Deep faults of the Moon and multiple reflected waves Satoshi Tanaka* (ISAS, JAPAN), Khavroshkin O. B**., Tsyplakov V. V.** *ISAS, JAPAN **Schmidt Institute. - презентация
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Презентация на тему: " Deep faults of the Moon and multiple reflected waves Satoshi Tanaka* (ISAS, JAPAN), Khavroshkin O. B**., Tsyplakov V. V.** *ISAS, JAPAN **Schmidt Institute." — Транскрипт:
Deep faults of the Moon and multiple reflected waves Satoshi Tanaka* (ISAS, JAPAN), Khavroshkin O. B**., Tsyplakov V. V.** *ISAS, JAPAN **Schmidt Institute of Physics of the Earth, Russia, Phone
At 1-st stage of development of researches of an internal structure of the Moon the model with deep "open" faults (fig.1,2) was considered. That is with main faults contact surfaces between which boards seismically were not effective and roots of faults left in the top mantle [1-3].
Fig.1. Heterogeneity and blocks of an internal structure of the Moon.
Explanation for Fig.1 И1, И2 - the seismic beams proceeding from a source И; И1к, И`1к - the seismic beams reflected from real border of a corn and from assumed integrated border accordingly; И2к, И2к - the same, as for case И1; Δθ01, Δθ02 - mistakes in an estimation of a direction of the reflected seismic beam at use of integrated model; - Δθ01 ~ θ0, the same and within the framework of the standard model of the Moon.
Consideration of applicability of a beam method for real model of the Moon bring results in probable (almost inevitable) mistake Δθ in tens degrees (Fig. 2) that excludes application of classical seismology and explains long-time failures in searches of borders of a corn. Thus the basic problem is not the organization (radiation) of powerful probing impact but an identification on seismogram introductions of the seismic waves reflected from borders of a corn. So search of seismological methods of relatives to classical is necessary but allowing to come nearer to representations about an internal structure of the Moon. We shall consider in more detail display blocks in various sites of seismogram and influence block structure on distribution of waves from powerful impacts (falling of meteorites) that is accompanied by seismic activation of region. Display of existence of the several nonlinear seismic effects which have been found out on the Earth is obviously allowable. Thus, the initial stage of development of nonlinear seismology was sufficient for attempt to transfer terrestrial experience on studying of lunar seismicity and the analysis lunar seismogram. Features of geological structures of the Moon and the form of records seismograms became the precondition and the certificate of existence strong modulation effect. As well as in the general physics modulation in lunar seismology (as well as in terrestrial) - change under the known law (the law of external influence) in time of parameters of a seismic wave field. Therefore understanding of the Moon as megadetector external field and impact influences and the account of nonlinearly of processes have resulted in reception of significant results on cosmology and to an internal structure of the Moon [5-10]. The above- stated results and the common understanding have allowed to accept not only nonlinear model of seismicity of the Moon but also existence of seismic acoustic processes and first time seismic acoustic emission.
Existence of seismic acoustic processes for revealing a place of faults and which role were analyzed two most strong seismogram for all time of supervision from impacts of meteorites. 1-st impact was May, y. in 142 km. to the north from « Apollo 14 », diameter of a meteorite 2m.; speed of impact 20¬km/s, diameter of a crater 100m, devices on « Apollo 12,14 » were out limit record, records on « Apollo 15,16 » on distance 967 and 1026km accordingly were good. 2-nd impact was July, y., fare side of the Moon on area of a crater "Moscow", a trotyl equivalent 1000t.Externally both seismograms have a little common with terrestrial traditional: their duration on orders surpass durations of records even powerful earthquakes. Lunar record consists of practically clean sites with almost imperceptible display of a signal and various escape of a level concerning significant both on amplitude and on duration. Parameters of escape are poorly connected to the moments of their time arrival. The similar form of seismogram record is not observed on the Earth. However, under the form and display of escape record strongly reminds the data on registration of seismic acoustic process beside active Ashkhabat fault after Gazlijskogo earthquake y. which was accompanied by a long regional motion. On the Moon similarly both meteoric impacts, 1-st is especial, have made on region of falling and on all Moon dominant the basic triggers influences which have resulted in dump of potential elastic energy of geological matter. Believing a nature of features of the above-stated records on the Earth and the Moon close on the physical mechanisms we compare their forms (fig.3), thus using earlier accepted terminology and classification.
