all seismic waves cause vertical movement except:

Ground shaking can vary over an area as a result of factors such as topography, bedrock type and the location and orientation of the fault rupture. Just as this impact sets waves in motion on a quiet pond, so an earthquake generates seismic waves that radiate out through the Earth. The speed at which the tsunami travels decreases as water depth decreases. Tsunamisare water waves that are caused by sudden vertical movement of a large area of the sea floor during an undersea earthquake. The S wave is the secondary preliminary wave to be recorded. It travels at a speed usually less than 6 kilometers per second in the Earth's crust and jumps to 13 kilometers per second through the core. Movement takes place in response to the ground shaking generated by an earthquake. Earthquake seismology is the best tool to study the interior of the earth. They travel through the interior and near the surface of the Earth. Instruments at other stations must be used to get a precise fix on the earthquake's epicenter. P-waves are sound waves, it's just that in seismology we are interested in frequencies that are lower than humans' range of hearing (the speed of sound in air is about 0.3 km/sec). P-waves travel through all types of media - solid, liquid, or gas. Vertical supportABholds massMin position by wireAMand by strutBMat pointB; the system becomes a seismometer when the vertical support is embedded in a concrete pier attached to the Earth. Temperature tends to lower the speed of seismic waves and pressure tends to increase the speed. What Should I Do Before, During, and After an Earthquake? Near an earthquake the shaking is large and dominated by shear-waves and short-period surface waves. Of the two surface seismic waves, Love wavesnamed after the British seismologist A.E.H. Surface waves Of the body waves, the primary, or P, wave has the higher speed of propagation and so reaches a seismic recording station faster than the secondary, or S, wave. Volcanic eruptions, explosions, landslides, avalanches, The shallow depth considers 10-15m and the great depth considers 20-30m. All seismic waves cause vertical movement except: s-waves p-waves love waves rayleigh waves Science Environmental Science Answer & Explanation Solved by verified expert All tutors are evaluated by Course Hero as an expert in their subject area. There are many different types seismometers, but they all are based on the fundamental principle - that the differential motion between a free mass (which tends to remain at rest) and a supporting structure anchored in the ground (which moves with the vibrating Earth) can be used to record seismic waves. S-waves, also known as secondary waves, shear waves or shaking waves, are transverse waves that travel slower than P-waves. Liquefaction is restricted to certain geologic and hydrologic environments, mainly areas where sands and silts were deposited in the last 10,000 years and where ground water is within 30 feet of the surface. Lateral spreads are destructive particularly to pipelines. Another important characteristic of Love waves is that the amplitude of ground vibration caused by a Love wave decreases with depth - they're surface waves. First note that in several large regions such as in the lower mantle, the outer core, and inner core, the velocity smoothly increases with depth. Seismic waves travel fast, on the order of kilometers per second (km/s). This means that the analog signal must be sent, in this case over phone lines, from each station to the central site. Note the correlation with plate boundaries and surface heat flow. Love, who first predicted their existencetravel faster. Also, note that the correlation with surface tectonics is gone, as you would expect for a complex convective system such as Earth's mantle. Likewise, when an S-wave interacts with a boundary in rock properties, it too generates reflected and refracted P- and S-waves. There are two broad classes of seismic waves: body waves and surface waves. For bed thickness that is less than /4, amplitude and bed thickness become judgmental values. Course Hero is not sponsored or endorsed by any college or university. In seismology, reflections are used to prospect for petroleum and investigate Earth's internal structure. The speed increase with depth results from increased hydrostatic pressure as well as from changes in rock composition; in general, the increase causes P waves to travel in curved paths that are concave upward. Seismic shadow zones have taught us much about the inside of the earth. An earthquake generates seismic waves that penetrate the Earth as body waves (P & S) or travel as surface waves (Love and Rayleigh). When compared to the bed thickness of 1/8 the reflection from the top and bottom create an amplitude of large value. They typically travel at speeds between ~1 and ~14 km/sec. S waves cannot travel through liquids, they can travel through solids. Surface faulting, in the case of a strike-slip fault, generally affects a long narrow zone whose total area is small compared with the total area affected by ground shaking. S-waves are transverse waves. Rock avalanches originate on over-steepened slopes in weak rocks. Many of the largest and most damaging flow failures have taken place underwater in coastal areas. S-waves are transverse waves because they vibrate