Ludger Mintrop (July 18,1880 - January 1, 1956) was a German mine surveyor and geophysicist. Mintrop is considered the inventor of the seismic method for exploration of hydrocarbons and minerals (Patent 1916), through the seismic refraction method. Among the many accolades and awards in recognition of his seminal work in seismic prospecting, Mintrop was awarded SEG Honorary Membership.
The Decisive Years
Ludger Mintrop was born the fifth son of 15 children on July 18, 1880 at his parents’ Barkhoven estate near Essen-Werden. He passed his matriculation examination at Aachen Grammar School. Subsequent to a thorough practical training in the Ruhr mining industry, he studied at the Mining Academy in Berlin and at the Technical University in Aachen under Professor Karl Haussmann. In 1905, after passing the civil service examination, he obtained his papers to become a mining surveyor and then returned first of aIl as an assistant to Haussmann, where he experienced the decisive contact with geophysics. After setting up a seismic station in Aachen based on the Goettingen prototype, he moved in 1907 to study with Wiechert in Goettingen and was encouraged to undertake thorough tests with artificially produced earthquakes and to construct more easily transportable seismographs. Upon his appointment as a lecturer in mining surveying at the School of Mines in Bochum, he set up here too a seismic station, but at the same time pursued his ideas of applying seismics to practical purposes. Another important event occurred in this period. He married Elisabeth Sartorius in 19 10. The marriage bore five children; two sons were later to fall on the battlefields of the Second World War.
Mintrop had become a commuter: he taught in Bochum and studied in Goettingen. In 1911 he obtained his doctorate under Wiechert with a study: On the propagation of ground oscillations produced by the pressure of the mass of a large gas machine. The seismogram of an artificial earthquake produced by dropping a four-ton steel ball---a donation by the Krupp Company---from a height of 14 m is also to be found in his dissertation.
The First World War saw Mintrop in the prime of life. First he served as a physicist with the Airship Division and later with the Artillery Control Commission. He long tried in vain to convince the general staff that he was in a position with his portable seismographs to determine quickly and accurately the position of enemy gunfire. Only after the bloody Somme massacre was Mintrop able to convince Ludendorff’s general staff of the possibilities of seismic locating. As a consequence, a demonstration of his method was made toward the end of 1916 at the Wahn artillery firing range. Mintrop located the “enemy battery” with such precision that Ludendorff approved 100 locating crews and wanted them at the front in 1917.
The general staff gave the order and Mintrop threw himself into his work. However. qualified personnel and even suitable materials were scarce. and by the end of the war, the desired mass production of seismographs had never been attained.as his colleagues on the other side who attempted to locate the firing batteries by measuring the sound waves through air. Among those were John Karcher and William Haseman. scientists with whom he later had to cross swords as competitors. Sweet wrote about this branch of the services not altogether without irony:
- Sound ranging had a two-part function. The first problem was to
- locate the Position of the enemy guns and the second problem was
- to convince your artillery that they should train their fire on the
- position you had spotted.
As early as 1917, that is still during the war, Mintrop applied for patents for a light field seismograph as well as for a technique to determine the location of artificially produced vibrations. By December 7, 1919, he was able to apply for his famous patent concerning a seismic “method of investigating the structure of strata.” The foundations had been laid.
Patent and technique.
What could Mintrop offer the geologists? Two things: Firstly a light field instrument with great precision- relatively, of course-and secondly a technique that is known today as refraction seismics. Mintrop understood the nature and travel- paths of those bead waves or “indirect waves”---as he called them---which geophysicists of our day refer to as the Mintrop wave. Using the time-distance diagrams, the traveltime curves. he calculated the depth and course of the refracting layer.
