentally flawed with the model which forced um um robin to go away and think about what was it what element was he's missing so he ran a series of other um models to see if he did it and and to cut to the chase um the model he ended up landing with required an intrusion of uh of this sort of scale and volume um to be in place to get that um a good match between the um the observed gravity and and and that model gravity sorry so this this model here is this volume here and this model here is is the obs is it is the observed so he's had to go away and think about it and and come up with a a different model so that's the original model and that's the model that he had to use in the end so there is certainly um a merit in going away and running these models okay so that's the case study so i'm going to talk briefly about the barriers for interdisciplinary science and uh and there are many um and and so and especially structural geophysics so here's a here's another quote this is about the market who was college in his past at the same time with me you know and he's now he's now sort of a a broker and uh wealthy in canada but he used to look like that so um but when he was running our frontier group in the in the 2000s i caught up with him and he uh he said to me um after around some yamcha in vancouver i was asking what he was doing where he was exploring and what was going on and he said i'm so frustrated i said he goes i i'm so tired of handing out 100 grand a year to graduates and i send them out in the field and then they come back after six weeks and they show me nothing there's there's he said they're too scared to put a piece of line on the paper and i said so where's your frustration he goes well the problem is i don't care if the line's right or wrong but without that line i have nothing to work with in my decision-making process and so i walked away from that conversation going the yamcha was delicious but but actually it got me really thinking about um why why were why were graduates reluctant to draw a line on a map or a geophysical image and it and it really is confidence thing but you know they went out there and they went i'm too afraid to get it wrong and that and and that actually is something that that when you sit in the classroom you also said that yeah you said an assignment they have to draw some lines and some images and the first two hours they sit there um the students sit there and stun silence and make zero progress and it's not until you actually draw a line one line for them do they does it take off and so there's this sort of um stasis in thinking because there there's a fear of getting it wrong um that stops them from doing anything so what's the challenge of the intimate dismissal as i said i think it's confidence and knowledge um and that knowledge and confidence are intimately linked um and it's also a language barrier for geologists it is often where do i start what line do i wrong firsthand what's word to it and then it's about the the language and the knowledge about what are you looking at so there's a data that's um there in the in the top now i've looked at and i can tell you that just from its um texture and its color scheme that's tilt derivative of an image right but you know you say i know what that means whereas a a geologist if the geophysicist has an image says here's a analytical signal or here's a tilt derivative or here's a vertical derivative if it's a it's gold body greek to them and so there's a sort of you know what am i looking at and how am i going to deal with this right and then of course the jeff is wants to make it look pretty slippery shadows on it and do all sorts of crazy stuff it actually makes the image uninterpretable okay so that's the sort of stuff that um that fundamentally goes wrong so those shades are great if you want to use it as an image to show what the image looks like but it's not great to interpret so understanding how the data's processed and what that process data tells you about the rocks is also significant and that knowledge is fundamentally like there is a one of those word word images that graduates have filled out and the number one biggest thing that they say that they wish they had to learn in their undergraduate is how to interpret and model geophysical data because they use it on a daily basis in their jobs yet it doesn't usually get taught and then the third challenge for a geologist is how do you take a physical property of the earth in this case it's the make distribution of magnetite in the upper crust essentially and then convert it into something that's geological and that's a big challenge it's a big thought process so i look at an image and go oh that's a granite or that's a plutonium that's a fold or that you know because i've got this armory of experience but if you're just starting out you're going i don't know what that is it's a blob and so that's the challenge but you know and the challenge for jeff is not knowing enough geology fundamentally you know at the end of the day that's what we're looking at and so i would argue is how do you interpret something if you have no idea what it would even look like so that's why if you let the geophysics community go health the leather at a geophysical image you don't get often get something that looks very geological and different types of rocks are ambiguous and that's as well so we often get the same type of rock we'll give the same geophysical expression because it's got no magnetite in it as an example so this is the sort of um plunges that we face so i'm going to go back to this figure and i'm going to tell you about the time frames that it takes to do this right so to make uh into x weeks to build the ford models depending how good you are or how easy they are today's two weeks and then the inverse models the days two weeks and historic models of days two months that's robin and then we run the inversions and then take taste a week so the whole process to start from you know nothing to 3d volume that's geophysically constrained the structural geology can be weeks to months it's and it's labor intensive okay there's few groups on the planet that i believe can go from the start of that to the end of that process pg g science is one of them okay so you know they've got the skill set to do that but it is labor intensive so i've got two more slides to give you three more starts and i'll stop so loop is a project that i am loosely affiliated with and laurent is the ladies and the audience he is the leader of it and he is a was he was a cocaine expert wasn't a great expert he is and uh he fundamentally realized that um was we weren't doing 3d modeling um very well and uh and so he and his collaborators and still all down there it's mainly the geological surveys and some of the big companies who are really interested in what loop is and and basically loop is an integrated process where we take managed data and then we try and build 3d models that are constrained by the that knowledge plus geological information and geophysics at the same time so that's the that's the goal so rather than going let's do the geology and then let's do the geophysics and let's come up with an answer it's like let's do the geology and then and feed the geophysics in and it's all bayesian approach and then with that is uncertainty so it's open source software so at the end of this journey there will be a product out for the community um that will be accessible but the power of this is amazing so i'm going to give you one example of it which is this so here's a geological move of uh offensive ranges and all those little red dots uh structural points and you feed that information into the loop software and in 15 minutes you end up with a first uh first pass three-dimensional model of the geology so all that which all that work was taking weeks and weeks and weeks to do is now because this software gonna revolutionize the time that we do it and you know and the advantage of this approach is that you can run many many hundreds to thousands of models and find families of them so um that's that's not a supercomputer either in 15 minutes or whatever it's done on um laurent's shitty dell position um laptop that you can buy um over the shelf so amazing hey so this is this is the future of of uh of where where this is all going so this is the plug for loop and i know that laurent is talking about this project in details in one month's time is that right chess maybe the end of august i think it is so maybe two months yeah and and you should go and absolutely see this one because it will blow you away okay so last slide so potential for geophysical data set is great for all sorts of analysis multi-scale tectonics structural analysis because it basically informs three-dimensional geometry kinematics and overprinting not this really in that order um the second point really talks to importing uh importing knowledge which is data and and what you understand how the work world works um the workflow that we use i gave that really generalized workflow but how we set up our workflow is is really related to the problem and that includes the interpretation and and the style of modeling that you do and we would never even consider to consider in our group to do an unconstrained inversion um unless we wanted to show someone how rubbish it is which is the only reason why that unconstrained version was ever produced um i think there's about to be a revolution in in structural geophysics with some of that automation of maps and uh and integrated 3d models that will bring in is part of the process the geophysical analysis so the geophysics is actually part of that 3d modeling capability but i you know the one caveat which i made a point of earlier is i think we have to be very mindful that once we start pressing buttons and asking software to build stuff for us that we don't think that's replacing thinking about the problem and i'm going to stop there