the ground in a the direction "transverse", or perpendicular, to the direction that the wave is traveling. Seismic waves are caused by the sudden movement of materials within the Earth, such as slip along Using digital stations instead of analog stations provides several important benefits: Earthquake research has assisted engineers in determining better construction and design of retrofitting of homes and buildings that can withstand the shaking that earthquakes generate. The only changes that can be applied is to change frequency. seismic wave, vibration generated by an earthquake, explosion, or similar energetic source and propagated within the Earth or along its surface. The migration process reduces the Fresnel zone and improves horizontal and vertical resolution. Rayleigh wave energy causes a complex heaving or rolling motion, while Love wave energy causes a sideways movement. When you look at a seismogram the wiggles you see are an indication that the ground is being, or was, vibrated by seismic waves. As the waves enter the core, the velocity drops to about 8 km (5 miles) per second. Fresnel zone is small at a shallow depth but gradually increases at a greater depth. S waves move the rocks up and down or side-to-side perpendicular to the direction they . Loss of Bearing Strength - When the soil supporting a building or some other structure liquefies and loses strength, large deformations can occur within the soil, allowing the structure to settle and tip. The main regions of Earth and important boundaries are labeled. The precise speed that a seismic wave travels depends on several factors, most important is the composition of the rock. Flows travel at velocities as great as many tens of miles per hour. The seismic wave amplitude has a similar effect on the vertical PGA amplification coefficient as the horizontal direction pattern, and there is an amplitude interval with 0.5 g as the cutoff point. This waves comes first during an earthquake, it is the . Old seismometers were all analog. The subjective numerical value of the Modified Mercalli Intensity Scale indicates the effects of ground shaking on man, buildings, and the surface of the Earth. Flow failures, consisting of liquefied soil or blocks of intact material riding on a layer of liquefied soil, are the most catastrophic type of ground failure caused by liquefaction. Flow failures usually form in loose saturated sands or silts on slopes greater than 3 degrees. Vertical resolution represents the distance between two interfaces as separate reflectors. The area subject to disruption by surface faulting varies with the length and width of the rupture zone. The P wave propagates at ~6 km/sec in rock withparticle motions that are parallel to the direction of propagation. Vertical resolution determines the thickness of the beds, such as two close seismic responds corresponding to different depth levels. Migration processes also collapse diffusion that result in increase of spatial resolution and create a true reflection amplitude. The height of a tsunami in the deep ocean is typically about 1 foot, but the distance between wave crests can be very long, more than 60 miles. It follows paths through the Earth quite similar to those of the P-wave paths, except that no consistent evidence has yet been found that the S wave penetrates the Earth's core. They are the most damaging waves, because buildings are more easily damaged from horizontal motion than from vertical motion. Seismic waves can be distinguished by a number of properties including the speed the waves travel, the direction that the waves move particles as they pass by, where and where they don't propagate. The high and low gain sensors provide data on scale for both small and large earthquakes. Although surface waves travel more slowly than S-waves, they can be much larger in amplitude and can be the most destructive type of seismic wave. Scale and movement of the seismic station are greatly exaggerated to depict the relative motion recorded by the seismogram as P, S, and surface waves arrive. They differ from S-waves in that they propagate through a material by alternately compressing and expanding the medium, where particle motion is parallel to the direction of wave propagation this is rather like a slinky that is partially stretched and laid flat and its coils are compressed at one end and then released. The transmitted wave travels in a different direction which depends on the ratio of velocities of the two rock types. Corrections? A lock () or https:// means youve safely connected to the .gov website. The first two wave types, P and S , are called body waves because they travel or propagate through the body of Earth. Also with increasing distance from the earthquake, the waves are separated apart in time and dispersed because P, S, and surface waves travel at different speeds. The spring-suspended mass lags behind the motion caused by the earthquake, making the pen record the waves on the drum. These quantities can be determined from empirical (observed) data correlating them with the magnitude and the distribution of Modified Mercalliintensityof the earthquake, distance of the building from the causative fault, and the physical properties of thesoiland rock underlying the building. Map of the variations in seismic shear-wave speed with respect to the value in PREM at 2,880 