A classic depiction shows Mintrop’s system in the working position: on the right is the vertical pendulum---the geophone-- and on the left the photographic unit--the recording instrument. The mass of the pendulum was made up of a 4 kg lead ball suspended elastically from a laminated spring. As a result of its inertia as a static pole, the mass remained stationary when seismic waves affected the housing and made that vibrate. The relative movement between the static mass and the moving surroundings had then to be amplified and recorded Mintrop solved this problem with an ingenious system made up of laminated springs, mirrors, a directing magnet that returned the mirror to its resting position after tilting, a convex lens and the light recorder, which, set up 1 meter from a field seismograph sent a concentrated light beam to the mirror of the seismograph and picked it up again to record it photographically. The theoretical amplification of this mechanical-optical system depended solely upon its dimensions. It was directly proportional to the length of the arm (SO cm) and the distance between the two instruments (1 m), and should have been 50 000. In fact. it was considerably smaller. This was due to the inertia of the arm, the amount of attenuation, the natural period of the pendulum (0.3 s) and last but not least the frequency of the incoming oscillations.
A critical point of the method was the determination of the shot release which had to he known exactly for the interpretation of the curve data. Mintrop had made it known that he had commissioned the Company Siemens & Halske to develop transmitter and receiver equipment for the wireless transfer of the shot release. His patent in 1919 included this at any rate. It was finally available in 1926! Up to that time Mintrop used a makeshift solution: He recorded the arrival of the sound wave in air and calculated from It the moment of the shot release, for the source-receiver distances were known. In order to determine the exact velocity of sound the air temperature, wind direction and wind velocity had to be considered By using so-called blastphones, Mintrop was able to improve the arrival of the sound wave and reserved a separate trace for it on the seismogram. Nevertheless, even after the introduction of radio transfer of the shot release, the sound wave recording was generally still made. In areas with difficult access, it was thus possible to do away with an exact fixing of the transmitter station: The distance between the transmitter and receiver was calculated simply from the travel time of the air wave.
When Mintrop founded SEISMOS on April 4. 1921. financed by the Thyssen, Rheinstahl, Phoenix, Hoesch and Deutsch-Lux mining companies, he had already field-tested his technique. While surveying at Neuengamme near Wietze he had &stinctlY picked up the then unknown Meissendorf salt dome and in doing so had acquired the first significant experience. It was mining and not oil companies that were primarily interested in the new technique This indicates that industry believed to have within its grasp an instrument for detecting the boundaries of ore and coal deposits The capital of the new company “for exploring subsurface layers and mineral deposits” amounted to one million Reichmarks. That wasn’t much. But where did the experts come from? They had to be trained. At the end of the first business year, SEISMOS was made up of eight men.
In March 27. 1923, the first SEISMOS crew took to sea. The destination was Tampico in Mexico. or more precisely, the jungle between ‘Tampico and Veracruz. The famous Golden Lane oil fields WIT to be further investigated in then unexplored zones. Otto Guessenhainer, likewise a pupil of Wiechert, headed the Undertaking At that time the client was the Mexican Eagle Oil Company (El Aquila), creation of the legendary Lord Cowdray and from 1918 a subsidiary of Shell.
Nowadays a seismic crew fills half a ship. All that was needed then were a couple of cabins. Geussenhainer wrote in a letter to George Sweet:
- The whole technical equipment consisted of one Mintrop seismograph,
- one photographic recorder and one observation tent. The whole seismic
- outfit weighed less than the personal luggage of the three SEISMOS men.
It should, however, be mentioned that Mintrop quickly complemented his Mexico Crew 1 with two further seismographs. One of these systems can be seen today in the German Museum in Munich.
