Active Tectonics - Science topic

Dear Atul Singh many thanks for posting this important technical question which is certainly of broad general interest to many other RG members. In addition to the useful links which have already been suggested, I recommend thet you also search the "Questions" section of RG to find questions about the same topic. For example, please have a look at the answers given to the following closely related question which has been posted earlier on RG:

(29 answers)

Good luck with your work and best wishes!

Hello dear;

I didn't research on Paleomagnetic studies, but i know 2 methods in order to behavioral study between two things. K-means clustering and Artificial Neural Network (ANN). you can read this combination method in this paper :

good luck

Dear Ahmed Morad: I understand perfectly what is your proposal. The best way to show how marine sediments get into a subduction zone is to draw a detail of the hinge zone where the oceanic plate bends when foundering inside the mantle. In this hinge zone stretching occurs, and some expansive graben structures are formed (normal faults parallel to the trench), which trap sediments and lead them to subduction. Then those sediments are metamorphosed under high P/T conditions and become phyllites and schists, usually white schists, and even metacherts and fine grained marbles. There is a quite accesible outcrop in a main freeway near the city of Puerto Cabello (north-central Venezuela) of eclogite knockers inside a relatively monotonous micaschist. A close look at thin sections of this schist shows the presence of kyanite, garnet, white mica, and Mg-glaucophane, these are usually called white schists, since the glaucophane is almost colorless and retrogradly altered to talc! Some have carbonate too, and in nearby localities of this same high P terrane there are also metacherts and marbles. So, there's no doubt that some marine sediments are indeed subducted and transformed to high P metamorphic rocks in the subduction complex. Regards, Sebastian.

Try to see the following publication: Magmatic cycles pace tectonic and morphological expression of rifting (Afar depression, Ethiopia)S. Medynski, Raphaël Pik, Pete Burnard, S Dumont, Raphael Grandin, Alice Williams, Pierre-Henri Blard, Irene Schimmelpfennig, C Vye-Brown, Lyderic France, et al.

REQUEST:

Dear colleagues and friends, I need seismic reflection data for processing in a free software for master students. if there is someone who has some data, please send them.

Thank you for your helps

Lots of earthquake stations today, therefore, lots of data to study using the velocity of the waves. Scientists know a lot more information than previously and there is more to study. The data displayed in the lecture suggested by Dr. @ Borko Bulajic are amazing!

To answer your questions you need to first make interferograms from SAR acquisitions.

So say you have interferograms from scenes captured before and after an earthquake, and you unwrap the interferogram, you essentially have a map of surface displacement caused by the earthquake (with resolution depending on how coherent pixels on the ground are). Now, that allows you to easily invert for coseismic slip distribution on a fault in 3D. But these are only static offsets. You cannot investigate the rupture process with InSAR.

Now, the more fun parts are while dealing with other quasi-static processes like interseismic and post seismic velocity fields (and possible debris flow/landslides). If you collect enough SAR scenes over a particular frame on the ground, you can create a time series of the surface velocity field. Now you can invert that data for slip rates/locking depth of faults/frictional parameters/strain rates (for afterslip/visco-elastic relaxation studies). 

The links that have been provided by some of the other responses to this thread are excellent, and should give you a more detailed description of the possibilities with SAR interferometry.

It has come to my understanding.

Bedrock landslides (rockfall, rock avalanche) are found to be more sensitive to the change in area and hence their scaling exponent lie close to self similar exponent (1.5). Therefore, s can be considered to be controlled by size in this case. 

In case of debris (rock+soil) slides, varied material is found to be less effective to change in area and hence lies far below self similar exponent (1.5). Thus, in this case, material controls exponent.

However, a common relationship still seems rare.

I said yes for knowing subsurface conditions and structure using earthquake data. I didn't say for prediction of earthquakes .. otherwise your question is completely wrong.

Dear Najib,

In fact, i have noticed that the historical earthquakes were not accurately matching the epicenter and the magnitude. Our historical events are not well studied. From my experience with Syrian seismicity analysis i found that the earthquake locations were mapped incorrectly and their magnitudes were risen higher than it was. Yes nobody knows exactly what happened in the past, but i am sure that the seismicity in Syria, Lebanon, Jordan and Palestine was not much strong than as it is reported by many scientists.

Based on my new published model for seismic hazard model, the expected Maximum Mmax will not be more than 7.6 in Syria for 2% probability of exceedance.

When we focus only on historical events we 100% get higher Mmax, but we should look on both instrumental and historical seismicity at same time.