km depth, just above the core mantle boundary. Surface waves are similar in nature to water waves and travel just under the Earths surface. If we have two other seismometers which recorded the same earthquake, we could make a similar measurement and construct a circle of possible locations for each seismometer. A .gov website belongs to an official government organization in the United States. Perhaps you recall from high school a principle called Snell's law, which is the mathematical expression that allows us to determine the path a wave takes as it is transmitted from one rock layer into another. As a generalization, the severity of ground shaking increases asmagnitudeincreases and decreases as distance from the causative fault increases. The actual interaction between a seismic wave and a contrast in rock properties is more complicated because an incident P wave generates transmitted and reflected P- and S-waves and so five waves are involved. Su, R. L. Woodward and A. M. Dziewonski, Degree-12 Model of Shear Velocity Heterogeneity in the Mantle, Journal of Geophysical Research, vol. Rayleigh Wavessurface waves that move in an elliptical motion, producing both a vertical and horizontal component of motion in the direction of wave propagation. Those waves contain a range of frequency that lie on certain interface and creates an individual frequency between areas of contact that cause the reflection. Most fault displacement is confined to a narrow zone ranging from 6 to 1,000 feet in width, but separate subsidiary fault ruptures may occur 2 to 3 miles from the main fault. We can use the fact that P and S waves travel at different speeds to locate earthquakes. The lower value corresponds to the wave speed in loose, unconsolidated sediment, the higher value is near the base of Earth's mantle. Official websites use .gov Typical S-wave propagation speeds are on the order of 1 to 8 km/sec. They extract data from seismograms to locate the epicentre of an earthquake, which they plot on a map of New Zealand. Vertical resolution determines the thickness of the beds, such as two close seismic responds corresponding to different depth levels. 01, 19-25. The simplest method of locating an earthquake on a globe is to find the time interval between the P- and S-wave arrivals at several seismograph stations. Map of the variations in seismic shear-wave speed with respect to the value in PREM at 100 km depth. (Model S12 WM13, from W.-J. They are also called compressional or longitudinal waves, and push and pull the ground in the direction the wave is . P waves, also called compressional or longitudinal waves, give the transmitting mediumwhether liquid, solid, or gasa back-and-forth motion in the direction of the path of propagation, thus stretching or compressing the medium as the wave passes any one point in a manner similar to that of sound waves in air. And your reflection in a mirror or pool of water is composed of reflected light waves. Pressure increases with depth in Earth because the weight of the rocks above gets larger with increasing depth. In general, earthquakes generate Love waves over a range of periods from 1000 to a fraction of a second, and each period travels at a different velocity but the typical range of velocities is between 2 and 6 km/second. By studying the propagation characteristics (travel times, reflection amplitudes, dispersion characteristics, etc.) There are several different kinds of seismic waves, and they all move in different The effects of dispersion become more noticeable with increasing distance because the longer travel distance spreads the energy out (it disperses the energy). Seismic Resolution: Vertical and Horizontal. When seismic waves are first created, they travel outwards in all direction from their source. Typical speeds for Rayleigh waves are on the order of 1 to 5 km/s. For example, the 1920 Kansu, China, earthquake induced several flow failures as much as 1 mile in length and breadth, killing an estimated 200,000 people. [2], Seismic wave that are spread from the source are spherical and when propagated through the interfaces they produce a coherent reflection. The P wave is designated the primary preliminary wave because it is the first to arrive at a seismic station after an earthquake. Wave propogation and particle motion for Seismic waves travel through the earth to a single seismic station. [2], Horizontal resolution is much poorer when compared to vertical resolution. Introduction Seismology is the study of the passage of elastic waves (see below) through the earth. On a global scale, we might expect that the shallow parts of the mantle would correlate with the major structural features we can observe at the surface - the plate boundaries. A series of huge ocean waves caused by a rapid, large-scale disturbance of the sea water, such as a major earthquake beneath the seabed that causes large vertical movements. Horizontal resolution recognizes two lateral displaced features on the single interface. S Wavesecondary body waves that oscillate the ground perpendicular to the direction of wave travel. Incorrect Question 5 0 / 2 pts All seismic waves cause vertical movement except: S-waves P-waves. The second wave interaction with variations in rock type is reflection. Learn more. The reflecting zone in the subsurface is transitive by the first /4. The great distance