The company’s second crew on the American continent started work in the same year under Mintrop’s personal guidance in Oklahoma for Marland Oil. Soon interest was turned toward the region that was predestined to be surveyed by refraction seismics---the Gulf coast of Texas and Louisiana. In April 1924, Geussenhainer’s Party 1 left Mexico for Texas. The explosives were needed in Mexico for one of those numerous revolutions. The Gulf Production Company had charted the crew. First of all, Geussenhainer had to prove his handiwork on several known salt domes; subsequently, he and his men were sent to Ford Bend County in Texas. This is what Geussenhainer had to say about the proceedings (from a letter to Sweet):
- . . .The Gulf people believed there was a salt dome associated with
- a conspicuous bend in the Braxos River and two unsuccessful tests
- had been drilled on this theory. But all of these facts were kept
- secret; we were merely told to shoot such and such lines and see
- what we recorded. Since the first shots showed nothing and were
- completely normal, I took the responsibility of moving our seismic
- equipment about five miles to the southwest. The first shooting in
- this new area indicated the presence of high-velocity material. More
- detailed work in this region convinced me that a salt uplift must be
- there. The typical and characteristic symptoms of a salt dome could
- be seen on the seismograms. Before reporting to the Gulf Company
- concerning the find, I wired Dr. Mintrop in New York City.
- He caught the next train to Houston. This was late in June 1924.
- After Mintrop’s arrival, additional seismic profiles were shot in all
- directions. All the shooting told the same story; all of it confirmed
- my original analysis and properly established the location and ex-
- tent of the salt dome. On September 20,1924, Mintrop and I fixed
- a point “K” on the map of the area under investigation and
- proposed to Gulf that they drill a test well exactly at that spot. The
- geologists of the Gulf Production Company were somewhat skeptical
- about the location “K” because it did not coincide with their
- preconceived ideas of “creekology.” Nevertheless, they decided
- that the only way to test the Mintrop method was to drill where we
- said to drill and with some misgivings they gave order to that effect.
- My English was not so good at the timebut I could tell that here
- were a number of doubters in the Gulf organization. There was a
- lot of laughing and joking about the “German well location.” Mr.
- Paul Weaver’s command of the German language was good and he
- was fond of joking with me in my native tongue. Once he said:
- “Doctor, if this well really and truly hits the caprock, you know
- what we are going to call the well? Peachtree No. 1 of Orchard.”
- The official designation of the test well was Moore No. 1. On
- November 19.1924, the Moore well hit caprock at a depth of 350
- feet, almost the exact depth we had predicted. In December the
- Moore well came in as an oil producer. Originally the oil field that
- developed there was referred to as the Moore field but in time the
- salt dome and the oil field at the salt dome were called Orchard
- after the nearby village of Orchard. No one joked anymore about
- “Peachtree No. 1.” The news spread like a prairie fire and caused
- the utmost excitement in petroleum circles.
Elsewhere Geussenhainer wrote that skepticism of the new technique was considerable in the beginning and that the Mintrop instrumentation was seen as little more than a new type of divining rod. After the discovery of the Orchard, this attitude changed all at once and Sweet described the facts pithily in his History of Geo- physical Prospecting:
- Mintrop's initial success, at the Orchard dome in Fort Bend County,
- Texas, was the biggest event in geophysical exploration history,
- for it put the contracting seismograph company in business to stay.
- Thus, the Mintrop seismograph was responsible for finding both
- the first salt dome, Meissendorf, and the first oil-rich salt dome,
Two years after its discovery, the Orchard field produced 400 tons of oil daily from a 1150 m deep well on the east flank of the salt dome. Compared to the flow from a “giant,” the Orchard was rather a modest success. But nevertheless the effect caused by this find was scarcely less important than the consequences of the Drake pioneer well.
The second spark had therefore detonated in Texas. And the Gulf region felt the effects. Geophysics took a Brm hold. After the Spindletop wildcat strike in 1901, Texas lost considerable ground in oil production. For years efforts had been made in vain.
Now, however, the key to the treasure chest was there for the asking. And the name of the key was applied seismics. Geussenhainer found another three salt domes for Gulf Oil. In May his legendary Party 1 moved back into Mexico, a country permanently rocked by revolutions. The year 1928 saw Geussen- hainer’s crew in Persia. The Anglo-Persian (later BP) no longer wanted to stand on the sidelines. Soon three crews were bustling about in the region. Surveying in the rugged Bakthiari mountains demanded the utmost of men and method. Subsequently work was carried out for the Turkish Petroleum Company in Iraq. The Egyptian government also made use of the new technique.
