Editing Reflection seismology (section)

==History==
[[File:Workers performing seismic tests, Seismic Explorations, Inc..jpg|thumb|upright|Seismic testing in 1940]]

Reflections and refractions of seismic waves at geologic [[Interface (matter)|interfaces]] within the Earth were first observed on recordings of earthquake-generated seismic waves. The basic model of the Earth's deep interior is based on observations of earthquake-generated seismic waves transmitted through the Earth's interior (e.g., Mohorovičić, 1910).<ref>{{cite journal |doi=10.1175/BAMS-88-5-693 |url=http://www.croatianhistory.net/etf/orlic.pdf|title=Early Observations of Rotor Clouds by Andrija Mohorovičić|journal=Bulletin of the American Meteorological Society|volume=88|issue=5|pages=693–700|year=2007|last1=Grubišić|first1=Vanda|last2=Orlić|first2=Mirko|bibcode=2007BAMS...88..693G}}</ref> The use of human-generated seismic waves to map in detail the geology of the upper few kilometers of the Earth's crust followed shortly thereafter and has developed mainly due to commercial enterprise, particularly the petroleum industry.

Seismic reflection exploration grew out of the [[seismic refraction]] exploration method, which was used to find oil associated with [[salt dome]]s.<ref name="Applied Geophysics 1976">{{cite book |last=Telford |first=W. M. |display-authors=etal |title=Applied Geophysics |publisher=Cambridge University Press |year=1976 |page=220}}</ref> Ludger Mintrop, a German mine surveyor, devised a mechanical seismograph in 1914 that he successfully used to detect salt domes in Germany. He applied for a German patent in 1919 that was issued in 1926. In 1921 he founded the company Seismos, which was hired to conduct seismic exploration in Texas and Mexico, resulting in the first commercial discovery of oil using the refraction seismic method in 1924.<ref>{{cite book |last1=Sheriff |first1=R. E. |last2=Geldart |first2=L. P. |year=1995 |title=Exploration Seismology |edition=2nd |publisher=Cambridge University Press |pages=3–6}}</ref> The 1924 discovery of the Orchard salt dome in Texas led to a boom in seismic refraction exploration along the Gulf Coast, but by 1930 the method had led to the discovery of most of the shallow [[Louann Salt]] domes, and the refraction seismic method faded.<ref name="Applied Geophysics 1976" />

After [[WWI]], those involved in the development of commercial applications of seismic waves included Mintrop, [[Reginald Fessenden]], [[J. Clarence Karcher|John Clarence Karcher]], E. A. Eckhardt, William P. Haseman, and Burton McCollum.  In 1920, Haseman, Karcher, Eckhardt and McCollum founded the Geological Engineering Company.  In June 1921, Karcher, Haseman, I. Perrine and W. C. Kite recorded the first exploration reflection seismograph near [[Oklahoma City, Oklahoma]].<ref name=rs/>{{rp|4-10}}

Early reflection seismology was viewed with skepticism by many in the oil industry. An early advocate of the method commented:

:"As one who personally tried to introduce the method into general consulting practice, the senior writer can definitely recall many times when reflections were not even considered on a par with the divining rod, for at least that device had a background of tradition."<ref>{{cite journal |last1=Rosaire |first1=E. E.  |last2=Adler |first2=Joseph H. |title=Applications and limitations of the dip method |journal=Bulletin of the American Association of Petroleum Geologists |date=January 1934 |volume=18 |issue=1 |page=121}}</ref>

The Geological Engineering Company folded due to a drop in the price of oil. In 1925, oil prices had rebounded, and Karcher helped to form Geophysical Research Corporation (GRC) as part of the oil company [[Hess Corporation|Amerada]].  In 1930, Karcher left GRC and helped to found [[Geophysical Service Incorporated]] (GSI).  GSI was one of the most successful seismic contracting companies for over 50 years and was the parent of an even more successful company, [[Texas Instruments]].  Early GSI employee [[Henry Salvatori]] left that company in 1933 to found another major seismic contractor, [[Western Geophysical]]. Many other companies using reflection seismology in hydrocarbon exploration, [[hydrology]], [[engineering]] studies, and other applications have been formed since the method was first invented.  Major service companies in recent years have included [[CGG (company)|CGG]], [[ION Geophysical]], [[Petroleum Geo-Services]], [[Polarcus]], [[TGS-NOPEC Geophysical Company|TGS]] and [[WesternGeco]], but since the oil price crash of 2015, providers of seismic services have continued to struggle financially such as Polarcus,<ref>{{Cite web|url=https://polarcus.com/press_releases/polarcus-appointment-of-joint-provisional-liquidators/|title=Polarcus: Appointment of Joint Provisional Liquidators|work=Polarcus }}</ref> whilst companies that were seismic acquisition industry leaders just ten years ago such as CGG<ref>{{cite web |url=https://www.cgg.com |title = CGG: Delivering Geoscience Leadership}}</ref> and WesternGeco<ref>{{Cite web|url=https://www.slb.com/companies/westerngeco|title = WesternGeco}}</ref> have now removed themselves from the seismic acquisition environment entirely and restructured to focus upon their existing seismic data libraries, seismic data management and non-seismic related oilfield services.