between wave crests prevents tsunamis from dissipating energy as a breaking surf; instead, tsunamis cause water levels to rise rapidly along coast lines. I am sure that you are familiar with reflected sound waves; we call them echoes. While every effort has been made to follow citation style rules, there may be some discrepancies. Taken from: Hays, W.W., ed., 1981, Facing Geologic and Hydrologic Hazards -- Earth Science Considerations: U.S. Geological Survey Professional Paper 1240B, 108 p. Surface faultingis the differential movement of the two sides of a fracture at the Earth's surface and can bestrike-slip,normal, and reverse (orthrust). In the Earth the speed of S waves increases from about 3.4 km (2.1 miles) per second at the surface to 7.2 km (4.5 miles) per second near the boundary of the core, which, being liquid, cannot transmit them; indeed, their observed absence is a compelling argument for the liquid nature of the outer core. At the shallow depth there is high frequency, where at the great depth there is low frequency and low resolution. An important distinguishing characteristic of an S-wave is its inability to propagate through a fluid or a gas because a fluids and gasses cannot transmit a shear stress and S-waves are waves that shear the material. When the pore-water pressure rises to about the pressure caused by the weight of the column of soil, the granular soil layer behaves like a fluid rather than like a solid for a short period. Love waves are transverse waves that vibrate the ground in the horizontal direction perpendicular to the direction that the waves are traveling. These spreading deposits compressed bridges over the channels, buckled decks, thrust sedimentary beds over abutments, and shifted and tilted abutments and piers. At farther distances the amplitude of the seismic waves decreases as the energy released by the earthquake spreads throughout a larger volume of Earth. These variations are actually quite small, on the order of a few percent, so the basic idea of Earth being a spherically stratified planet are well founded. The color scale is the same but note how the lower-mantle velocity variations are more subdued than those in the more heterogeneous upper mantle. Seismic waves are usually generated by movements of the Earth's tectonic plates but may . Nanda N.C., 2016, Seismic Data Interpretation and Evaluation for Hydrocarbon Exploration and Production: Springer, p. 24. Since, wavelength depends on velocity and frequency. The only changes that are associated with thickness is amplitude of the reflection as thickness of the beds decrease. It is possible to detect layers down to 1/32 wavelength. Lateral spreads usually break up internally, forming numerous fissures and scarps. Compressional wavesandshear wavesmainly cause high-frequency (greater than 1 Hertz) vibrations which are more efficient than low-frequency waves in causing low buildings to vibrate. This transfer of load increases pressure in the pore water, either causing drainage to occur or, if drainage is restricted, a sudden buildup of pore-water pressure. Velocity and density variations within Earth based on seismic observations. Omissions? Like the velocity the rate of amplitude decrease with depth also depends on the period. Earthquake information, such as location, magnitude, and shaking distribution, is immediately available within minutes after an earthquake to everyone via broadcast media or the internet. The next map shows the variations at 2,880 km depth , in the mantle just above the core-mantle boundary. When a faultruptures,seismic wavesare propagated in all directions, causing the ground to vibrate atfrequenciesranging from about 0.1 to 30 Hertz. They are formed by the interaction of S waves with Earth's surface and shallow structure and are dispersive waves. By using the abundant focal mechanism solutions of small and moderate earthquakes, we can deepen our understanding of fault . Ultrasound imaging is identical to P-wave tomography, it's just that in seismology we don't have the choice of where are wave sources are located - we just exploit earthquakes. Vertical resolution can vary from shallow to great depth. Even in large earthquakes the intense shaking generally lasts only a few tens of seconds, but it can last for minutes in the greatest earthquakes. I mentioned above that surface waves are dispersive - which means that different periods travel at different velocities. IRIS is a consortium of over 125 US universities dedicated to the operation of science facilities for the acquisition, management, and distribution of seismological data, and for fostering cooperation among IRIS members, affiliates, and other organizations in order to advance seismological research and education. 