The chase had begun
Yet that was all by the by. The main battlefield was still in the US. Up to four SEISMOS crews operated simultaneously there. Party chiefs, besides Geussenhainer and Mintrop, included other renowned scientists such as Ernst Cloos, Friedrich Trappe, Carl Schmidt, Wilhelm Kolb, and A. Thomas. Mintrop talked of 22 salt structures discovered by SEISMOS in the US up to 1930. The very prolific oil field of the East Hackberry salt dome too was one of them. No less than nine companies used the services of SISMOS in the US from 1923-30. Something big was set in motion.
How did the oil country America react to such spectacular events? The press was full of it. But decisive were the consequences of this revolution. Here is what two competent chief witnesses of this epoch had to say.
O. Scott Petty, cofounder of the Petty Geophysical Engineering Company (now integrated into Halliburton Geophysical Services) relates the formation of his company in the brochure Seismic reflections Petty, then an engineer in Dallas, cites a letter that he received on March 25, 1925 from his brother Dabney, a geologist in Austin. Petty sees this note as “The Letter That Sparked the Beginning,” that is, the beginning of his company:
- Scottie, I am going to enclose a copy of a paper that the SEISMOS
- people put out-who are furnishing the Gulf with their seismographs...There
- are only three companies using them now in the
- Gulf Coast. But the others are working on them and no doubt will
- soon be using them.. .I am wondering if you would spend a few of
- your spare moments in studying the method and see if you can
- learn to interpret the readings.. .I am going to be blown up so far
- as economic geology goes if I don’t get lined up with one of these
- instruments.. .if you could learn how to use one we could do a great
- business doing consulting work.. .
The chase had really begun. The second chief witness is no less than Everette Lee DeGolyer, the most important American oil geologist of his time “Mr. De” spoke candidly of Mlntrop’s success on the Gulf coast:
- . ..I was inclined to be skeptical with regard to the possible value
- of the seismic method. Repeated successes of the SEISMOS crews
- for the Gulf, however, soon convinced me that the method was one
- to be reckoned with...During 1925 practically all the commercial
- work was being done by SEISMOS. In November of that year three
- crews were operating for the Gulf and one crew for Marland.
DeGolyer had been converted from “Saulus” to “Paulus.” And “Paulus” DeGolyer did not require any more proof of the system’s effectiveness. He started to act. Together with Karcher and advised in scientific matters by the brilliant inventor Reginald Fessenden, he founded the Geophysical Research Corporation (GRC) in 1925 as a subsidiary of Amerada Oil. The legendary “Amerada tree” was planted. The company was to become the origin of several of the most successful American geophysical organizations. Mintrop had shot awake the oil giant USA. A long line of witnesses to these events could be given; however, the citations of Petty and DeGolyer should suffice.
Scouts and Gunmen
It proved of little value that Mintrop protected his seismographs like a state secret and had them guarded. He forbade his employees to make technical or scientific drawings which could have fallen into the wrong hands. Karl Roepke, a long-standing colleague of Mintrop, bears witness to “The Boss” having once frisked his suitcase and found a bundle of very private letters, made evident by a pink ribbon. Weighing the bundle undecidedly in his hands at last, only at Roepke’s earnest request, hesitatingly put it back in the case with the words: “Well, I believe you this time.”
Mintrop’s fears were well founded, as the correspondence be- tween the Petty brothers proves only too clearly. His technique was protected by patent in the US in 1926, but what did that mean? Protection was illusion, be it by gunmen or by law. Soon, too many oil companies knew the instrumentation and the technique, its strengths and its limitations. This state of affairs was seen by Sweet as follows:
- The German seismograph parties in the year and a half that they
- were alone in the field, employed guards armed with shot guns
- with instructions to shoot anyone who approached the tents in which
- the mechanical seismographs were set up. These armed guards were
- also used for the purpose of making sure no one stole any part of
- the equipment. Other companies did scout the Germans but usually
- with the aid of a pair of binoculars and at a safe distance.
