D4

The aim of this pro­ject is the geo­phy­si­cal and geo­tech­ni­cal se­abed cha­rac­te­riza­t­i­on, with a spe­cial fo­cus on as­si­gned off­shore con­struc­tion sites (e.g. wind en­er­gy parks), the cor­re­la­ti­on of sur­vey in­for­ma­ti­on with soil strength data, and the stu­dy of lo­cal off­shore struc­tu­re-se­abed in­ter­ac­tions in a mor­pho­dy­na­mic and mi­cro­me­cha­ni­cal sen­se. A new shal­low-wa­ter mul­tichan­nel seis­mic sys­tem will be used to de­ri­ve vo­lu­me and re­flec­tor seis­mic pro­per­ties, which can be com­pa­red with in-situ geo­tech­ni­cal mea­su­re­ments and sam­ples to ge­ne­ra­te sta­tis­ti­cal­ly si­gni­fi­cant cor­re­la­ti­ons bet­ween geo­tech­ni­cal and geo­phy­si­cal data as pre­dic­tive tools for se­di­men­ta­ry site cha­rac­te­riza­t­i­on. New-pipe lay­ing tech­ni­ques in non-co­he­si­ve sub­stra­tes will be eva­lua­ted, de­si­gned and tested. The pro­ject spe­ci­fi­cal­ly ad­dres­ses how up­co­m­ing off­shore foun­da­ti­on ac­tivi­ties may af­fect the dy­na­mic strength of the Plei­sto­ce­ne and Ho­lo­ce­ne se­di­ment. Wi­t­hin the frame­work of re­se­arch area D, this pro­ject deals with an ac­cu­ra­te site cha­rac­te­riza­t­i­on by sur­veys, sam­pling and in-situ mea­su­re­ments, whi­le the com­pli­men­ta­ry pro­ject D1 fo­cu­ses on the en­vi­ron­men­tal im­pact of har­bors and con­struc­tions. Bey­ond the sci­en­ti­fic and me­tho­do­lo­gi­cal chal­len­ges in shal­low wa­ter re­se­arch, the pro­po­sed pro­ject in­tends to pro­vi­de re­le­vant me­thods and data for fu­ture tasks in ma­ri­ne off­shore con­struc­tion work, to keep clo­se con­tact with ad­mi­nis­tra­ti­on units (e.g. BSH, BGR) and sur­vey (e.g. OSAE) and con­struc­tion com­pa­nies, and to build up ex­per­ti­se for stu­dent edu­ca­ti­on in ap­p­lied geo­sci­en­ces.

Multifrequency Seismoacoustic Survey of a planned Wind Farm Area

The seis­mic data of a de­si­gna­ted wind farm area off Bor­kum re­veals that the wind farm area is lo­ca­ted above the eas­tern flank of an up­do­m­ing struc­tu­re, pro­bab­ly a salt dome. The flank is lo­ca­ted in depth of 170 to 280 me­ters. The near-sur­face struc­tu­re is qui­te he­te­ro­ge­neous and cha­rac­te­ri­zed by nu­merous fil­led chan­nels, of­ten cut into each other.

2009-2012

The re­lease of mel­twa­ter from the mar­gins of the Late Qua­tern­ary Fen­no­scan­dian ice sheets re­sul­ted in com­plex net­works of (now bu­ried) Plei­sto­ce­ne tun­nel-val­leys that ex­tend be­ne­ath lar­ge parts of the North Sea and the ad­ja­cent nort­hern Eu­ro­pean low­lands. De­eply in­cised (100-500 m) into most­ly Neo­ge­ne se­di­ment stra­ta, they form a do­mi­nant ar­chi­tec­tu­ral ele­ment of the North Sea se­di­men­ta­ry ba­sin and are a pri­ma­ry cau­se of small sca­le li­tho­lo­gi­cal he­te­ro­gen­ei­ties. Off­shore map­ping ba­sed on seis­mic sur­veys is far from com­ple­te, but has pro­vi­ded evi­dence of mul­ti­ple ge­ne­ra­ti­ons of bu­ried val­leys, in­fer­red to re­cord at least three suc­ces­si­ve cy­cles of con­ti­nen­tal gla­cia­ti­on and in­ter­gla­ci­al ma­ri­ne trans­gres­si­on. The lar­gest known bu­ried val­leys lie in and ad­ja­cent to the sou­thern North Sea and have been ten­ta­tive­ly cor­re­la­ted to the mid-Plei­sto­ce­ne Els­te­ri­an gla­cia­ti­on. The re­cent dis­co­very by MARUM sci­en­tists of a so far un­k­nown ma­jor E-W tren­ding bu­ried val­ley in the SE North Sea po­ses new mul­ti-di­sci­pli­na­ry ques­ti­ons with re­gard to the ages of cross-cut­ting fea­tures, their in­fill ar­chi­tec­tu­re and li­tho­lo­gy, the ori­en­ta­ti­ons and dy­na­mics of for­mer ice mar­gins, the num­ber and na­tu­re of in­ter­gla­ci­al ma­ri­ne trans­gres­si­ons and the miti­ga­ti­on of geo­tech­ni­cal risks. The lat­ter is of eco­no­mic im­port­an­ce as li­tho­lo­gi­cal he­te­ro­gen­ei­ties in shelf se­di­ments in­du­ced by such val­leys, com­mon fea­tures also in other for­mer­ly gla­cia­ted re­gi­ons, have re­cent­ly gai­ned at­ten­ti­on in off­shore wind park plan­ning as po­ten­ti­al geo­tech­ni­cal risks. 

                      

Figure 1. Seis­mic sec­tion through the re­cent­ly dis­co­ve­r­ed E-W tren­ding bu­ried val­ley in the Ger­man Bight.