Fig.3 (a-g). Types of peak escape lunar seismogram envelope and records and seismogram in seismic active regions of the Earth: similarities and distinctions (z-component).
Fig.3 (a). An example of record of peak escape lunar seismogram envelope for impact of a meteorite (Z a component) at station «Apollo 15, 16 » 13 May 1972y. Type escape is named abrupt forward front (AFF)
Fig.3 (b). Other an example of record of peak escape lunar seismogram envelope for impact of a meteorite (Z a component) at station «Apollo 15, 16 » 13 May 1972y. Type escape is named abrupt forward front (AFF)
Fig.3(c). Example of record of peak escape seismogram envelope for of seismic acoustic noise on the specially equipped point of registration beside Ashkhabat fault. Type escape is abrupt forward front (AFF)
Fig.3 (d). An example of record of peak escape lunar seismogram envelope for impact of a meteorite (Z a component) at station «Apollo 15, 17 »;15; 17, July 1972y. Type of escape is Bell form (BF)
Fig.3 (e). The same process as on Fig.3 (d), record at station " Apollo " 15.. Type of escape is Bell form (BF)
Fig.1 (f). Example of record of a site as an escape of amplitude seismogram envelope on the Moon July, y. Type of escape is discrete - line site (DLS)
Fig.1 (g). Example of record of peak escape seismogram envelope for of seismic acoustic noise on Z component on the specially equipped point of registration beside Ashkhabat fault. Type of indignation is discrete - line site (DLS)
Types of forms of escape or signals with forward abrupt front have the greatest similarity (Fig.3a-b). The similar type of a signal for the Moon is most distributed, its nature probably is caused by fragile destruction and/or failure of gearing of micro cracks boards or geological faults. It is especial for a case of autogeneration in the geological structures with internal dry friction. Similarity is traced in the next: a steep ness of front and the subsequent smooth falling of amplitude of a signal; occurrence of very weak rise of noise level before front with emissions and occurrence of the tendency to modulation of noise level of a falling part of a signal. Lunar signals a bell forms are frequent and their differences from terrestrial are insignificant (Fig.3 d,e). AFF signals envelope contains discrete - line emissions.
. Envelope of escape caused by the tendency to autogeneration and also time sequences of signals are observed . The bell form most likely is connected to transformation of an initial signal at its passage through nonlinear dissipation geologic medium and can have solitary peculiarities. Also meeting discretely – line signals on records of lunar and terrestrial events have features: an amplitude line emissions indignation on lunar seismograms surpass the smoothed basis of a signal in 2-3 times while terrestrial up to 10 times. In case of advanced block and fractal geological, energy saturated medium and activation of local seismicity frequently observe display of seismic autogeneration down to occurrence quasi harmonic signal . It is typically for many lunar seismograms [14, 15]. While one form of a signal is not typical for lunar seismicity it is with abrupt back front only and characteristic times of signals coordinate about earlier received data (Fig.4a-l).
Fig. 4 (a-l) Comparison of signals forms or emissions escape of envelope for various processes of wave radiation of (from) elastic potential energy: (a-c) - forms of set of earthquakes [Mogy, 1963]; (d-f) simulation of a seismic mode; (g-i) - types of seismic emission indignation; (j-l) - acoustic emission. It specifies cosmogony unity of physical mechanisms of behavior for the geophysical environment. Above the given data on records of seismic emission beside Ashkhabad (Turkmenia) on amplitude lay in a range m/Hz and amplitude of lunar signals is in a range ·10-11m/Hz that testifies to a uniform physical picture of the specified wave fields.