The scouts were not only after Mintrop’s equipment and technique, they also wanted the results as a consequence of the peculiar American mineral rights of landowners. Party Chief and Wiechert pupil Wilhelm Haubold described this facet of the archaic seismic era in his memoirs:
- We were seldom longer than 14 days in one place and were often
- dispatched between Texas and Louisiana, chased by the scouts
- whose job it was to continuously observe our work, enter all our
- survey points in maps and to inform their companies of the state
- of our work. Usually there were several scouts from different oil
- companies after us. At first we looked down at them contemptuously
- as spies, but we soon realized that their occupation was far more
- respectable. It was not long before we were good friends. We
- helped each other and soon the scouts were virtually part of the
- crew. They helped us when we got stuck or they drove for us to
- the other points to check the time and we pulled them out of sticky
- situations so they could keep up with us. Problem was that the
- presence of the scouts meant we had to work carefully. When we
- found an interesting object we could not simply lay out more survey
- points than usual, at least not with the knowledge of the scouts;
- because as soon as the points were set closer the scouts’ alarm
- would bring crews from other companies rolling into the area.
- These crews too were from SEISMOS, but we were not allowed to
- have anything to do with them and had to stay in different hotels
- when by chance we were at the same place.
Phoenix from the ashes
Mintrop’s successes did not encourage only the American oil industry but also those individuals whose seismic reflection experiments did not lead to the breakthrough in 1921 in Oklahoma at Vines Branch: Haseman, Karcher, Engelhardt, Eckhardt and Burton McCollum. This group was probably implied when Donald Barton wrote:
- Their results at the time seemed rather negative but very recent
- work shows that the apparent failure at that time was due largely
- to lack of encouragement and to limited financial resources. The
- initial impetus to the present extensive use of the seismic (or sonic)
- method is due very largely to L. Mintrop and his SEISMOS company..
- .The discovery by the seismograph of several salt domes in
- 1924 gave great impetus to the use of the method..
Those who succumbed in 1921 liquidated their Geological Engineering Company and disbanded in all directions, but Mintrop’s sensational success made some people rethink their negative point of view. DeGolyer founded the GRC together with Karcher. The oil man Marland, normally open to all new ideas, had sponsored the Vines Branch project half-heartedly at first, then dropped it altogether, hiring a Mintrop crew instead. But now he remembered those eggheads of the 1921 project, and he managed to hire Haseman and Eckhardt to establish his geophysical department. McCollum went to the Atlantic Refining Company with all the patents from the liquidated company. The seeds were sown. The mightiest industry of the mightiest country on earth had become aware of an immense potential.
From 1923-25 Mintrop dominated the field in the US. But in 1926 the first GRC refraction crews appeared on the scene. SEISMOS’ fighting years had begun, and they were destined to end in defeat. Germany and Haunover were simply too far away. Sup- plies had to be. sent by ship-Charles Lindbergh had not crossed the Atlantic yet. The German economy was weakened too much by inflation, and the financial basis of SEISMOS was not strong enough to afford expensive R&D projects which were urgently needed. So it was left to GRC to replace the clumsy mechanical/optical seismographs by electrical systems which used the then newly developed vacuum tube for signal amplification. This was a device breakthrough. After just a few months, GRC crews dis- covered the first salt structures. And for the GRC too the flow of discoveries kept on going.