I am the one who studied seismicity and prepared seimic hazard maps for syrian territory using porbabilistic approach, i found higher estimates of Mmax and earthquake hazard.

Based on this appraoch, I found that northern part of Dead Sea Fault System (syrian segment) can produce earthquake with magnitude 8 - 8.3. From my opinion, it is so high magnitude which may never happen, that is why i tried to create seismic hazard map in different way.

In the new seismic hazard model, i got surprising and promising results. Recently, i compared the occurred earthquakes of 2016 and 2017 with the pridected values. The comparison show very close matching observed and predicted results.

Obviously, we need to improve our ideas and thoughts. We can't trust the paleo and archeo seismicity alone.

If the cluster is related to the same source, reasonably limited in area and time, it may be useful to work out a "composite focal mechanism" giving one mechanism for all strictly related events. This procedure helps reducing location errors ( particularly, the rather difficult to constrain depth in certain situations where the stations distribution or velocity models are not optimal). The depth factor has a great influence on the focal mechanism, it may radically change its significance and nature, hence yields the whole spectrum of erroneous other estimated parameters. For an example of a composite focal mechanism,see Abou Karaki N., Dorbath L., Haessler H., 1993, La Crise sismique du golfe d’Aqaba de 1983 : Implications tectoniques. C.R. Acad. Sci. Paris, t.317, Série II, 1411-1416.(In French + Abreged English version). and Abou Karaki N.,1995, Re-evaluating the seismicity of the Jordan Dead Sea Transform System, Proc. of the Fifth Jord. Geol. Conf. and the third Geol. Conf. on the Middle east GEOCOME III, Amman 3-5 Oct. 1994, 373-396. Full text available for both on Researchgate.

At least the magnitude of the main shock itself is the upper limit of the magnitude of aftershocks.

Hi,

I would suggest our paper: http://www.sciencedirect.com/science/article/pii/S0277379113003053

which suggests a new method to investigate Late Quaternary palaeoshorelines. This method, that we called "synchronous correlations method", takes advantage of the fact that (i) sea-level highstands are not evenly-spaced in time, yet must correlate with palaeoshorelines that are commonly not evenly-spaced in elevation, and (ii) that older terraces may be destroyed and/or overprinted by younger highstands, so that the next higher or lower palaeoshoreline does not necessarily correlate with the next older or younger sea-level highstand. 

If you have any comments, suggestions, etc., feel free to contact me.

Bye

Yes, it should be possible - if you have 3 independent components of observation you can derive the full 3D displacement. You can first write out the InSAR LOS unit vector with its EW, NS, and vertical components, and then solve for the vertical component in terms of the others. Insert the LOS, EW and NS observations into your equation, and you can get the vertical displacement. Note that all the LOS unit vector coefficients are spatially dependent, so you will have to do it for each pixel separately. If you have even more observations, then you can do it in a least squares sense to help minimize the error.

Hi Cyril,

A fine-blade diamond saw is your best option. Use plenty of water like Habib says.

Good luck, Ian

Dear Professors, 

I'm sure that these zircons come from sedimentary rocks according to other evidence. My question  in fact lies in that I don't know whether the angular shape is caused by the short-distance transportation or mechanical crushing during the zircon separation.I am sorry for the ambiguity of the question .

- Here you can find models of the different subduction areas, in these models you can see that  in general in South America subduction is steeper than north america subduction (cascadia). 

Subduction varies with time and it is related to thermal state of the overriding both on slab geometry and the resulting pattern of mantle flow.

For example, flat or low-angle subduction is related to cold lithosphere in North America, while subduction high angle relates to the warmer plate lithosphere Caribbean.

You can find more info in the  Rodriguez 2013  PhD thesis:

In Nazca plate there are large variations of dip angles (Pedraza et al 2007).

Hi

The vitrinite reflectance shows that the coals may have been formed at a depth and lately uplifted to a shallower depth.

Siddhartha,

The answer to you question can be found at: https://www.researchgate.net/publication/264825668_Plate_Tectonics_Driving_Mechanisms_Some_Simple_Rules_that_Explain_Why_the_Plates_Move_the_Way_They_Do

I would be happy to answer any questions you might have.

- Chris Scotese

Hi Patrice,

I would suggest tracking down the specific subduction zone ground motion models you would like to use and request a copy of the published paper that documents all the equations and parameters. It is then a matter of converting this information in Matlab code and doing some test data.