Studying of forms and structures seismograms allows to draw the following conclusions. 1. Lunar seismogram as records of a seismic signal or event usually consist of one or several parts of which duration and quantity is connected to energy of initial event. 2. The characteristic forms of lunar seismogram similar to forms of seismic acoustic emission on records of seismic acoustic noise on the Earth especially for seismic active zones and during activation of the nearest faults. 3. Lunar sites of records seismogram as well as envelope of seismic acoustic emission signals on the Earth records satisfy to the typified forms of signals inherent in processes of micro – and- macro destruction and plastic deformation of a firm body and rocks, and are characterized by a similar range of frequencies and energy. 4. The analysis lunar seismogram by usual methods of the classic seismology has basic restrictions but their updating with attraction of methods and effects of nonlinear seismology is possible.
Therefore for lunar records of signals with the big amplitude and unicomponent type the seismogram will be three components. This is a clue for search and select of lunar seismograms which is a result of a multiple reflected waves exist. Deep faults of the Moon will help to existing of that waves. For example. Mizutani H. case (fig.5). The kepstrum (spectrum from ln spectrum) analyze is applied for distinguish of a multiple reflected waves too.
Fig.5.Channeling seismic energy of moonquake on Mizutani H.
For Fig. 5 1-lunar lithosphere, 2-nucleus, 3- moonquake center, 4-wave field from the center extending to a corn, 5-waves in a corn, 6-waves past a corn, 7-waves 6 in a crust, 8-wave field which radiated to a day time surface.
Fig. 6. An example of a mutual spectrum from realizations of a code envelope of X component of a meteorite of 133 seismic on stations А12, А14.
Fig. 7. Kepstrum (a spectrum from a ln spectrum) from a spectrum of realizations Fig. 6.
Fig. 8. A mutual spectrum from realizations of an envelope code Z component of a meteorite of 199 on seismic stations А12, А14.
Fig. 9. Kepstrum from a spectrum of realizations Fig. 8.
Let's compare spectra fig.8. Despite of a lot of significant spectral peaks of realization codes X components (fig.6) kepstrum of this spectrum (fig.7) has not strongly pronounced significant peaks and represents smooth enough falling down curve that testifies to absence in researched process of multiple waves, or proves absence of lamination (reflecting borders) in a direction X component. Thus spectral peaks (fig.7) are caused or FOM, or own oscillations of registration region. On the other hand, the spectrum of realizations Z making (fig. 8) has powerful strongly pronounced spectral peaks, as well as its kepstrum (fig. 9). The last proves existence of horizontal lateral lamination or reflecting borders in region of registration which are the reason appear of a multiple reflected waves too.
The seismic data of two impact of meteorites was used (look above). Statistic analyze (spectrums, kepstrums) of all seismograms was presented on 10 tables but the results of discovered of a multiple reflected waves presents by table 1 where is the comparison between the recorded characteristics times (periods) of that waves and known periods which received from known geologic models of the Moon.
Example Upper mantle ; 7.7±0.2; 4.3±0.15; 1.28min; 2.8min; 1.3min; 2.3min; 350km; 7.8=V p ; 4.3=V s 38.5c.;70c.; Toksoz
Data table time-structure In Table 10: 1-st column - elements of structure; 2 - capacity of each element (ΔR, km); 3 - speed of a longitudinal wave Vp, km/c; 4-speed of a cross wave Vs, km/c; 5-period multiple Р waves for system a day time surface - the top border of a structural element (Тр min.); 6 - too for S waves (Тs min.); 7,8 - the periods multiple P, S waves in element of structures (Тр min, Тs min); 9-11 too as 1-3 (Δkm,,) but average; 12,13 time of passage P, S waves through the appropriate elements of structure (tp с, ts с).
Conclusion 1. Lunar seismic sources originally can radiate waves of two types - well-known type and a seismic acoustic nature, the last, as a rule, then dominate and complicate interpretation of a wave field. 2. Under the characteristics seismic acoustic signals are similar to the same signals on the Earth, according to their property are well predicted. 3. Deformation lunar lithosphere by seismic waves and processes of a wide frequency range is accompanied by radiation and modulation of high-frequency seismic acoustic waves of emission type. 4. Deep breaks of the Moon promote formation from powerful impact sources of multiple waves such as type PKiKP, and also РсР etc. 5. Time characteristics processes of modulation (FOM) and multiple waves are an authentic material for research of an internal structure of the Moon. 6. The place of landing of lunar stations is necessary for choosing in view of registration of multiple waves.
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