But now another and still greater threat to Mintrop and his company cropped up: a new method, which since Fessenden’s fundamental work of 1914 had become so significant for marine navigation-echo sounding, or as better known to our guild, reflection seismics. For if the echo sounding technique could be applied also to make the earth’s crust transparent, then an instrument would be available for sampling the subsurface in its multifarious forms. For the petroleum geologist these would be the spectacles enabling him to look into the crust. And he got his spectacles, even if the lenses were still cloudy in the first decade. But soon he got them cleaned.
GRC achieved the big breakthrough, Karcher playing a decisive part. In 1927 initial tests were carried out-successfully. And two years later, the first four GRC reflection crews were under con- tract. Reflection seismics , the possibilities of which Mintrop long did not recognize-the most fatal misconception of his career- started to push refraction seismics into second place after 10 years of domination.
By 1930 SEISMOS’S lead had gone, the company’s historical pioneer function was at an end. Contracts were no longer being renewed. On top of that came the Great Depression, which was hurrying toward its climax. Mintrop and SIZISMOS had lost their overseas domain in the US. New forces were pushing forward with new ideas at the head of development. The oil giant America considered its financial and intellectual resources, then took a firm hold of applied geophysics.
Mintrop, the man
Another battle ended in 1930, albeit more successfully. Mintrop wrote:
- The initial years of SEISMOS were particularly difficult in that I had
- to defend the German patent concerning the seismic technique
- against stubborn attack from the very beginning. This fight lasted
- uninterruptedly for 9 years until a decision in our favour was
- reached on 28 June 1930 by the German Court.
Mintrop left SEISMOS in 1933. Already in 1928 he had been offered a chair as professor for mining surveying and geophysics at the Technical High School and University of Breslau, and so returned to teaching. Up to the beginning of the war he also acted as a consultant for Texaco, the company which had bought his patents. This made it necessary for him to travel to America once a year. And it happened that he was on board the Bremen when the ocean liner in a daring ride broke through the British blockade in order to return to Germany after the outbreak of the war. any, but the good doctor always made up for it by a friendly gesture whatever was lacking in the enunciation.
In 1948 Mintrop retired from professional business life and returned to the parental estate near Essen, the right place for him to spend his remaining years. Nevertheless, even after his retirement, he kept in touch with the scientific world by maintaining active membership to numerous geophysical, geodetic, and civil corporate bodies as well as by visiting important conferences.
He was frequently honored. The Mining High School of Leoben (Austria) conferred an honorary doctorship upon him. Just a few weeks before his death he received the German Order of Merit. The bestowal of the SEG Honorary Membership must have given him profound satisfaction. He and his great opponent, DeGolyer, were the first to be honored in this way by the Society, then still in its foundation year of 1930. And the two great masters of applied geophysics have yet another date in common-the year of death. Mintrop died on January 1, 1956.
Karl Lehmann, friend and comrade-in-arms during the decisive formation years of SEISMOS, described Mintrop as a broad-shouldered fellow around 5 feet 9 inches tall with an immense head (that could have been sculptered by Ernst Barlach) under a floppy hat covering a mighty forehead and an exaggerated hook nose. He possessed never-ending enthusiasm for work and he was mathematically brilliant. His breath-taking ability in mental arithmetic as well as his virtuosity in the use of log tables and slide rules would have been irritating to those of us who scarcely risk a mathematical statement without first consulting a calculator. Lehmann also testifies that Mintrop was excellent at drawing, undoubtedly an inheritance from bis granduncle, the painter Theodor Mintrop, after whom a street is named in Dusseldorf. What did his American colleagues have to say about him? What about his famous ever-smouldering cigar? Eckhardt wrote in Mintrop’s obituary
- All told Dr. Mintrop made 19 visits to the United States. Those of
- his friends who were fortunate to he visited by him will remember
- the cigar invariably clenched between his teeth, and remaining there
- throughout the conversation. This did not help the intelligibility
- any, but the good doctor always made up for it by a friendly gesture
- whatever was lacking in the enunciation.
And how was Mmtrop seen as businessman and company director? Sweet remarked not without some irony
- DeGolyer, Mintrop and Karcher were all supersalesmen.. .Yet it is
- quite possible that Ludger Mintrop was the greatest of them all.