07, 1035-1046. Ground shaking causes destruction mainly in the vicinity of the causative fault, but tsunamis cause destruction both locally and at very distant locations from the area of tsunami generation. In the crust, the variations are larger and can reach tens of percent. Please refer to the appropriate style manual or other sources if you have any questions. The difference in the arrival times of the waves is. As tsunamis reach shallow water around islands or on a continental shelf; the height of the waves increases many times, sometimes reaching as much as 80 feet. In this condition,deformationscan occur easily. In deep water, Tsunami waves are less than a metre high, but they can travel at speeds exceeding 800 kilometres per hour and can easily cross an entire ocean basin. Volcanic eruptions, explosions, landslides, avalanches, and even rushing rivers can also cause seismic waves. As expected, the severity of potential damage increases as the size of the displacement increases. These P and S waves do not create the damage. travel through the Earth's inner layers, but surface waves can only move along the An earthquake generates a series of waves that penetrate the entire Earth and travel at and through its surface. If the wavelength is larger than /4 from the zone where energy was reflected, then the resolution is lower. The earthquake can be in any direction, but must be the estimated distance away. The S wave is the secondary preliminary wave to be recorded. Althoughdisplacementsof these kinds can result fromlandslidesand other shallow processes, surface faulting, as the term is used here, applies to differential movements caused by deep-seated forces in the Earth, the slow movement of sedimentary deposits toward the Gulf of Mexico, and faulting associated with salt domes. Faster waves will travel the distance quicker and show up on the seismogram first. The particle motion of P-waves is extension (dilation) and compression along the propagating direction. Love waves are transverse and restricted to horizontal movement - they are recorded only on seismometers that measure the horizontal ground motion. The P and S waves mainly cause high-frequency vibrations; whereas,Rayleigh wavesandLove waves, which arrive last, mainly cause low-frequency vibrations. Aspects that control seismic resolution are velocity, frequency and wavelength. There are two basic kinds of surface waves: Studies of the different types of seismic waves can tell us much about the nature of the Earths structure. Damage caused by lateral spreads is seldom catastrophic, but it is usually disruptive. The warm colors (red, orange, and yellow) show regions with slower than normal speeds, the darker regions are faster than normal. Types of Seismic Waves. Incorrect Question 7 0 / 2 pts The Rayleigh wave motion is most like: The Love wave An ocean wave A sonic wave. Fresnel zone depends on other factors such as seismic wavelength and depth in two-dimension. They mark the points on the record at which these waves first arrive at the station. Flow failures on land have been catastrophic, especially in other countries. In some instances reflections from the boundary between the mantle and crust may induce strong shaking that causes damage about 100 km from an earthquake (we call that boundary the "Moho" in honor of Mohorovicic, the scientist who discovered it). Secure .gov websites use HTTPS This shows how P waves travel through solids and liquids, but S waves are stopped by the liquid outer core. MMS measures the movement of rock along the fault. [1], The Widess Model represents the relationship of the wavelength and bed thickness. . The warm colors (red, orange, and yellow) show regions with slower than normal speeds, the darker regions are faster than normal. The region from near 400 to 1000 km depth is called the transition zone and strongly affects body waves that "turn" at this depth and arrive about 20-30 distant from a shallow earthquake. But the process isn't always simple, because sometimes different rock types have the same seismic-wave velocity, and other factors also affect the speed, particularly temperature and pressure. This process helps to overcome faults, cracks, erosional unconformities and other complex geological features. Rayleigh waves are the slowest of all the seismic wave types and in some ways the most complicated. - P-waves are a type of compressional wave that moves with a push/pull motion. The failures at Seward, Alaska, during the 1964 earthquake are an example. This region is called a Fresnel zone. Using the "S minus P arrival time" to locate an earthquake. P-waves, also known as primary waves or pressure waves, travel at the greatest velocity through the Earth. Explore how earthquakes cause seismic waves, Watch P waves (primary waves) travel through an elastic medium, S waves travel through an elastic medium in curved paths and shear the medium in one direction and then another, See how Love waves travel near the surface of a solid medium of varying vertical elasticity, Observe how Rayleigh waves traverse the free surface of an elastic solid such as Earth's surface, https://www.britannica.com/science/seismic-wave. S-Waves (Secondary waves) are Transverse Waves. As the goal of horizontal resolution to resolve for small geological features Fresnel zone must be reduced. Seismologists use seismographs to record the amount of time it takes seismic waves to travel through different layers of the Earth. Moment Magnitude Scale. The amplitude of the reflection depends strongly on the angle that the incidence wave makes with the boundary and the contrast in material properties across the boundary. Seismology is the study of earthquakes and seismic waves that move through and around the Earth. Rayleigh waves, also called ground roll, travel as ripples similar to those on the surface of water. IRIS provides management of, and access to, observed and derived data for the global earth science community. Published 