I would suggest the use of Atkinson-Boore (2003) Wordlwide Interface/Intraslab/Subduction ground motion models for use with your subduction sources.

You should find this link useful for NGA-2 West GMMs:

Also just a comment about your use of the term "GMPE" that term should really not be used, in my experience as seismologist, this would assume that the models/equations can predict earthquakes, which they cannot. A better term, slowly being adopted by (even) our peers is ground motion models.

Good luck!

Pablo,

Your is a primary question in earth sciences and I think that it is rather difficult, or even impossible, to reply with a more or less composite answer, since, as evidenced also by David, several constraints should be considered before trying to reply to your question.

And, first of all, I guess that you should take into consideration whole lithosphere extension, and not simply “crustal stretching”, and the evidence that slow-ultraslow rift systems are characterized by magmatic activity that is stored into the shallow mantle lithosphere without giving rise to subaerial volcanic activity.

But to obtain appropriated answers, the question should be posed with more precision. In fact, you write of “decompression melting (of the upwelling asthenosphere?) and recall that “such decompression results from the crustal stretching related with rifting”. Are you referring to a mechanism of passive rifting (driven by far field tectonic forces) with almost passive asthenosphere upwelling, without any active upwelling of deep/hot asthenosphere, as it happens in the case of asthenosphere diapirs or mantle plumes?

Your question (“how much of this crustal extension is needed for triggering the magmatic activity observed in rift settings”) is apparently simple, but it is solely posed in an oversimplified way. It needs that the estimates evidenced by David and, moreover, the driving forces of rifting and the geodynamic context are constrained.

Rift formation has long been the focus of attention for researchers, and an enormous number of studies have been carried out in order to understand causes and modes of whole lithospheric extension (e.g., Brun, 1999; Corti et al., 2003; Dewey and Hancock, 1987; Illies, 1981; Keen et al., 1987; Khain, 1992; Morgan and Baker, 1983; Neugebauer, 1983; Neumann and Ramberg, 1978; Palmason,1982; Ruppel, 1995; Whitmarsh et al., 2001; Ziegler, 1992; and many others).

Just as an example suggested by my personal experience, I can recall that in the case of passive rifting (where asthenosphere is considered to play no active role in passive lithosphere extension) experimental investigations evidenced that the lithosphere must be thinned to about half of its original thickness (i.e., thinned by a factor β≃2: Foucher et al., 1982; Corti et al., 2007; Ranalli et al., 2007) (considering a lithosphere away from mid-ocean ridges, mantle plumes and subduction settings), in order that the near-adiabatically upwelling asthenosphere undergo decompression melting under spinel-peridotite facies conditions.

FOUCHER, J.P., LE PICHON, X., SIBUET, J.C., ROBERTS, D.G., CHENET, P.Y., BALLY, A.W., OXBURGH, E.R., KENT, P., DEWEY, J.F., BOTT, M.H.P., JACKSON, J.A., OSMASTON, M.F. & TURCOTTE, D.L., 1982. The Ocean-Continent Transition in the Uniform Lithospheric Stretching Model: Role of Partial Melting in the Mantle [and Discussion]. Philosophical Transactions of the Royal Society A, 305, 27-43.

CORTI, G., BONINI, M., INNOCENTI, F., MANETTI, P., PICCARDO, G.B. & RANALLI, G., 2007. Experimental models of extension of continental lithosphere weakened by percolation of asthenospheric melts. Journal of Geodynamics, 43, 465-483.

RANALLI, G., PICCARDO, G.B. & CORONA-CHAVEZ, P., 2007. Softening of the subcontinental lithospheric mantle by asthenosphere melts and the continental extension/oceanic spreading transition. Journal of Geodynamics, 43, 450-464.

In conclusion, my suggestion is that you have to explore fundamental references on rifting, easily found in the international bibliography, and try to make your own understanding of the primary process you are interested in, on the basis of a good knowledge of the present state of art of researches on rifting.

Ciao

Giovanni

Caro Alessandro,

to my knowledge there are no papers that specifically focus on the cross-over frequency between a deterministic and a stochastic modeling. In our paper on hybrid modeling of L'Aquila earthquake ground motions published on JGR (that you can find on my page):

"Complexity of theMw6.3 2009 L’Aquila (central Italy) earthquake: 2. Broadband strong motion modeling"

we discussed about this issue in Section 7. You can find some relevant references there.

I hope you find this of some help.