We will leave the last word to his friends and colleagues as handed down from them, either verbally or in writing. When they spoke of Mintrop then only with great respect and even greater affection-respect for the scientific genius, affection for the man. Geussenhainer wrote about Mintrop’s crew visits: “He didn’t come to us as the ‘boss’, rather as a friend.” Comradeship and his real caring for all those he was responsible for must have been overwhelming; this is attested to by numerous letters to former colleagues written in captivatingly clear handwriting. They reveal his strong, reliable character, but also the wisdom of a cosmo- politan. Occasionally they are tinged with bitterness and even with a touch of resignation: “There is timefor everything, and pioneer times are always short.
About 1902, a young PhD candidate in Germany, set up an experiment to create a “man-made” earthquake. His name was Ludger Mintrop. He built a tall metal tower (about 50 feet?) and dropped a large iron ball, thereby creating a man-made earthquake. He recorded the event and conducted the experiment several times.
A seismograph invented and developed in Germany by Ludger Mintrop, a distinguished pioneer in the development of exploration geophysics. Very likely it is responsible for the first discovery by the seismic method. This was the discovery of the Orange saltdome in the Texas Gulf Coast. Except for a battery to power an electric lamp, it is entirely mechanical.This seismograph was designed for the seismic refraction exploration method.
The traveltime of seismic waves from a dynamite blast, in a borehole several feet below the earth's surface, to the seismograph is recorded. Velocity of these waves increases with subsurface depth and, thus, the greater the distance between the source (that is, the dynamite blast) and the seismograph, the greater the penetration depth of the waves. Any abnormal change in velocity along the travel path of the waves will alter the traveltime and, thus, indicate an anomalous rock type. The mechanical seismograph was employed in the 1920's and early 1930's (the initial period of geophysical petroleum exploration) almost exclusively for the detection of salt domes in the Texas-Louisiana Gulf Coast region. Here, salt has penetrated overlying sedimentary rock layers to form domes. Porous rock layers that are pierced and bent upward by the rising salt are excellent traps for upward migrating fluids that are halted when encountering the nonporous salt. Seismic wave velocity in the salt is as much as two and one-half times that in the surrounding rock layers.
The reduced traveltime of seismic waves traversing the salt dome was readily detected in the seismic refraction method, especially for shallow domes that penetrated to one or two hundred feet below the earth's surface. By 1930 the majority of salt domes in the Texas-Louisiana Gulf Coast region penetrating to shallow depths had been discovered by the refraction method, by the torsion balance or by a combination of the two.The Mintrop mechanical seismograph consists of the two units shown, a detector of seismic waves on the right and a recorder of these waves on the left.
The detector consists of a metal ball suspended by a spring. When the detector is planted on the earth's surface, vertical movement of the mass due to arrival of seismic waves deflects horizontally a mirror. The mirror is attached at the apex of an inverted cone which is an upward extension of the mass. A beam from a light source in the recorder directed to the mirror is reflected back to moving light-sensitive paper; thereby, recording motion of the detector's ball and, thus, the seismic waves. The instant of the dynamite blast was radioed to the recorder and onset time of the seismic wave was measured from timing marks on the recording paper. Commencing in the early 1930's, mechanical seismographs were supplanted by electronic recorders and electromagnetic transducers, called seismometers, which are several times more sensitive. These were used in the seismic reflection method which proved much more effective than the refraction method in the search for petroliferous subsurface structures commercial seismograph and its successful application was the catalyst for initiation of seismic exploration worldwide. It was the first commercial seismograph and its successful application was the catalyst for initiation of seismic exploration worldwide.
Later, he developed a mechanical seismograph that was introduced during WWI to locate enemy artillery batteries. It recorded ‘first arrivals’ of refractions. He started a company called Seismos and had several early contracts in the US.