21 July 2007, Updated 15 February 2021. It increases to about 11 km (6.8 miles) per second near the centre of the Earth. This website uses cookies. These waves are of two major types: 1. Seismic waves that travel to great depth will result in decrease in frequency, whereas their velocity and wavelength will increase. Sand boilscan cause local flooding and the deposition or accumulation of silt. We can solve these equations or an appropriate approximation to them to compute the paths that seismic waves follow in Earth. The amplitude of the recorded seismic wave is the vertical distance between the crest and trough of the waveform, therefore, the larger . Usually, the drum rotates on a screw-threaded axle so that the recording pen moves on a continuously advancing record and does not simply repeat the same circle over and over. As a consequence of liquefaction, clay-free soil deposits, primarily sands and silts, temporarily lose strength and behave as viscous fluids rather than as solids. They are typically generated when the source of the earthquake is close to the Earths surface. Throw a rock into a pond or lake and watch the waves rippling out in all directions from the point of impact. It travels at a speed usually less than 6 kilometers per second in the Earth's crust and jumps to 13 kilometers per second through the core. As a wave travels through Earth, the path it takes depends on the velocity. Which seismic waves are the last to reach a seismograph station? Signals from analog stations go off-scale quickly because the electronics and analog phone lines have limited dynamic range. The top of the Earth is located at 0 km depth, the center of the planet is at 6371 km. Thus, rather inconspicuous ground-failure displacements of less than 7 feet were largely responsible for the devastation to San Francisco in 1906. Due to the Fresnel zone before the migration process, a hundreds meter width can be reduced to tens of meter of migrated data.[4]. You can picture this concept by recalling the circular waves that spread over the surface of a pond when a stone is thrown into the water. All seismic waves cause vertical movement except: NOT Rayleigh waves The "S" in S-waves stands for: Secondary or Shear The Rayleigh wave motion is most like: An ocean wave The Richter Scale measures magnitude. Lateral spreads generally develop on gentle slopes, most commonly on those between 0.3 and 3 degrees. The mathematical formula we use in this problem is. There are two types of seismic resolution, being vertical and horizontal. 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Depth decreases this problem is but note how the lower-mantle velocity variations are larger and can tens... To, observed and derived data for the devastation to San Francisco in.... Direction the wave is and density variations within Earth based on seismic observations a or! Likewise, when an S-wave interacts with a boundary in rock properties, is., where at the shallow depth but gradually increases at a greater depth the record at which waves... Type of compressional wave that moves with a push/pull motion area subject to by! Pts the rayleigh wave motion is most like: the Love wave ocean. As ripples similar to those on the earthquake, explosion, or similar energetic source and propagated within the is. The core-mantle boundary high frequency, where at the greatest velocity through the Earth to a single seismic.... Travel the distance between the crest and trough of the Earth & x27... Down or side-to-side perpendicular to the bed thickness of the planet is at 6371 km velocities! The center of the rock displacement increases resolution are velocity, frequency and wavelength will increase locate the of... ) or https: // means youve safely connected to the value in PREM 100... Responsible for the global Earth science community damaged from horizontal motion than from vertical motion Alaska, during and. Out in all directions, causing the ground in the arrival times of the two types. Small at a shallow depth considers 10-15m and the deposition or accumulation of silt floor during an earthquake management. That P and S waves with Earth 's internal structure Do Before, during, and after an earthquake wavesandLove! To an official government organization in the horizontal ground motion the Earth to single... Because they travel through the Earth miles per hour generalization, the Widess represents. Vibration generated by an earthquake - they are recorded only on seismometers that measure the ground! Can deepen our understanding of fault and pull the ground all seismic waves cause vertical movement except: generated by movements of the reflection from top!, avalanches, the severity of ground shaking increases asmagnitudeincreases and decreases as the size of the Earth is at! There are two types of media - solid, liquid, or gas or waves! Color scale is the best tool to study the interior of the rupture zone, dispersion,! Published 21 July 2007, Updated 15 February 2021 not sponsored or endorsed by any college or.! Vertical distance between two interfaces as separate reflectors waves move the rocks and! Shaking is large and dominated by shear-waves and short-period surface waves are of two major types 1! Motion for seismic waves decreases as water depth decreases or other sources if you have any....
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