Ciao

Gabriele

Hi Archana... while this is not my area of expertise, I do know that the Mediterranean Sea is closing between the north moving African plate and the European plate.  The Atlantic Ocean is opening wider at the mid-Atlantic ridge and the Pacific plate is subducting beneath the Asian and Australian Plates. The Australian and African plates are spreading making the Indian Ocean larger.

Hi

Please see www.stereo.net.au/forums/

Dear Phan,

It is very difficult to say from a seismic profile alone if a fault is active or not.  If your are is not tectonically very active, you can only determine this in two ways in my opinion.  You will have to investigate the earthquake seismology for your area of investigation to see if there are any recent locations of events that coincide with your fault location, OR you would have to open it up and investigate to see if you could find any neo-tectonic evidence.  You could also drill the fault, study the core for that and try to date the material, that will place an approximate age of the faulting.

However, the seismicity, and even the micro seismicity is the best and cheapest.  If you can, deploy a few mobile stations in the area for 3-6 months or so, and hope for the best that there will be some movement that will indicate micro-seismicity.  Then you will know for sure.

Hope this helps.

Regards

Stoffel 

Dear Alessandro, (dear all)

It is very easy after the earthquake occurrence to find that there was some kind of acceleration before it, especially when the earthquake is anticipated by a seismic sequence of small/intermediate shocks. From this perspective a simple answer could be: yes, L'Aquila showed some sort of seismic acceleration although it looked as evolving as a chaotic process (see for example my article:

http://www.sciencedirect.com/science/article/pii/S0040195110004270 ).

On the other hand, when some sequence is evolving, the problem to understand what is going on is also related to which data to use (e.g. instantaneous or cumulative strain or moment release or other real or pseudo physical quantities) and how to handle them in order to eventually identify an acceleration. Literature is full of great examples, and only very few exceptions were published before the earthquake really happened.

My opinion agrees with many (e.g Massimo and Ian above) i.e. that the problem is very complex and difficult to cope with. To what previously said I would add that we really need to analyse as many kinds of data as possible in order to establish with some confidence that something unusual is happenning. (Of course it will not be only question of amount of data but also of their quality). For this reason, I would prefer to change the question to: what was the physics underlying the L'Aquila seismic sequence (or any other) that brought it to culminate with the mainshock of the 6 April, 2009?

Although still controversial, it will be of great help also to identify possible anomalies due to the eventual lithosphere-atmosphere-ionosphere coupling that seems oto provide some typical manifestations, for instance, in the form of thermal atmospheric anomalies (e.g. see my article about the 2012 Emilia earthquake:

http://www.annalsofgeophysics.eu/index.php/annals/article/view/6123 )

or ionospheric anomalies (e.g. see my article:

http://www.ann-geophys.net/32/187/2014/angeo-32-187-2014.html about two Chinese earthquakes).

In particular that the problem is complex and difficult can be deduced from the results of the latter article where we show that ionospheric anomalies do not always appear, because the conditions to occur are not simple, depending on the solar magnetic activity, magnetic latitude, lithospheric conditions and, likely, kind of fault mechanism, sufficient energy of coupling, etcetera.

Although statistical analysis is important to grasp something of the question, I believe we need of something more "physics-oriented" to identify those fore-patterns that eventually preceed a large earthquake.

The centennial catalogue has been recently superseded by the Global Earthquake Model / International Seismological Centre Instrumental Earthquake Catalogue (1900-2009):

The authors of the Centennial Catalogue (Engdahl and Villaseñor) are coauthors of this updated and more complete GEM/ISC version:

This catalogue is mostly based on an extensive dataset of phase picks collected from a large number of historical bulletins. A overall analysis of the catalogue completeness in included in the publication above. Also, Andrew J. Michael (USGS) presented some other results about the catalogue completeness in the AGU Fall Meeting 2013:

If you are interested in the instrumentation, operation dates, etc. of the stations used, I would contact directly the catalogue authors. However, analyzing this vast amount of information seems a cumbersome task.

Best regards,

Álvaro

I think you mean sliver plate (not silver). It is a small plate, generally much longer than it is wide (hence a sliver), wedged between major plates, as a result of strain partitioning. For example, oblique strain at a convergent boundary between two major plates often gets partioned into a component normal to the boundary (leading to pure thrusting), and a component transverse to it, leading to strike slip deformation. If these different directions occur along major plate bounding faults, the area in between forms a sliver plate. In the case of Burma, the major plates are the Indian plate and the Eurasian plate but the tectonic situation is there is also strongly influenced by the Andaman sea oblique spreading system.

Certainly seen many features that resemble both diapirism and surficial salt flows in Hebes Chasma as well as imagery from other areas that bear a strong resemblance to diapiric uplift. Here's a reference. Let me know if you need the full text.

Jackson, M. P. A., Adams, J. B., Dooley, T. P., Gillespie, A. R., and Montgomery, D. R., 2011, Modeling the collapse of Hebes Chasma, Valles Marineris, Mars: Geological Society of America Bulletin, v. 123, no. 7/8, p. 1596‒1627.

There is also plenty of literature on alluvial fans offset by the Dead Sea Fault or one of its branches:

Klinger et al., 2000: Slip rate on the Dead Sea transform fault in northern Araba valley (Jordan). http://gji.oxfordjournals.org/content/142/3/755.full

Ginat et al., 1998: Translocated Plio-Pleistocene drainage systems along the Arava fault of the Dead Sea Transform. http://earth.huji.ac.il/data/pics/RP28.pdf

Niemi et al., 2001: Late Pleistocene and Holocene slip rate of the Northern Wadi Araba fault, Dead Sea Transform, Jordan. http://link.springer.com/article/10.1023/A:1011487912054

A look at NEW CONCEPTS IN GLOBAL TECTONICS website will reveal

many articles related to the cause and effect of the Moon, Sun, and Earth,

and their alignments, and the strength of the Forces associated

with Tides of different heights. Spring Tides, Neap Tides, etc.

You could spend many months reading all of the articles.

Some Earthquakes occur very soon after a maximum tidal event

occurs, and some of those are associated with famous Tsunamis.

Initials are : NCGT

If you kave karsts in this area, caves are very good natural recorders for active faulting.

Nabajit, let me assume that the river dynamics you are studying is located in the North bank of the upper reach of the Brahmaputra valley. As you are interested in correlating microseismic events with the river dynamics, you must have collected seismic data set say for the last twenty years or so from the NEIST, Jorhat. Assuming you have also collected satellite imageries( twenty/ten sets say, which might be a bit cost prohibitive but perhaps you have managed it) for different years. It is not difficult to isolate most change prone patches by measuring plano-temporal variations in the GIS based environment. Next, you may start drawing concentric circles around those patches and plot the epicenters of earthquakes having different magnitudes. Subsequently, you can go for a statistical correlation. But keep in mind certain other issues. The influence of the Himalayan Frontal Thrusts in the valley (in the form of blind faults, the leading edges etc.) are still not properly mapped (Both the OIL and ONGCL have done some work but published literature are very scarce). Secondly, many smaller faults are associated with some of the major faults. As most of the north bank tributaries of the Brahmaputra carry lots of sediments, the gradual migration of banks is a general sedimentology related issue. Thus, sedimentology plays a dampening effect on tectonic changes. Perhaps frequency filtering technique might help to separate these two things.

Hello James, if Mars is still living depends on our definition of living. In my opinion a planet is living IF there is volcanic activity, IF there is enough internal heat to sustain a geodynamo and subsequent magnetic field that can shield the planet from deadly radiations. Both conditions have gone long time ago, 4.1 Ga for the geodynamo at least and 3.5-3.0 Ga for the volcanism at least. But these dates could be pushed back further. So only the InSight mission can say if there are still traces of internal "life" in a almost dead Mars, I'm personally skeptical about it but we'll see.

Regarding the plate tectonics on Mars, even a blind can see that there are neither traces of subduction zones nor rift zones on the map of Mars. All the features that can be seen on Mars are superimposed on the Martian dichotomy, which is the oldest features of Mars, so nothing disappeared or has been reworked in the meanwhile. If the Valles Marineris is a rift, where is the relative subduction zone??? So I really find incredible how somebody can still talk of Plate Tectonics on Mars today. I explain in a paper that is currently under review the real origin of Valles Marineris, so hopefully in a few time you will see the real nature of it. Stay tuned on my ReserachGate page following me. Cheers, Giovanni.

Rosanna,

I suggest that you compile historical earthquake data and recorded measurements of seiche waves on Lago di Bolsena for those events. Didn't some one note the seiche amplitude for the 1980 earthquake? If not, then perhaps historical photos will show the water line? This may be a question that is easiest to answer with a day or two spent in the library, followed by interviews with residents at the lake.

Too bad I don't have a proper answer, since I can only think of shakemaps for earthquakes occurring near the coastline - i.e. estimates are automatically computed anyway in those cases, although I doubt those estimates can take different attenuation models in account.. It'a fascinating issue..